Re: [AMRadio] Antennas
The other interesting thing about HiQ antennas is that the final must be neutralized very well else it will tend go into some weird oscillations with the slightest mistuning and may oscillator with modulation or at least have significant phasing products causing the signal to be much wider than it otherwise would be. I am not sure, in the case where neutralization is perfect, if HiQ tuning would cause phasing products with modulation near the slope of the tuning curve or not. It seems to me that it would, but the attenuation of the slope may cover that up. John -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of D. Chester Sent: Tuesday, June 22, 2010 10:36 AM To: amradio@mailman.qth.net Subject: Re: [AMRadio] Antennas There have been some interesting cases with short loaded antennas in the BC band, the bandwidth has occasionally been so narrow that the AM sidebands become attenuated! Not going to see that effect in the amateur bands unless someone is running an antenna only a few feet long!! Bernie W8RPW I almost have that situation on 160m when I use my 80m dipole, fed with open wire line and balanced tuner. I can move maybe +/- 5 kHz before I have to retune. Using that antenna set-up is like being crystal controlled, since I have to go down to the tower to re-set the tuner. Hopefully, by upcoming season I'll have my remote tuning system, with reversible DC motor, so I'll at least be able to QSY within the same band without a trip to t he tower. I hope to eventually make it so I can change bands remotely as well. Don k4kyv ___ This message was typed using the DVORAK keyboard layout. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/ __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Request for Most Common Capacitor Values to be Reproduced
+/- 20% Modern material will make the capacitors smaller than original so I would suggest to go with only 600V .001 .0022 .0039 .005 .01 .022 .039 .05 or .047 .1 .15 .22 -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Todd, KA1KAQ Sent: Monday, May 03, 2010 5:32 PM To: Discussion of AM Radio in the Amateur Service; milsurplus; Boatanchors; National Radio Equipment; Hallicrafters Reflector Subject: [AMRadio] Request for Most Common Capacitor Values to be Reproduced Sorry for the multiple list posting, but time is short and max input is desired. Got a call from a friend this afternoon who is talking with a capacitor manufacturer about producing some caps for the radio, guitar amp, and audio crowd. We've talked about this in the past but never got to it. Now it looks like it will happen. The question is, what values would be the most handy to have supplied into the future for restoring old gear? Obviously we can't do a lot of oddball values as we're mainly looking for values that will sell well and be attractive from a production prospective. The few that popped to mind for me were: .1, .01, and .47 mfd at both 400 and 600 vdc. I also specified axial lead instead of the radial leads found on Orange drops since axial leads are better suited to our needs. I'm looking for other values that are likely to be encountered often enough to warrant production. Maybe 6-12 different values to choose from. These would be caps used for bypassing and such, not filtering. I suspect we could get them 'banded' for the foil side as well if folks feel that is important enough. The meeting is set for tomorrow, so timely input is critical. We're *not* looking for a list of manufacturers who already make caps as we believe more is better in this case. Some values are already getting difficult to find. TNX - ~ Todd, KA1KAQ/4 __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] sdr-iq
Hey Bernie: This is just a suggestion of what you might check into. I am not familiar with the radio but have heard other brick radios that sound pretty good. Concerning the computer, it is possible, although you would not generally want it, to listen to the recorded sound while recording and at the same time listen to the input. Obviously the recorded audio will be slightly delayed from the input causing an echo sound. Most sound cards will record at the same time they are playing something, and have a separate set of controls for recording than for playback however both sets may have a listening level control. Just a suggestion on something to check. John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Bernie Doran Sent: Wednesday, February 10, 2010 12:03 PM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] sdr-iq I purchased an SDR-iQ about five weeks ago and while it performs great in a number of areas it seems to be poor in the audio demodulation, at least on AM, I am getting what sounds like a low level echo and a general artificial quality of sound, my 75A2 sounds much better and that certainly is not good quality audio. it is difficult to copy a moderate level AM signal. the computer plays DVDs and CDs fine and sounds good. I talked to the store that I purchased it from and they said they have heard this before and that I should not expect it to sound like a VT receiver! that was a shock, what did I buy it for?. computer is a single core 2.8 gig, it shows it running at about %75. any one else use these things? or have experience with the Flex 5000a? Bernie __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
[AMRadio] Digitizing old records
Not exactly AM radio stuff but it sort of falls in the category of old technology meets the new world. If the list moderator wants to kill this I will certainly understand. We could discuss it separately. I use a modern turntable with 33/45 RPM settings some of the real new TT's do have 78RPM (it is becoming a thing to do). Having the proper stylus is important because it fits the groove and can be set to track a little heavier than a gram. Be careful not to track to heavy, the cartridge may not like it. A lot of the old 78RPM records did not use the standard RIAA equalization of today. There were many different EQs used in those days. Having a 24 bit/96K sound card is a plus for computer recording because you don't have to worry about getting the levels set just right. Just about any visible thing that you can see on the display will be using more than 16 bits in the 24 bit format. This gives you plenty of head room to manipulate the recording latter using the recording software's features to get the sound just the way you want it whether it is RIAA or not. You can even record it at 45RPM and adjust the speed with the software later and re-EQ. After you have it the way you want it to sound then the software will allow you to normalize the recording and then save it to 16 or 24bit format. 16 bit format for CD audio Recording software: Many types are available. Audio Audition by Adobe is what I use - $300 - a little expensive but pretty good. A Canadian company called Goldwave - free trial 40 dollar purchase probably the best bet. I used it before I got Audition. Audacity - Free - I don't know about its EQ and other feature capabilities This is all not recommended on a computer that has glitches or is slow. Good Luck John -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of George Brand Sent: Friday, January 22, 2010 3:41 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] 78 records I have a real Edison that almost caused a divorce between my Grandparents as Grandma bought via the devilON CREDIT! (oh horrors) Apparently Grandpa had a royal fit and went down to J.L. Hudsons the next morning and paid if off. I have four drawers full of disks and want to move them to digital without harming them. Any guidance? I see there is a stylus marketed for this purpose, any experience?? George __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] OT : Paid Hams during Drills
I am a little confused here, as to what would be changed. 1. Are Hams presently not permitted to participate in these preparedness and drills Or 2. Are they not permitted on behalf of their employer. 3. Or, are you saying that an employer can request, as part of your job description and pay grade, that you participate. The ARRL info, on that page, is very vague on this (as usual) as there does not seem to be any other info about it on the web page, or did I just not see it among all the BS. John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of WA5AM Sent: Tuesday, January 19, 2010 11:46 AM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] OT : Paid Hams during Drills I know this does not directly involve AM, however it is something that could set a precedent and change our hobby forever if we don't take a stand and tell the ARRL not to allow a petition for rule change. As some of you may know, the ARRL board of directors have met and decided to request the staff petition the FCC to make a change to Part 97.113(a)(3) to permit amateurs, on behalf of an employer, to participate in emergency preparedness and disaster drills that include Amateur operations. To quote a very good ham friend of mine, ...I feel like we have been sold out, sucker punched! I can't believe a majority of ARRL members support this issue. The article is here: http://www.arrl.org/news/stories/2010/01/19/11294/?nc=1 I think ANYONE should be able to operate during a REAL emergency, and that is already in place. Anyone citizen can use any public service radio to call for help. I have no problem with that. We should not take the volunteer out of ham radio. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] OT : Paid Hams during Drills
Opps: Sorry Bob I did not mean to send that directly to you and only you. Here it is again for all with a little more added: I hope I'm not opening a can of worms here! OK, I think I see the dilemma now, I must say I have mixed emotions here. I see the necessity but I can also see where it could start a trend. I'll need to mull this over a little. I always thought that Hams who worked for anything like a law enforcement or fire and rescue could do what was needed in the way of training to better serve the public but I guess their hands were tied during working hours unless they had a separate volunteer to push the microphone button for them. Is this prevention currently enforced to prevent commercial use of amateur radio? How does it? I would assume that a policeman taking part in a drill, on police time, would use his own call letters would not solicit for the police department. I have been on the job many times driving around town doing my regular job on a wage and have been known to use the repeaters and 40 years ago even check into the old central gulf coast hurricane net once or twice. When did all that become against the law? So part of me wonders if additional regulation is even necessary. Where is the law they might or I have been in the past breaking? Still undecided John __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] HRO question for the day
Jim After looking over your web document. As I see it then the slew distortion is caused by the RF bypass capacitor's inability to discharge fast enough to follow the shape of the audio as it falls. Or, you might say the inability of the load resistor to discharge the capacitor fast enough. If that is the case then it probably effects the higher modulating frequencies more that the lower ones. The Audio bypass is chosen to reduce the RF component of the rectified output to some acceptable value. If that is true then the circuit design could be improved by starting with a higher IF frequency. I would think that the greater ratios of RF to audio frequency would lend its self to a lower time constant there by extending the frequency range of the less distorted audio, Assuming I am on tr5ack here, perhaps one thing that might help is a full wave detector. Two diodes on a center tapped secondary IF XFMR. A smaller bypass capacitor could be used because the RF ripple would be twice the original IF frequency. Am I on track with any of this detector thinking? Do active detectors or DBL Bal product detectors have similar problems? My guess is that they do, but probably not as noticeable except at lower RF to AF frequency ratios. I know many folks that would say it isn't that important and to some degree they are right but it doesn't stop me from trying to understand and design something that is a little better. My fun in this hobby is in the design and modification aspect. Even if no one can tell the difference, it helps me to understand. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] HRO question for the day
I can see a small amount of contact bias being generated by the 6H6, 6AL5, etc. But that would be easy to compensate with divider from the cathode bias of the output tubes or any small positive source. I guess they may have been looking for an easy fix to get the S-meter to zero. This is all very interesting but why not just solder in a Germanium 1N64 or a NTE109 or Silicone NTE177 or even a NTE519 with 4 ns recovery time. I pulled the 6AL5 out of my HQ170 and went to diodes. Saving 150ma of heater current W. I ask this sincerely because I really don't know. What would be the disadvantage of using small signal solid state diodes as long as the IF frequency isn't too high. John __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
[AMRadio] Reactance Calculator
Found this recently http://www.indianabiomedical.com/Calculator/XLCcalculator.html John __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] I need som advice
That 290-262 looks like a nice deal Bob, I may have to get a couple for replacements in some stuff around here. John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Robert Nickels Sent: Monday, October 19, 2009 7:17 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] I need som advice http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-262 While the frequency response of this $17 woofer is given as 74-5000 hz, it might sound pretty good. If you wanted more highs, you could try the approach used by Jensen and others who used to make full-range speakers by suspending a smaller PM speaker across the cone with a simple series capacitor crossover to handle the midrange frequencies. 73, Bob W9RAN __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] I need som advice
Hey Jim, ya might look at ceiling speakers to mount in the original enclosure. Even if smaller driver the ceiling mount may make up the diff and some of the modern speakers sound real good. Everything today is for a lot of power, as in guitar amps, that is what drives the price up. You can't just buy a 10 watt 10 inch speaker any more or they seem to be hard to find anyway. 73, John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Any amplifier suggestions?
Todd, Typically the linear amp will be the fewer parts and expense but with less output than a full plate modulated class C rig per a given tube. One of the simplest tetrode linear systems is to put a 50 ohm load resistor right on the grid of a big jug like a 4-1000 or a pair of 4-400s and use a zener to bias the cathode circuit or fil return. It will also require a screen supply. The idea in all of this is that if the grid is loaded with a 50 ohm dummy load, then it will not require tuning. The small amount of input capacitance will be negligible on the lower freq bands. And it should not require neutralization. OTH, If you are going linear with a triode or triode connected tetrodes then you will want to go to a grounded grid linear. No screen supply, no neutralization, but does require more drive and/or may require drive tuning. You may expect very poor plate efficiency in any linier amp that is tuned properly to work with an AM input. If you're looking for old style circuits that are proven to have the most output with the least plate dissipation (smallest tubes) then plate modulated full class C finals with push pull class B modulators is best. More work more parts, but well worth the time and effort in the long run. My favorite in small legal limit stuff would be a pair of 812s push pull class C, modulated by a pair of 811a is class B. -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Todd Carpenter Sent: Monday, October 05, 2009 9:30 AM To: AMRadio@mailman.qth.net Subject: [AMRadio] Any amplifier suggestions? I am interested is a simple design hf amplifier for am cw on 160-80/75-40. These are the bands i operate on where the extra power would help. Fewer parts count the better. Ultimately lower cost the better. I have power supply parts and believe that i can generate around 2000 volts. I am slowly researching tubes and am leaning toward 2 or 4 tubes that can basically generate lots of watts at half to two thirds their ratings to prolong their life span. Perhaps tubes such as 811's, 810's, 833's, 4-400's. I am open to suggestions. I will need to build or acquire a heavy duty matching system as part of the amp. My goal is at least 300 Watts AM. I do not want to mess with systems that require cooling other than fans. I am not interested in modes for this amp other than am and cw. It will almost exclusively be used for am as i rarely use more than 5 watts on cw any way. Simpler cheaper is better for me. I appreciate your suggestions. Todd __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Microphone recomendation
Very nice combination Don. Have you decided what those big triodes tubes are that I gave you, characteristics, etc., and speaking of Microphones have you found one of those connectors or a part number. As for the 12AX7s, I have always wondered if a guy could build a SS replacement with the same anode/drain characteristic curves or close as the 12AX7. FETs have a very high input resistance, They can be configure with a higher leak resistor than tubes without effecting the bias because they don't have the contact or collision bias effect. They don't have the typical triode curves, but are more like a pentode curve set (constant current set as it is sometimes called). It may be possible to correct this through feedback biasing or depending on the circuit it will be used in, it may not matter. They may also require some over voltage protection to prevent breakdown when someone plugs in a microphone and a high pulse is placed on the input. I feel that all of these things can be overcome and good product resulting. I can see it now SS-AX7 by Matsumushisomma Maybe I'm behind and it is already here! John __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Power Transformer as Mod Transformer (was: Seventy Fiver)
That is a great article Brian, and Lee. I have done this a long time ago. They work really well especially with the choke. They also make pretty good output XFMRS for HiFi and PA. The old 200 watt XFMRs we once saw in the old TVs are not as available as they once were. Prior to the Switch Mode solid state supply that Modern TV use, but after the big XFMRs and the 5U4s, there was a lot of constant voltage XFMRs in TVs especially the hybrids. These are recognizable because they were always accompanied with a 2-10 MF 600V capacitor in a can, possibly oil filled, used on the saturation winding of the XFMR. I have found them to make very good regulators for RCVRs, VFO, etc. They will maintain the supply voltage constant to the VFO plate and heater even if the mains drop to 100V when a big rig is key to XMIT. This way you don't slide up the band while XMITing. John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Bry Carling Sent: Thursday, September 24, 2009 4:50 AM To: glowb...@piobaire.mines.uidaho.edu Cc: flboatanch...@yahoogroups.com; Discussion of AM Radio in the Amateur Service Subject: [AMRadio] Power Transformer as Mod Transformer (was: Seventy Fiver) There is a great article on how to use power transformers like that - as a mod transformer - available on line for free - by Tim, WA1HLR I hope it helps you - http://www.amwindow.org/tech/htm/tvtomod.htm LEE, W0VT writes: I went to Lowe's this evening and picked up some oak lumber to build up some Slat Board Transmitters. (They sell oak down to 1/4 inch thick to be used for the slats. I plan to screw the slats to the main oak end panels with brass screws and then stain and polyurethane the wood. I plan to build up one chassis as a 6V6 oscillator with pi-net. Another with a 6AG7 with pi-net. Then compair the output of the two plus check crystal current on both of them. Then I plan to build up another one with a 6AG7 osc and 6L6 amp with pi-net and plug in coils. Then I plan to build power supplies for these on slat board chassis and maybe use 5R4 rectifiers as I have some of these around here. Then maybe a modulator for the 6AG7/6L6 rig. For a modulation transformer I am thinking of trying a 70 volt or 25 volt line transformer or/and a power transformer having it's core restacked in E and I configuration with a gap between the two. The projects won't cost much and I think they will be great looking. I'll use broadcast band variable caps in the pi networks. (Duals for loading and singles for the tank circuit.). Maybe use some rigid clear plastic tubing over old tube sockets for the plug in coils. Lee, w0vt - Original Message - From: Charlie , W5COV To: glowb...@piobaire.mines.uidaho.edu Sent: Wednesday, September 23, 2009 9:04 PM Subject: GB Seventy Fiver Group , the topic came up a while back with thoughts of building a 75 meter version of the Twoer etc. Heath line . Did it fall by the way , because of a lack of interest , or did anyone do any type of development on something like this ? I am ALWAYS looking for a glowbug project to build , that isn't real complex and won't break the bank. A transceiver to put on the air would be a nice project . I have a bench overflowing with homebrew transmitters , mostly CW . Being on a fixed income , I like projects that parts can be readily obtained for at cheap prices . With my medical problems , I lack the design ability , that I used to have . The medications and disease cause a technical medical term called brain fog . So I depend HEAVILY , almost exclusively ,on other peoples designs . So if you know of a simple transceiver design that glows and is AM , please point me to it . Thanks for allowing me to be a part of the best group I belong to !! 73, Charlie , W5COV __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an
Re: [AMRadio] Hallicrafters R-12 speaker
I agree Bob. Maybe Brian intends to put a pair of 805 between the receiver and the speaker and play some guitar. At any rate I'm sure he has his reasons. I might go with this one (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-486), and even it is an over kill but selection of 12 inch speakers with less than a 20 watt rating are few and far between. Many times I will cut a board to fit where the speaker goes and then mount a smaller speaker to the board. In most cases the smaller speaker has better sound due to modern manufacturing and tech specs than the older one. http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-486 73, John -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Bob Peters Sent: Friday, September 04, 2009 6:02 PM To: 'Discussion of AM Radio in the Amateur Service' Subject: Re: [AMRadio] Hallicrafters R-12 speaker WOW That is way overkill for Ham Radio ...Bob -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of WA5AM Sent: Friday, September 04, 2009 5:45 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Hallicrafters R-12 speaker This one here: http://www.parts-express.com/pe/pshowdetl.cfm?DID =7Partnumber=290-834ctab=2#Tabs 73 Brian On 9/4/09, John Coleman j...@pctechref.com wrote: I'm curious Brian, what is the one that you intend to get? John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto: amradio-boun...@mailman.qth.net] On Behalf Of WA5AM Sent: Friday, September 04, 2009 4:42 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Hallicrafters R-12 speaker Thanks John. They appear to have one that will work very well, and the price on their speakers is darn good! 73 Brian On 9/4/09, John Coleman j...@pctechref.com wrote: Brian I buy most speakers from Parts Express. They have a lot of audio parts and equipment. (http://www.parts-express.com) Good Luck John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amra...@mailman.qth.ne t/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html -- Brian Sherrod, PA My website: http://w5ami.net Arkansas Amateur Community Forums - http://w5ami.net/forums wa...@arrl.net __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amra...@mailman.qth.ne t/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amra...@mailman.qth.ne t/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html -- Brian Sherrod, PA My website: http://w5ami.net Arkansas Amateur Community Forums - http://w5ami.net/forums wa...@arrl.net __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amra...@mailman.qth.ne t/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net
[AMRadio] Test
Please excuse and ignore - test new email provider __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Hallicrafters R-12 speaker
Brian I buy most speakers from Parts Express. They have a lot of audio parts and equipment. (http://www.parts-express.com) Good Luck John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Hallicrafters R-12 speaker
I'm curious Brian, what is the one that you intend to get? John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of WA5AM Sent: Friday, September 04, 2009 4:42 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Hallicrafters R-12 speaker Thanks John. They appear to have one that will work very well, and the price on their speakers is darn good! 73 Brian On 9/4/09, John Coleman j...@pctechref.com wrote: Brian I buy most speakers from Parts Express. They have a lot of audio parts and equipment. (http://www.parts-express.com) Good Luck John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html -- Brian Sherrod, PA My website: http://w5ami.net Arkansas Amateur Community Forums - http://w5ami.net/forums wa...@arrl.net __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] 100TH and 250TH advice and or comment
I think bringing filaments up slow is a good idea. At one time we used a varister device in the degaussing circuit of the old TVs. These little round resistors would have about 100 ohms resistance when cold but would go down to a tenth of an ohm or less when hot. They make a very good auto starter for heaters. I use them in the primary of the filament XFMRs. But for long periods of setting a variac might be best. 73 John -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of crawf...@surfmore.net Sent: Tuesday, August 25, 2009 9:43 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] 100TH and 250TH advice and or comment John Mohn was W5MEU. I remember him talking about that one night over 20 years ago.I have an old 450TL that I want to use. I guess I need to bring it up slowly with a variac feeding the filament transformer to keep the inrush current from wrecking the filament, or is that an issue? Joe W4AAB I think there is at least some truth to this Lee, but I am not sure of why. By the same token though I have run 250ths for quite some time and with many hours of no use both winter and summer without air conditioning. They seem to always work the same even though I may only fire them up once or twice a year (much to my dismay). So I really don't have any good answer for this. If all the tubes in question were assemble into the 610 at the same time then maybe you could just pass this off as it was finally time that the air leak got to them. Don, K4KYV and Tim, WA1HLR have discussed this sort of thing quite a bit as well as deterioration of cathode coatings in both directly heated tubes and indirectly heated tubes. You may want to consult with them about this. One thing is for certain, if the final tube is weak then it will be very difficult to get it to produce a wave form output that matches the audio wave form, and it gets worse as the power demand goes up. 73 John -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of LEE BAHR Sent: Tuesday, August 25, 2009 2:20 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] 100TH and 250TH advice and or comment John Moan (forgot his call and spelling) (SK) in San Antonio used to run a few BC-610s. He always rotated his 100TH and 250TH tubes to keep gassing from forming in them. He had about a dozen BC-610s and around 17 R-390A receivers in his shack. I think he used to say it was bad to lie them on their side too. He seemed to know what he was doing and swore the cycling of the tubes was neccessary to keep them alive. He claimed storing these tubes would kill them in time. I am only talking about 100TH and 250TH tubes. Lee w0vt Houston __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] 100TH and 250TH advice and or comment
Do they show color on the plates or gas type ionization color when in use? If they show gas ionization color when in use then they defiantly have air in them and could be caused by overheating due to some malfunction. Maybe they have many more hours on them than you know about. If the plates or just a little red but no gas ionization then the tubes or probably OK. Make sure the grid drive stays up at the recommended level and one way to tell if a tube is losing its conduction is to check the grid drive. If the grid drive falls off considerably when the plate supply is energized then the tube is getting weak. A small amount of grid current fall is normal. The neutralization must be very good to make this check else capacitive feedback will affect your findings. I have used 250ths for some time and have never seen them loose vacuum from any normal use. I did crack one once taking the grid connector off. That was a little heartbreak. Especially when Geoff W5OMR was te lling me to be careful. HIHI 73 John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of rbethman Sent: Tuesday, August 25, 2009 11:07 AM To: AM Radio List Subject: [AMRadio] 100TH and 250TH advice and or comment Question: I have noticed that the 100THs and 250THS that are in their original boxes, either not used at all, or maybe use for less than an hour to test them, seem to be doing fine. Their envelopes are crystal clear an can not see any sort of defect. Then the ones that are in one of the two BC-610s that has the hours on it, even though it last performed flawlessly, now appears to have gone gassy with some milky white inside the envelope. Is this perhaps due to over heating or maybe I should phrase this as the convection cooling of these radios since they do NOT have fans. Ideas? Comments? It has always been metered and watched with a scope for observing waveforms, and the wattmeter is the newer Model Bird with peak reading built-in. (However true they really are!) Bob - N0DGN __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] 100TH and 250TH advice and or comment
I think there is at least some truth to this Lee, but I am not sure of why. By the same token though I have run 250ths for quite some time and with many hours of no use both winter and summer without air conditioning. They seem to always work the same even though I may only fire them up once or twice a year (much to my dismay). So I really don't have any good answer for this. If all the tubes in question were assemble into the 610 at the same time then maybe you could just pass this off as it was finally time that the air leak got to them. Don, K4KYV and Tim, WA1HLR have discussed this sort of thing quite a bit as well as deterioration of cathode coatings in both directly heated tubes and indirectly heated tubes. You may want to consult with them about this. One thing is for certain, if the final tube is weak then it will be very difficult to get it to produce a wave form output that matches the audio wave form, and it gets worse as the power demand goes up. 73 John -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of LEE BAHR Sent: Tuesday, August 25, 2009 2:20 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] 100TH and 250TH advice and or comment John Moan (forgot his call and spelling) (SK) in San Antonio used to run a few BC-610s. He always rotated his 100TH and 250TH tubes to keep gassing from forming in them. He had about a dozen BC-610s and around 17 R-390A receivers in his shack. I think he used to say it was bad to lie them on their side too. He seemed to know what he was doing and swore the cycling of the tubes was neccessary to keep them alive. He claimed storing these tubes would kill them in time. I am only talking about 100TH and 250TH tubes. Lee w0vt Houston __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Classic Link Coupled Tuner
Hi Brian: Next time we come up there I will be sure to give you some notice. But I had already taken a side trip to Don's, K4KYV, to get rid of some stuff. I was needing to spend some time with the kids there in Searcy. If you are getting a good match and there is no heating then the energy from the XMTR must be getting to the antenna. I would worry too much about it all. But it sounds like you have the same brain disease that I have, CAN'T STAND TO NOT KNOW WHY. I must have spent weeks studying and experimenting with this matching stuff and neutralizing circuits, don't even get me started. HIHI One thing I have found is that the breadboard design is the best for changing and learning and the shot glass can be used for an insulator or to ease the frustration, which comes often for me. While on the subject, I must tell you of an experiment I did some time back (25 years ago). I put a 6AL5 tube in the top box of a Heath Cantenna and lit it up with a 6V lantern battery. Using only one diode, I connected the plate directly to the dummy load and the cathode was by passed to ground with a .01uf ceramic capacitor and then connected to the little RCA jack on the top box. Now I had a decent peak reading RF detector. I just measure the DC on the RCA jack to indicated the peak of the RF voltage (very accurate by the way, but that's another story). I took 60 ft of open wire balanced line made of #12 wire with Phenolic spacers about every foot and stretched it out across the back yard suspended by wood chairs and such. The dummy load RF detector was then attached to the far end. I had the balanced antenna tuner connected to the feed end and a SWR meter between the tuner and the XMTR. I adjusted the tuner so that running 800 watts and with the SWR meter sensit ivity all the way up it showed nothing on the reflective meter. I then took my Simpson meter out to the dummy load and measured the voltage at the output of the 6AL5 RF detector. I of course don't remember the exact voltage but let's say about 250V DC. Then I connected 100 Ft of RG8 to the dummy load and the other end to the SWR meter. The SWR meter still show flat but the RF detector meter showed less voltage, not much less but something like 240V. I thought maybe I have made a slipup somewhere so I when through all the procedures again making sure that I disconnected the battery from the 6AL5 when not measuring so as not to have the filament voltage going down in between measuring. I got the same results each time. So I was finally convinced that the losses in a good tuner are negligible and the looses of coax far exceed the losses of open wire line. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Classic Link Coupled Tuner
Brian: In a link coupled assembly the coupling actually has an effect on the Q, the effective load. But increasing the Q of a parallel tank (less coil more capacitance) will increase the coupling. Using taps on the coil for the antenna connections reduces the coupling while increasing the Q. The fewer turns there are between the antenna connections the greater the Q of the tank but less voltage is coupled to the antenna. The coupling between the link and the main tank increases because the Q of the main tank went up as it was loaded less. The voltage across the ends of the main tank will go up as the taps are moved towards the center. You can get a different run of coupling by tuning the link in parallel instead of series. But this will double the voltage across the link capacitor. You can get yet another run of different coupling factors by using a swinging link. It all boils down to this: The tuner should be adjusted so that there is no L or C reactance at the antenna terminals. Then the coupling is adjusted to pull the current from the rig so that Erf/Irf = desired Z-load (generally 50 ohms). If the Q of the circuit is not high enough you will not be able to couple enough energy out of the XMTR to draw enough RF current to get the desire E/I (LOAD resistance) low enough. If the Q is too high in the wrong place then the circulating currents in the tanks of the tuner will either have high loss or begin arcing. If it aint getin hot and it aint arcin then it's OK. There always a number of ways to do it. BTW: I was in your neck of the woods a couple of weeks ago visiting with Kids in Searcy and drove out to the Peti-Jean park. I guess we must have gone right by you place. 73 John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of WA5AM Sent: Saturday, August 15, 2009 5:06 AM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] Classic Link Coupled Tuner I'm bumfuzzled... This is not exactly AM, but I use an AM tx with it... Several years ago, I built a large link coupled tuner from parts I managed to get off ebay. A large coil with rotating link in center which came out of a vintage BC transmitter, and a large Johnson split stator variable, about 35 to 475 pF. I breadboarded these two components together and have been using it since on 75 and 40 meters with great results using 450 ohm ladder line to a doublet cut for 75 meters. After I built this, I found tapping points on the main coil that worked well on 75, ultimately giving me a standing wave of near perfect on a given freq. I did that simply by trial and error... About two years ago I purchased an inductance/capacitance meter. Never thought to measure the coil taps on the tuner with it, etc., until yesterday. I disconnected the cap, coil and feedline from one another and checked the inductance of the main coil where I had my 75 meter taps. To my surprize it was only ~7.2 uH!! For the heck of it, I measured the variable in the range it normally is adjusted to and it showed about 220pF. According to formula, my values do have a resonant value near the upper end of 75 meters, and in real life do well around 3.885Mhz with my conditions. Looking at other tuners, homebrew and commercial, it appears most will tap a balanced coil like this at about 22uH and set a capacitance at around 75 pF to get resonance on 75 meters. Since I have plenty of coil on this, I did exactly that and can not get anywhere near where I need to on my tuner. What gives?? As a reference; the lowest SWR I could achive was about 5:1, and there was a noticeable attenuation on rx too. Since I can get it to work just fine with my original 7.2uH tap, it really is no big deal to me, but I am curious why others I've seen use (and can use) a lot more inductance. I know using more C gives better 'Q', but why is my real life parameters so far from the norm, and why will it not tune using the normal parameters of L and C? There must be something not right on feedline length, or the length of the doublet itself, maybe? By the way, the measured inductance of the link coil is about 3uH. One other thing I've noticed is that many seem to indicate the variable is paralleled to the entire length of the coil, not directly to the points where it is tapped for a given band. See this diagram: http://www.possumnet.com/Graphics/Diagram.jpg I don't do this. My variable is is paralleled directly to the feedline taps. 73 Brian / wa5am __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to
Re: [AMRadio] Classic Link Coupled Tuner
Thanks Bob Just to add a little something: Someone said earlier, something to the effect, that there may be a non resonate antenna and feed line combination that can cause a lot of trouble. This is very true because then the L and C of the tuner must add or subtract reactance in order to make the whole system resonate. This is often more easily done when you have a lot of capacitance to work with. So having a high Q tank in the tuner has its advantages. John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of rbethman Sent: Saturday, August 15, 2009 12:20 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Classic Link Coupled Tuner Thank you John! __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] push pull output XFMRs and neg feedback
Hey Darrell; Some how I missed your post until just now but yes I did do the swap. John -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of WA5VGO Sent: Thursday, May 14, 2009 7:34 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] push pull output XFMRs and neg feedback Have you tried swapping the transformers to make sure it isn't something else? 73, Darrell, WA5VGO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] push pull output XFMRs and neg feedback
OK Dennis: Give yourself a pat on the back. The output XFMR is the trouble. I was able to switch them out today and confirm that the channel that was bad is now good. So does anyone have one of these critters. The output XFMRs are Thordarson 22s63 5000 ohm ptp primary -- 8 and 16 ohm secondary -- rating 40 watts Maybe a pair of substitutes. I have a little extra room on the chassis if necessary. Contact me off list please -- wa5bxo at gmail dot com John Coleman, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of John Coleman Sent: Thursday, May 21, 2009 9:18 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] push pull output XFMRs and neg feedback Jim: Open Loop: A square wave input at about 1000 HZ results in a square wave at the grids of the KT88s. Both channels appear equal in amplitude at the grids of the KT88s. But the output of the 8 ohms tap to the speakers is not a square wave but is sort of a pointed sine wave. And the good channel has a nearly twice the peak to peak voltage. As inverse feedback is added: As the inverse feedback is added, the good channel begins to flatten out into a square wave and looks pretty good with only a small amount of ring at the leading edge. However, When inverse feedback is added to the channel of question, the wave begins to flatten but goes into sustained ring at the top and bottom of the square wave. Adding just a little more FB and it breaks into oscillation. The one thing I haven't checked is switching the speakers. There may be some weird thing with the crossover networks making a resonate circuit there. It's easier than changing out the output XFMRs. I could try changing the KT88s as well. Now that would be weird!! Dennis said he thought it could be a shorted turn in the output XFMR, in spite of NOS, and it is beginning to look more and more true. I seem to always find the weird stuff. I serviced TVs for many years before going into the computer field. I have met and talked with many TV techs and not one of them has ever detected or changed out the main power supply choke in the old tube type sets. Yet I have found two in my life that were shorted. No inductance: Ripple was the same on both ends. So either the others guys just never fixed the ripple in the picture or they never saw it. John Coleman, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] push pull output XFMRs and neg feedback
Jim: Open Loop: A square wave input at about 1000 HZ results in a square wave at the grids of the KT88s. Both channels appear equal in amplitude at the grids of the KT88s. But the output of the 8 ohms tap to the speakers is not a square wave but is sort of a pointed sine wave. And the good channel has a nearly twice the peak to peak voltage. As inverse feedback is added: As the inverse feedback is added, the good channel begins to flatten out into a square wave and looks pretty good with only a small amount of ring at the leading edge. However, When inverse feedback is added to the channel of question, the wave begins to flatten but goes into sustained ring at the top and bottom of the square wave. Adding just a little more FB and it breaks into oscillation. The one thing I haven't checked is switching the speakers. There may be some weird thing with the crossover networks making a resonate circuit there. It's easier than changing out the output XFMRs. I could try changing the KT88s as well. Now that would be weird!! Dennis said he thought it could be a shorted turn in the output XFMR, in spite of NOS, and it is beginning to look more and more true. I seem to always find the weird stuff. I serviced TVs for many years before going into the computer field. I have met and talked with many TV techs and not one of them has ever detected or changed out the main power supply choke in the old tube type sets. Yet I have found two in my life that were shorted. No inductance: Ripple was the same on both ends. So either the others guys just never fixed the ripple in the picture or they never saw it. John Coleman, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Meter scale software
Maybe this is it. http://www.tonnesoftware.com/meterdownload.html Installation did not put and icon up, I had to go find the file meter.exe and run it. But it looks cool. John WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] push pull output XFMRs and neg feedback
Thanks Jim I'll give that a try before switching the XFMRs out. I guess what your saying is that the slight tolerance differences of components and layouts me be enough to cause this and that the XFMR wires are color coded different doesn't mean they or all wrong. In his schematic the resistor is 3300 ohms and the capacitor is .001 uf. The plate resistance of the 6SN7 is supposed to be about 7000 ohms. With this data, how does one calculate the roll off and how does the un-bypassed cathode resistor and feedback to that cathode effect the response. I have always done this sort of thing experimentally but I figure that someone with a degree may know the actual methods to calculate all of this. BTW the cathode resistor is 1000 ohms and the plate resistor is 47K. Thanks for the tip. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] push pull output XFMRs and neg feedback
Jim I had a chance to add the 3300 ohm resistor and the .001uf capacitor to the circuit at the grid of the phase splitter but it did not help or if it did it was negligible. The oscillation is at 8000 to 1 cps. I think I had originally said 18000 but the scope says different and it is audible even for an old smell like me. BTW I don't have any pre-emphasis or de-emphasis in the FB path it is strictly a resistive pad. I'll be running some test soon and will let you know the results. BTW the output XFMRs are Thordarson 22S63 5000 ohm ptp primary -- 8 and 16 ohm secondary -- rating 40 watts John Coleman, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Jim Candela Sent: Friday, May 15, 2009 11:06 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] push pull output XFMRs and neg feedback John, I had similar issues with a stereo 6L6 amp I built many years ago. The oscillation would come and go, and it eventually killed the tweeters on my old Utah 12 3 ways. The following article describes the problem well in a similar amplifier: http://www.pmillett.com/file_downloads/chicago_100W_amp.pdf See R1, and C1, and description on paragraph 1 on page 63. I know you are experiencing the issue in only one channel. I bet if you swap transformers, the problem stays in that same channel. Adding the R1, C1 like the article might completely eliminate the problem. Here is a more updated circuit designed by Patrick Turner. He uses a transistor current source in the phase inverter such that he gets perfect balance: http://www.turneraudio.com.au/Integrated5050.htm Patrick talks a bit about stability, and ultrasonic oscillations. A good read, as is his whole website. Regards, Jim WD5JKO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] push pull output XFMRs and neg feedback
No Darrell, I haven't swapped the XFMRs yet. That is part of the testing that will take place but it is all on hold for a few days because of Boy Scout events this week end. I'll keep you guys informed as to what is found. Come see us sometime Darrell. Bret, Yep I'm sure it is a phase problem and is probably in the XFMR. I fear they just aren't equal. But before I go to the trouble of swapping all the wires I am going to make phasing tests throughout the amplifier. It is only a few stages so it should not take long. But I can't get to it till next week. CU Later, 73 John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
[AMRadio] push pull output XFMRs and neg feedback
This is maybe a little off subject here but I ran across an interesting thing. It may be of interest for someone building higher quality speech amplifiers of modulators for AM. While constructing two identical amplifier circuits with inverse feed back for a stereo operation, I discovered that the introduction of the feedback caused oscillations in one channel, so I checked my circuits to see if I had wired some part of the push pull drivers or something in the output different from the other circuit. I had not. But reversing the output XFMR plate wires did correct the trouble for the most part. Now here is what is interesting. These are standard old fashion Thordarson push pull OTs for 6L6s. It has three wires on the primary and three on the secondary. Primary is green=P1 Red=B+ Brown=P2. Secondary is Black=ground Brown=8ohm Green=16ohm. I checked the XFMR with the ohmmeter before ever wiring it in but I did not check its through put phase. But the XFMR primary has to be wired different (that is the Green and Brown wires of the primary must be reversed) in order for the feedback to be inverted as it should be. I said this corrected the trouble for the most part but not altogether. Now here is another phenomenon. I can increase the negative feedback, on the one amp that has always worked OK, to reduce the gain a lot with no oscillations. But on the other amp where I had to reverse the wires, I can only reduce the gain a small amount before the circuit goes into a high frequency (maybe 18000HZ) oscillation that is barely audible. If I put the wires back where I thought they should go, I get about a 500HZ oscillation immediately upon introduction of any feedback. The circuit is push pull KT88 grounded cathodes, 425 V plate supply, regulated 300volt screens, RC coupled grids with separate bias pots for each grid and set to about 40ma cathode current per tube. Grid leak resistor is 100K from grid to bias circuits. Diver is a differential 6SN7 with 47K plate resistors and with a cathode balance pot. Phase splitter is also 6SN7 - first plate is direct to grid of second triode. Cathode resistor and plate resistor for splitter is 22K. Appropriate B+ decoupling between stages. The feedback point is cathode resistor of first stage. Feedback take off is from 8ohm connection of output XFMR. Appropriate decoupling and divider between take off point and feedback point. This is a very common type of circuit used in many higher quality amplifiers. This one just doesn't have the ultra linear OTs with the screen taps and cathode windings. I may need to move swap the XFMRs from one channel to the other just to test or prove if it is the output XFMR that is causing all this. But before I do I will open the feedback loop and parallel the two channels inputs. Then do a low frequency test to make sure of my wiring phase all the way through both amp. I guess I will sync the on the input then go dual trace to look at the paths in each amplifier. Then start sweeping up input frequency to see where I get phase shifting that might cause this. Has anyone else found NIB / NOS XFMRS that don't match but are supposed to. May Thordarson just never intended these to be used with feedback and I just happened to find one that works OK but not the other. John Coleman, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] push pull output XFMRs and neg feedback
That is a possibility Dennis however there is little if any difference in the open loop gain of the two circuits or their output level before clipping about (40 watts). I was thinking that perhaps the primary wires were color coded incorrectly, as I am nearly positive they are, and the secondary may be as well. As a result I may have the speakers tied to the 16ohm output and taking the feedback from there would be greatly different than the 8ohm connection. The XFMR load would be entirely different and untold other differences. I will check ringing and resonance as well though. Thanks for the input Dennis John Coleman, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Dennis Gilliam Sent: Thursday, May 14, 2009 5:48 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] push pull output XFMRs and neg feedback It sounds like you may have a shorted turn in one of them, NOS notwithstanding. It has happened to me, and it forms a tuned circuit resulting in a phase shift as it is an LC network now. 73 de W7TFO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
[AMRadio] Linear Operation for AM
As Don K4KYV and others have said before, linear amplifier's most linear operation, for AM, generally occurs when the drive carrier level is set to about 20 to 25 percent of the peak capability of the linear amplifier. Unfortunately this is also where the worst efficiency occurs. Therefore there is a lot of tube heat dissipation that occurs. This is all OK if the amp is big enough but it can cause replacement of tubes to be necessary more often than most of us would prefer. John WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] HF homebrew 100 plus watt vacuum tube Transmitter
The decision about what tubes to use is always a topic of a lot of conversation. For lower than 1000 Volt plate supplies, the multiple 6146s (I would use 3 in the RF and 4 in the modulator) is probably the best choice. Because of smaller tuning components in the tanks. Higher voltages means more spacing on everything. For higher voltages and fewer tubes the 812, 811, 805 and some others mention would be good. My favorite would be the push pull 812 class C final modulated by class B 811As running 1500 Volts or so. John WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Ralph G. Rogers Sent: Sunday, May 10, 2009 5:41 PM To: amradio@mailman.qth.net Subject: [AMRadio] HF homebrew 100 plus watt vacuum tube Transmitter Hi Folks, I am planning on building an Amateur band HF homebrew 100 plus watt vacuum tube Transmitter. What I need is advice, information and ideas. I seek to find out what reasonable priced currently being manufactured 100 plus watt transmitter tubes are available and from what source. I wish to design around the tube so I can expect to find replacements when needed. Respectfully Yours, Ralph G. Rogers, K5RGR, DCR140T, TxCAP-3866 __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Filament choke
This may be an unwarranted alarm but if it were me, I would increase the value of the RFC in the bias line from 100uh to maybe 1mh. Your resonate frequency with the .02 bypass capacitor is quite low but I suspect a substantial amount of RF current will still be passing through a 100 uh coil and there may be heating especially if the choke is a tightly wound thing on .25 in form. Good Luck John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of sbjohns...@aol.com Sent: Thursday, April 30, 2009 8:37 AM To: glowb...@piobaire.mines.uidaho.edu Cc: amradio@mailman.qth.net Subject: Re: [AMRadio] Filament choke Here's my schematic so far for the 160m amp: http://www.wd8das.net/160m-GI7B.JPG This one won't be a as pretty as some... I'm going to build it on a steel chassis that has been used by others for at least four other projects and is literally swiss-cheesed with useful holes. (more holes than steel maybe) The front panel is 1/8 aluminum sheet also somewhat holey, but smoothed and now painted nicely with textured gray. The cabinet looks like it came from a later-vintage Meissner Signal Shifter with liftable lid and plenty of ventilation holes. Steve WD8DAS sbjohns...@aol.com http://www.wd8das.net/ - Radio is your best entertainment value. - __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Google
It's Samuel Morse's birthday John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of zilas...@la.twcbc.com Sent: Monday, April 27, 2009 10:46 AM To: Discussion of AM Radio in the Amateur Service; mkh...@kias.org; Discussion of AM Radio in the Amateur Service Subject: [AMRadio] Google For you old timers (like me) who know the morse code, check out Google's main page today, www.google.com. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] old BC AM FM or TV rigs
Jim: There might have been a lot of cool parts in that FM station. For instance, I was given and old GE 10KW TV XMTR back about 30 years ago. It had a lot of stuff I did not want, but others did, and it had a whole lot of stuff that was way cool that I wanted. It had 270 degree 1ma meter movement and large precision wire wound meter multiplying resistors. It had several large plate XFMRS and chokes. It had oil capacitors. Two of the chokes were 12 Hy open frame construction which Don, K4KYV, disassemble and rebuilt into a single 40Hy modulation reactor which I am very proud to have and I use still today. There were mercury vapor rectifiers and filament XFMRS. All of these things an more (I can't name all) were used in the construction of my PP-304tL rig. And parts that I did not want went all over the South, Of course you must have an empty garage to do all this in and that is where most folks say no, as they might to building their own vehicle from scrap. I f I had it to do now I would have to say no because there is just no time or space in my life right now. Hopefully that will change before I get to old to walk. Anyway I hope someone got the old FM rig and used the parts. John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Jim WB5OXQ inb Waco, TX Sent: Saturday, April 04, 2009 11:32 AM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] 7160Kc - The Video I would love to participate in this but I have no vintage equipment right now. Except for my linear amplifier I am running Kenwood which with the heil mike and good dsp audio settings I am told I have excellent audio. My amplifier is American made TenTec Titan 425 and easily makes legal limit on am with about 10 watts of drive giving my transciever a lot of headroom. I do have a camcorder and a digital camera that can shoot video and a video capture card in my pc. I watched the video and was impressed but like most I am not fortunate to have a broadcast transmitter. I was offered one a couple of years ago from a station that went dark but it was FM so I knew I could not use it for ham. Jim WB5OXQ __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] old BC AM FM or TV rigs
Yep it was 1KW DC input to the RF final amp. That is plate V times plate current. And 100% modulation was not counted as input power. Many folks believed, including myself, that 100% modulation meant not pinching the carrier off on the scope. So we all let the positive peaks go to where they may. As a result the carrier output could be around 880 Watts of carrier and PEP could go very high. I could hit 7KW PEP output without pinching the carrier. But with the new rules 1500 Watts PEP output is the limit. The mythical 375 watt carrier limit is only true for a single sine wave modulating the carrier to 100%. A carrier 100% modulated by a single sine wave will result in a PEP of 4 time the carrier. If the carrier is 375 watts then the that would be 1500 watts. In my case the carrier limit is even less because of the lopsided characteristics of my voice. That is assuming that I send the lopsided peak positive. But if I send them negative then I can run 600-700 watts of carrier output and still stay under the 1500 watt PEP limit. The funny thing about all this is, that the audio power is the same in either case, only the polarity of the audio is different when the microphone wires are reversed. But I can turn the carrier level up by increasing the plate voltage on the class C final only. (separate power supply for the modulator). I do this until the downward going peaks on the scope no longer pinch the carrier. Afterwards, the PEP is still the same but the carrier level is much higher. As to whether this is good or bad depends on the listener and the type of detector being used. Some say no difference, some say not as loud as before or doesn't sound 100% modulated. Others say the extra carrier level helps stomp back the QRN. All I know is audio power is the same and the power in the sidebands is the same in either case. I wrote a very detailed article about all of this several years ago but can't find it right now. John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Jim WB5OXQ inb Waco, TX Sent: Saturday, April 04, 2009 12:18 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] old BC AM FM or TV rigs This was a fairly recent Continental 5KW transmitter, all solid state except for the single ceramic PA tube maybe a 4cx5000. I figured little value for ham so it was sold to another small station. It would be very difficult to get a bc rig into my shack but there could be room in the garage for one. This weekend I have to lower the crankup and repair my 40 meter dipole that fell in recent high winds. I listen most evenings on 7160 but often hear little AM. I am told when I am on I am very loud in some parts of the country. I understand that 375 watts of carrier is all that is allowed on AM. I used to think it was 1KW back in the 50s when I used to visit my ham neighbor. - Original Message - From: John Coleman j...@pctechref.com To: Discussion of AM Radio in the Amateur Service amradio@mailman.qth.net Sent: Saturday, April 04, 2009 12:02 PM Subject: Re: [AMRadio] old BC AM FM or TV rigs Jim: There might have been a lot of cool parts in that FM station. For instance, I was given and old GE 10KW TV XMTR back about 30 years ago. It had a lot of stuff I did not want, but others did, and it had a whole lot of stuff that was way cool that I wanted. It had 270 degree 1ma meter movement and large precision wire wound meter multiplying resistors. It had several large plate XFMRS and chokes. It had oil capacitors. Two of the chokes were 12 Hy open frame construction which Don, K4KYV, disassemble and rebuilt into a single 40Hy modulation reactor which I am very proud to have and I use still today. There were mercury vapor rectifiers and filament XFMRS. All of these things an more (I can't name all) were used in the construction of my PP-304tL rig. And parts that I did not want went all over the South, Of course you must have an empty garage to do all this in and that is where most folks say no, as they might to building their own vehicle from scrap. I f I had it to do now I would have to say no because there is just no time or space in my life right now. Hopefully that will change before I get to old to walk. Anyway I hope someone got the old FM rig and used the parts. John, WA5BXO Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] old rules
I found the article Jim I found the Article - turns out I never put a link to it on the web page http://www.qsl.net/wa5bxo/asyam/aam3.html John Coleman __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Broadcast transmitter rescue
If voltage is needed for the exciter a long coax line from the VFO can be tuned with a small network to provide the voltage needed at the grid of a distant buffer. John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of sbjohns...@aol.com Sent: Saturday, February 14, 2009 7:48 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] Broadcast transmitter rescue Todd wrote: Don, I'd be curious to hear your thoughts on maximum connection distance electrically for a VFO. I'm not Don but I have some thoughts: It depends a lot on the output impedance of the VFO, I'd think. If it is low-Z, say less than 100 ohms, then I'd think you could run coax quite a long way. The DDS VFO I built and use with my Gates BC-1T has a video op-amp as the output line driver so it is no problem to run a fair distance on regular coaxial cable. See http://www.wd8das.net/DDSVFO/ddsvfo.html which shows both the VFO circuit and the interface to the Gates AM rig. If you have a VFO with a high-Z output, maybe the special low-capacitance coax used for broadcast antennas on cars would help. Steve WD8DAS sbjohns...@aol.com http://www.wd8das.net/ - Radio is your best entertainment value. - __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] 833 AM rig
As I recall, the swinging Formica bar was about 3/8 inch across and had feed through solder eyelets. I'm sure it was roommy enough to allow the center lead to pass around with out much trouble. I believe that his reasoning was to allow for more room and also to reduce the capacitance change at the center of the tank coil. His belief was that this would cause an unbalance in the tank, little though it may be. Otis has never run push pull 833 RF finals, as for as I know, but for sure never in the rig since I have known him. He said I never want to be accused of running more that the 1KW input legal limit Of course the 833 could have run more than the 1KW input it would not have been significant enough to make a large difference. And most of the tubes he had were pulls that would hardly hold grid drive up for high plate current. The double RF choke for shunt coupling is a pain. I had so much trouble with hot spots on chokes that I wound a special RF choke for the purpose. It was wound on two 1.5 inch by 5 inch ceramic forms. I wound with #20 enamel wire 4 sections each, about 15 or 20 turns on each section, on each form. The two forms were mounted on a plexiglass plate supported in the middle by a cermic insulator. The tops of the coils went to the plate of the 304TLs and the common connection at the bottom went to another RF choke of high inductance but not a low capacitance choke. The other choke went to the bypass and then to the modulated high voltage. I found a real buy on some 500 pf 20KV coupling caps rates at about 7 amps of RF. These monsters were about 3.5 inch in diameter and 2.5 inches thick with a metal plate on each end and a screw hole for a 1/4-20 screw. The coupling capacitors then went to the ends of the tank circuit. The center of the tank coil had a RF choke to g round. With the coupling capacitors and the plate RF choke bypass the total capcitance as seen by the moulator was about 2000pf which is pretty high for most rigs but I ran about 1600 volts at 600 ma so the modualator load was a low Z and a little extra capacitace didn't hurt much. The 304TLs showed little color and the output was just under 800 watts. The low impedance load that the final represented to the modulator was the reason for four 813s class AB2 in the modulator instead of just two. I soon found that with good audio design in the speech amplifier and coupling that more voltage was needed to get the positive peaks up to where they would not flat top when the negative peaks wher just about the cut the carrier at 100%. After raising the modulator supply voltage to 2700 volts I was able to keep the peaks from flat topping on the scope at 3 time the carrier level. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] 833 AM rig
Otis is 87 yrs old. I'll get back with you guys later. John From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Bob Peters Sent: Monday, February 09, 2009 8:40 AM To: 'Discussion of AM Radio in the Amateur Service' Subject: Re: [AMRadio] 833 AM rig OTIS had his 85th Birthday party on Saturday... All the guys BXO/ SEE and a lot of others had for him but you are correct he is not on the air. Something like the floor in the shack is not safe... From what we hear he is doing well..You are correct on the sweet sounding rig... Very Best 73's, Bob W1PE Mesquite,TX http://www.w1pe.com From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of LEE BAHR Sent: Monday, February 09, 2009 7:59 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] 833 AM rig Otis is alive, doesn't get on the air, lives in the far reaching Northern area of Houston, Tx. John Coleman, WA5BXO sees him from time to time. Lee, w0vt - Original Message - From: Bob Carpentermailto:bcarpenter_...@bellsouth.net To: 'Discussion of AM Radio in the Amateur Service'mailto:amradio@mailman.qth.net Sent: Monday, February 09, 2009 8:03 AM Subject: Re: [AMRadio] 833 AM rig What ever happen to Otis ? I can guess that by this time is may be a SK. I use to listen to him along with W4RKG on 75 meters in the 60's running some beautiful a.m. I recall that Otis was in Shreveport La. Ma he had such a sweet a.m. sound. I would listen to him along with a large group on 75 using a Allied span master reg. receiver that I build in 65. Great memories, wish a.m. could be like that again. Bob Carpenter KB4WEC bcarpenter_...@bellsouth.netmailto:bcarpenter_...@bellsouth.net From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Jim Wilhite Sent: Sunday, February 08, 2009 4:48 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] 833 AM rig Maybe John/WA5BXO will read the messages soon. Otis/K5SWK built one like this some years back and it still plays over at De Queen, AR. Ken/KA5RHK still uses it. I would imagine John can tell us what Otis did. Jim/W5JO - Original Message - I would be interested myself. Mod-U-Lator, Mike(y) W3SLK - Original Message - Hello I like to build an AM transmitter with one tube 833A,any one have a circuit diagram... many thanks joe __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] 833 AM rig
Ok here's the deal. Otis runs a single 833 in the class C final and modulates with a pair . The single 833A is in a circuit for push pull but only has the one tube in it. and only one nuetralizing capacitor and only one coupling capacitor to the ballanced tank with swinging link. The grid circuit is a push pull tank but any other typewill work as it's only function is to supply the proper driver to the final grid. The plate tank is a push pull balance type because the phase inversion for the neutralizing cap is accomplished by the ballanced plate tank. The tank circuit is shunt fed to keep the DC and audio off of the tank circuit. The center tap of the coil does have a RF choke but it goes to ground to insure that there is no audio or DC on the tank components. He used to run about 3000 volts on the plates but after the AM power reduction thing he ran about 2500V at 200 ma. I can pretty much draw the circuit but you may wish to consult the web page at http://www.qsl.net/wa5bxo/pptriodes/pptriodes.htm Please note that the circuits do not depict the shunt feed tank coil. But I can draw that up if someone needs it. The above web page has not been proof read by anyone that is good at it, so there may be some spelling, grammer and other mistakes in it. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] TEST
tnx Tom, Ineeded a chuckle John -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Tom Chesek Sent: Wednesday, February 04, 2009 1:08 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] TEST We are not doing tests today, only quizzes to prepare for tests. - Original Message - From: John Coleman j...@pctechref.com To: Discussion of AM Radio in the Amateur Service amradio@mailman.qth.net Sent: Wednesday, February 04, 2009 2:05 PM Subject: [AMRadio] TEST I-net Provider change to an Exhange Server. Does Email to AMRadio still work? John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Mod Transformer
Don: It's so nice to see a good tech post from you. You have such way with words it is difficult for me to see how anyone would not understand. Some times I get to writing and make assumptions that folks know what I mean such as the statement about audio needing to be twice the DC. (You will notice I corrected that in a later email). I was explaining to one of the other members that the tubes do not produce the audio or RF energy. They simply control the current flow through a load. In respect, putting in a bigger switch, alone, will not make the light brighter. Wish I had more time: John, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of D. Chester Sent: Monday, January 26, 2009 11:07 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] Mod Transformer The output voltage of a modulator is determined by its plate supply voltage and the modulation XFMR turns ratio. You need to think in terms of voltage transformation. If you are using a common power supply on the final and modulators, or more exact, the modulator plate supply and the final plate supply have the same voltage, then the ratio that you use is what determines the maximum modulation. That is true irrespective of the nominal impedance of the transformer, the p-p load impedance of the modulator tubes or the modulating impedance of the final. Of course, the tubes have an optimum p-p load impedance at any given plate voltage, and a transformer has an optimum primary and secondary impedance at which it works best. But the actual transformation is based on turns ratio. The impedance ratio stamped on the nameplate of the transformer is a nominal value, and a good transformer should be able to work at up to twice the nominal value and as low as half the nominal value with little degradation in performance. The impedance transformation ratio is the square of the turns ratio. For example, a transformer with a 2:1 turns ratio has a 4:1 impedance ratio. 100% modulation occurs when the audio voltage from the modulation XFMR is 2 X the plate supply. Actually it's when the peak output voltage, the combined audio and DC voltage from the winding adds up to 2 X the plate supply voltage. The peak a.c. output voltage from the transformer is equal to 1 X the DC plate supply voltage. When it is in the same polarity as the DC voltage, the two voltages add together to produce a sum that is 2 X the plate voltage at the positive modulation peak. At the opposite peak of the audio cycle the polarity is reversed and the two voltages cancel, leaving zero volts on the plate of the final. This is the negative modulation peak. At maximum drive the modulator tubes conduction (assuming they or big enough) takes the plate voltage close to 0 Volts at the peak of the audio for that conduction cycle. Nothing you can do will take the voltage lower than zero. As one tube hits the Zero volt peak then the other tube will hit the 2 X plate voltage point. That is theoretical. In actual practice, there is nothing you can do to pull the instantaneous plate voltage below about 20% of the power supply voltage. In the case of screen grid modulators, the plate voltage can never be pulled to a lower voltage than the DC screen voltage. As one tube reaches maximum conduction, the instantaneous voltage on the plate of the other tube will reach about 1.8 X the DC plate supply voltage. Something between 2:1 and 1:1 is what is needed. You need a little extra to make up for the fact that the modulators will use some power in plate dissipation and you will want a little head room for voice lopsidedness (everything is not a perfect sine wave). Experience information from Don, K4KYV, indicates that between 1.2:1 and 1:4:1 is generally a good choice. 1.2:1 will give you more head room but will require more modulator current perhaps larger tubes. 1:4:1 will probably just be enough audio with very little head room, but will require less modulator current and lighter demand on the modulator tubes. If you chose 1.2:1 for plenty of head room then choose modulators with a little more current capability or double up (push pull parallel). Using a higher step-down ratio of 1.6:1 will just barely allow you to reach close to 100% modulation with no headroom whatever, but the modulator tubes will run more efficiently. Somewhere between 1.2 and 1.4 will allow more headroom at the expense of efficiency. But that extra headroom is needed for minimum distortion and splatter, since driving a modulator or linear amplifier (exactly the same thing except the modulator amplifies audio while the linear amplifies rf) right to the saturation point results in more distortion. But watch the modulator plate current and make sure you don't exceed the tube ratings. If so, double up to use a pushpull parallel modulator. However, this may increase the audio driver
Re: [AMRadio] Mod Transformer
Paul: Modulation XFMRs have a lot of different ratings. 1. Insulation breakdown voltage ratings. 2. Audio wattage (can be misleading as this rating is often at 1000hz and it may not hold true for 100hz). 3. Max secondary current if any. Some XFMRs assume that you will be using a modulation reactor as well. 4. Turns ratio of course. (A confusing issue to a lot of people). The output voltage of a modulator is determined by it's plate supply voltage and the modulation XFMR turns ratio. 100% modulation occurs when the audio voltage from the modulation XFMR is 2 X the plate supply. You need to think in terms of voltage transformation. If you are using a common power supply on the final and modulators, or more exact, the modulator plate supply and the final plate supply have the same voltage, then the ratio that you use is what determines the maximum modulation. At maximum drive the modulator tubes conduction (assuming they or big enough) takes the plate voltage close to 0 Volts at the peak of the audio for that conduction cycle. Nothing you can do will take the voltage lower than zero. As one tube hits the Zero volt peak then the other tube will hit the 2 X plate voltage point. The peak to peak plate voltage max is 2 X the plate supply on one modulator tube. If plate supply is about 600 volts then the modulation max is 1200V PTP. In push-pull circuits the output voltage would be 2 this or 2400 volts Peak to Peak. Since the power supply voltage is the same on the final this would be twice the amount of audio voltage required to modulate it. This is too much of an over kill on a 1:1 XFMR. Taking a step down, and using a 2:1 turns ratio XFMR and the audio drops to 1200 Volts. This is the exact amount of voltage required with no head room for error or loss in the XFMR. You will not be able to actually hit 100% and distortion will be fairly high. Something between 2:1 and 1:1 is what is needed. You need a little extra to make up for the fact that the modulators will use some power in plate dissipation and you will want a little head room for voice lopsidedness (everything is not a perfect sine wave). Experience information from Don, K4KYV, indicates that between 1.2:1 and 1:4:1 is generally a good choice. 1.2:1 will give you more head room but will require more modulator current perhaps larger tubes. 1:4:1 will probably just be enough audio with very little head room, but will require less modulator current and lighter demand on the modulator tubes. If you chose 1.2:1 for plenty of head room then choose modulators with a little more current capability or double up (push pull parallel). You may want to consider a modulation reactor even if your XFMR says it can handle the secondary current. Keeping the current out of the secondary will greatly improve the low frequency capability of the XFMR. You want regret it. This may be more info than you needed. Good Luck John Coleman, WA5BXO -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net] On Behalf Of Paul Baldock Sent: Saturday, January 24, 2009 6:36 PM To: amradio@mailman.qth.net Subject: [AMRadio] Mod Transformer Does anybody have a good reference as to how to calculate modulation transformer requirements? Thanks - Paul __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body.
Re: [AMRadio] Mod Transformer
Opps, I should have said 100% modulation occurs when the peak to peak audio voltage from the modulation XFMR secondary is twice the plate supply to the final amplifier. Not: 100% modulation occurs when the audio voltage from the modulation XFMR is 2 X the plate supply. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body.
Re: [AMRadio] Amazed any young ham made it to adulthood
I've been shocked, knocked a across the room even, more times than I care to talk about. Once I thought I was going to die and then afraid I wouldn't. Back a few years ago, I don't think people sued as much as they do now. If some accident happened we didn't try to blame it on some one else or a neglect of manufacturing. We simply took our licks for our own stupidity and mistakes. I'm not saying that manufactures shouldn't worry about the consumer but, I think they should worry more about the longevity of service to the consumer. Too many Americans, today, seem think that everything they buy should come with some type of personal protection plan. My work is servicing personal computers. A lot of our customers are John and Jane Doe types that use the PC as a home entertainment device. I tell them that entertainment on the internet often comes with spy ware or some other type of booger. I've had them say to me, Well what good is the internet, if you can't safely play poker, look at porn, steel music, etc. I wish that our customers were more corporate types like it was about 15 years ago. And I especially wish that HTML, Java, and active X had never been expanded as they are now. Of course I guess I wouldn't be nearly so busy but it sure gets tiresome dealing with these people. Why do people think that they must bee entertained? And that somebody owes it to them. I apologize for my ranting off subject. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body.
RE: [AMRadio] re:transformer info
200uf is typically not enough capacitance for proper Q on 80 mtrs (maybe not even 40 mtrs) even in and AB linear let alone class C so my guess is that it had some fixed capacitors that got switched in to circuit to add to it. John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Tuesday, November 25, 2008 12:53 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] re:transformer info Hello all. I got a deal on ebay, it looks like some sort of amp or transmitter with a built in power supply, not sure what exactly it was supposed to do, it has a socket for a 4cx250b type tube, a big loading cap, a bunch of octal sockets, rectifier tubes, driver, exciter? The power section has a transformer, grey, square, solder sealed, oil filled, marked: edo 06722 Acme T-14034 2850 volts center tapped, scratch70ma. I am trying to find out the current rating as the scratch is right on the number. it looks to big for 170 ma. The thing also has a nice round choke painted all black, no numbers, but it looks like a utc CG102, only slightly smaller. Its also got a 6uf 1500 volt oil filled cap. I was hopeing to use the transformer to build up a seperate supply for the mod deck of the 3X4d32 rig (811A's). The voltage is right, 170ma would be a little light, 270ma would be fine. A 4cx250 type tube could run at 250ma (peaks) at 2000 volts, in AB1 they rest at 90 ma and get up to 250 ma. About 200 pf in the loading cap, 160 and 80 meters, or 80 and 40 meters, there was a switch, some parts are missing I got it for $45.00 and $15.00 shipping, its got 3 filiment transformers, the HV supply, the 4cx250 type socket, some good power resistors, small adj coils, etc. The chassis was a hacked up mess, but it was wired ok for homebrew... If anyone has any info on the transformer, please let me know, i looked through old fair radio catalogs, which had most of the easy to get stuff from way back...I did not see anything like it. Brett N2DTS __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Licensing
Hey Bret, I can relate a little as I was licensed back around 63 and it was tough for me to do the 13 wpm to go from novice to general. But I finally did it about a month or two before the novice expired while I was in high school. Then while in the military and stationed at Randolph AFB they started the incentive licensing thing. Well I could take just the written test to go to advance class and that meant I could stay on 3845 where we once used to hang out. So I got permission from the NCOIC, then a work friend and I went to Houston to the federal building to test, he for his general and me for advanced. All went well and I was fat and happy for quite some time till another friend pressured me into trying for the 25 wpm code to get extra class. Well it took three tries on the 25 wpm but I made it. This was in about 1975 or 76 anyway they did not have all the digital and satellite stuff back then, thank god. So I guess there is always going to be something we don't like. For me CW was hard. I enjoyed it as a novice and have used it at field day a few times but was never very good at it. So I did my hard stuff (CW) back then now it is replaced with stuff I somewhat make a living at so I really am glad I don't have to use it or test for it to keep my license in ham radio. I better hush or they will find away to change that. 73, John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Re: 160m AM receiver project
Steve, did I miss something, where's the S meter in the circuit probably in the plate or cathode circuit of the IF. But I don't see it in the skem. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Monday, October 27, 2008 7:00 PM To: amradio@mailman.qth.net; [EMAIL PROTECTED] Subject: [AMRadio] Re: 160m AM receiver project I noticed that the schematic diagram I'd posted wasn't the latest version with all the mods, so I updated it this evening. It is at the bottom of the page... http://www.wd8das.net/160mRX/160mRX.html Steve WD8DAS [EMAIL PROTECTED] http://www.wd8das.net/ --- Radio is your best entertainment value. --- __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] ceramic tubes
Hi Brett: Yep, in spite of the fact that you see these type of tubes mostly in HF to UHF service they work very nicely as modulators. I was given 4 of the 4CX300s a long time ago and a buddy of mine and I split them up and each built modulators using a pair, with 2500 volts on the plates in class AB1 service. They worked very well into low impedance loads far below 10K ohms. In fact if the plate load Z is too high they will draw too much screen current so it is important to monitor the screen current on these tubes. I began to think that there plate current swing had no saturation point that I could reach. These 4CX300 tubes had very strange sockets. The connections were in little rings with tabs up and down the ceramic post. I wrapped small wire back and forth around each ring and twisted it tight then soldered all of the wires into a broken octal tube base. I first tested the tubes as modulators by turning each upside down into a coffee cup of water. So that the water just covered the plates. Then I turned it all on and biased the tubes to the proper plate current. I let them idle for about 5 minutes then powered down and felt of the water. It was not even up to body temperature. So I powered back on and began to modulate. Boy was I surprised at the level of current swing for the amount of drive. But when I said a big FOUR into the microphone the water foamed and boiled immediately. My hand was poised over the plate switch so there was no damage. I went to work figuring out a mounting scheme and air system and used those tubes for quite some time. But I really don't know now what ever happened to that modulator. I think it may have been trashed by my 2nd ex-XLY. I'll blame her for it anyway HIHI. John WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Friday, October 10, 2008 6:03 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Re: ceramic tube tester No, I don't think you can test for flash over other than using the tubes. I have a LOT of old hamfest specials, and pick 2 matching resting current tubes in the modulator, and they work ok for a few weekends, then flash. I pick some more matched tubes, same thing. I found 4 NEW 4x150a tubes at an old TV repair parts store (long gone now) and have been using the 1st set for about 6 years now without problems. The 4x150a tubes seem to work exactly the same as the 4cx250b tubes, they look the same, work the same. If you look in old handbooks, they list the 4x150a as a 150 watt tube, but its also in the 250 watt tube with the 7034, a later revision of the 4x150a? Anyway, if the tube looks exactly like the 4x250b, it has to have the same plate dissipation, both are forced air cooled, have the same fins, shape, size, etc. The older early 4x150 tubes looked different from the 4cx250b type tubes. Mine came in sealed green cans marked 4x150a/FAA, cost me $25.00 each. Brett N2DTS __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Infinite impedance detector vs diode, slew rate probem and plate modulated final
I agree Don: The series diode thing hit me wrong when I was 18 years old and I have seen patterns on the scope of resultant audio after over modulation and it ain't pretty. Besides the sharp change in waveform creating audio harmonics, another big problems of over modulation is ringing of the modulation circuit during the time interval of the over modulation. During this time interval there is no load for the modulator and the transformer and chokes will ring (undamped wave train caused by resonates circuits with very little load for those not familiar with the term). It seems to me that adding another filter circuit to the equation might only cause more ringing. One of the best ways to stop this is a shunt diode circuit from the final modulation point. The cathode of the diode goes to the final modulation point where it is reverse bias by the DC on the final. The anode goes to a resistor approximately equal to Ep/Ip of the final (although not critical). The other end of the resistor goes to ground. The diode stays reverse biased most of the time. But on occasional over modulation intervals, when the plate of the final goes to negative voltage on audio negative peaks, the diode will conduct and the audio load is switched from the RF final to the resistor that is in series with the diode. The modulation circuit is never without a load. The diode of course, most be rated at more than 2 times the final supply voltage. If it is a tube rectifier, high vacuum types are best rather than mercury vapor or gas because the later has a threshold of turn on voltage. There are a number of SS HV diodes available that have extremely high PIV and low forward drop. A meter or LED detection circuit can be added to show over modulation. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Infinite impedance detector vs diode, slew rate probem and plate modulated final
I agree Don: The series diode thing hit me wrong when I was 18 years old and I have seen patterns on the scope of resultant audio after over modulation and it ain't pretty. Besides the sharp change in waveform creating audio harmonics, another big problems of over modulation is ringing of the modulation circuit during the time interval of the over modulation. During this time interval there is no load for the modulator and the transformer and chokes will ring (undamped wave train caused by resonates circuits with very little load for those not familiar with the term). It seems to me that adding another filter circuit to the equation might only cause more ringing. One of the best ways to stop this is a shunt diode circuit from the final modulation point. The cathode of the diode goes to the final modulation point where it is reverse bias by the DC on the final. The anode goes to a resistor approximately equal to Ep/Ip of the final (although not critical). The other end of the resistor goes to ground. The diode stays reverse biased most of the time. But on occasional over modulation intervals, when the plate of the final goes to negative voltage on audio negative peaks, the diode will conduct and the audio load is switched from the RF final to the resistor that is in series with the diode. The modulation circuit is never without a load. The diode of course, most be rated at more than 2 times the final supply voltage. If it is a tube rectifier, high vacuum types are best rather than mercury vapor or gas because the later has a threshold of turn on voltage. There are a number of SS HV diodes available that have extremely high PIV and low forward drop. A meter or LED detection circuit can be added to show over modulation. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] infinite impedance detector vs diode
The way I understand it, The infinite impedance detector is a device such as a tube or FET that normally draws output current unless reversed biased. The device is reversed biased to cutoff and then input signal turns it on like class B service but the input does not draw current. The output is taken from the cathode, or source in the case of a FET, in follower fashion. I am not sure how this is going to correct the slew distortion that is caused by the RF filtering and discharge rate of the output. Perhaps it is because of the follower effect of having a low Z output with no diode at the output. This may mean that the discharge is at the same rate as the charge? I'd be interested to see what you come up with Jim. There are several circuits on the internet (Google infinite impedance detector). I have never played with this. John Coleman, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Tonne Sent: Wednesday, September 03, 2008 7:56 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Diode demodulator appnote Agreed. Send me a schematic of such and I will see if I can run it through the analysis routines. - Jim Tonne WB6BLD TonneSoftware.com __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] infinite impedance detector vs diode
Very interesting Jim: It seems to me from a designer / builder standpoint that the relatively high Z input, of the infinite impedance detector, would or could increase the Q of the last IF XFMR thereby affording a sharper band pass if that was desirable? Of course we're still talking envelope detection here. Is it possible to analyze a synchronized - product demodulator such as the Sony IC or the old MC1496 circuits? The MC1496 is just the mod/demod chip and requires an external synchronized BFO. So for your circuit test, you could use the same carrier that you generate the AM signal with, as input to the MC1496. The BFO carrier insertion must be phased locked to the AM signal input to be detected. See http://www.onsemi.com/pub_link/Collateral/MC1496-D.PDF I built one of these detectors once. It was a somewhat discrete design using a 455KC OSC with a varactor diode in the circuit. The OSC was fed to buffer and then a RC phase separator where a 90 degree signal (Q) was fed to a MC1496 and the other phase (I) was fed to the second MC1496. The output of the (Q)MC1496 was filtered and fed to the varactor diode to synchronize the OSC with the IF signal which was fed to both of the MC1496 inputs paralleled . The (I)MC1496 output was where the audio was taken off. If the station being tuned in had any phase modulation of 60HZ on the harrier, as a lot of the BC610s had due to cabinet vibration, then the 60HZ audio would be heard very well. I can remember one station that could turn his modulator off and I could still detect his voice when he yelled into the rig. HIHI The new SONY chips, I think, have it all built in except for tuned circuits. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] infinite impedance detector vs diode
Very interesting Jim: It seems to me from a designer / builder standpoint that the relatively high Z input, of the infinite impedance detector, would or could increase the Q of the last IF XFMR thereby affording a sharper band pass if that was desirable? Of course we're still talking envelope detection here. Is it possible to analyze a synchronized - product demodulator such as the Sony IC or the old MC1496 circuits? The MC1496 is just the mod/demod chip and requires an external synchronized BFO. So for your circuit test, you could use the same carrier that you generate the AM signal with, as input to the MC1496. The BFO carrier insertion must be phased locked to the AM signal input to be detected. See http://www.onsemi.com/pub_link/Collateral/MC1496-D.PDF I built one of these detectors once. It was a somewhat discrete design using a 455KC OSC with a varactor diode in the circuit. The OSC was fed to buffer and then a RC phase separator where a 90 degree signal (Q) was fed to a MC1496 and the other phase (I) was fed to the second MC1496. The output of the (Q)MC1496 was filtered and fed to the varactor diode to synchronize the OSC with the IF signal which was fed to both of the MC1496 inputs paralleled . The (I)MC1496 output was where the audio was taken off. If the station being tuned in had any phase modulation of 60HZ on the harrier, as a lot of the BC610s had due to cabinet vibration, then the 60HZ audio would be heard very well. I can remember one station that could turn his modulator off and I could still detect his voice when he yelled into the rig. HIHI The new SONY chips, I think, have it all built in except for tuned circuits. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Tonne Sent: Thursday, September 04, 2008 3:52 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] infinite impedance detector vs diode I have just finished updating the diode demodulator writeup to include, right at the end, a quick examination of one of the Infinite Impedance detectors I found on the 'net. I used the one by Rohde, knowing that it was from a reputable fellow and so would work right off the bat. Which it did. Interesting circuit but for linear operation I will stick with a forward-biased diode demodulator. Spose I should post that too. - Jin Tonne WB6BLD TonneSoftware.com __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] infinite impedance detector vs diode
Yes I know what you mean about wheels turning, I should not be doing this but it interests me so. I never learned how to use the spice software and some day I have to do it. Yes the Hi Z detector would be an advantage I would think but I have heard others say it makes the bandpass to narrow. Go figure! 73, and tnx fer all the info John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Tonne Sent: Thursday, September 04, 2008 7:18 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] infinite impedance detector vs diode John: I am under the impression that the high input impedance of that AM demodulator is perhaps its most important point. The fact that it seems to buffer the output load from the detection action seems nice to me. I think it could be made temperature-stable rather easily by adding a diode in series with that 6200 ohm resistor from the base to ground. Then change the resistor. Base idles about .67 volts above ground so as to just barely turn on the transistor. Oh yes - the URL for those that may have missed it: http://tonnesoftware.com/appnotes/demodulator/diodedemod.html Yes, it would be possible to do the same kind of look-see on a product detector. All it takes is time! I have some other stuff that needs attention right now; wheels are squeaking. - Jim Tonne WB6BLD TonneSoftware.com __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Diode demodulator appnote
That is an interesting article Jim. And it was a very good explanation about the distortion and its reason. I'm not 100% sure yet but I think there may be a mistake on the last two monitor examples. The schematics seem to be the same. I will need to look them over better when I get home this evening. I'm sure there are deficiencies in any demodulation system. It would be interesting to see the comparisons to others systems such as the infinite impedance detector or the synchronous balanced product demodulators (supposedly one of the best). One thing I know, that it is not forgiving when it comes to an AM signal with a small amount of 60HZ phase or frequency modulation. But that is really a XMTR problem. I bet a guy could write a book about demodulation systems comparisons. I love this stuff but got to get to work now. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Tonne Sent: Tuesday, September 02, 2008 7:56 AM To: AM Amateur radio group Subject: [AMRadio] Diode demodulator appnote Gents: I was doing some maintenance on my website and ran across an appnote that will probably be of interest to the group. It discusses the diode demodulator as used in most AM receivers. Lotsa pictures, no math, hopefully clear explanations of that demodulator from different viewpoints. You can see it here: http://tonnesoftware.com/appnotes/demodulator/diodedemod.html Have fun! Hope it proves of interest. - Jim Tonne Tonne Software __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] ribbon cable
Thanks to all who replied and your suggestions were all good ones. These are short pieces anywhere from 1 ft to 4 ft in length so I think I will put some aside and dispose of the rest, connectors and all. Thanks again. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] ribbon cable
I have several boxes of ribbon cable assortment. Some pulls from used computers, some new that came with motherboard and were not needed. Floppy drive cables, IDE cables 40 wire and 80 wire, SCSI cables, ETC. I have too many and will never use them in my computer business besides I get more every day along with power cables. So, aside from separating the wires for use as small hookup wire for projects or making loop antennas what else or they good for. Anybody need some or want to make an offer for them. They may all go to the trash soon. Make suggestions for use here but if you want some call me. Call for more details. LAND LINE 281 367 6765 John Coleman __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] 1500 KHz trap for NC-156, one more time...
Just a little tidbit of an interesting story, at least for me, HIHI On a similar incident of BC interference: Back when I was about 18 yrs old, I was experiencing AM radio interferences from two stations at the same time. Now this was a long time ago so some of the details here may be incorrect such as the exact stations involved. As I remember we had two radio stations that were very strong 740 and 790. These two stations could be heard simultaneously every 50 KC across the 80 meter band. The RCVR at the time was a S85. When I tuned the stations in on the BC band they did not appear to be so strong as to over load the front end of the RCVR nor did adjusting the RF gain or antenna tune have any effect. I went up on the roof with a portable SW RCVR and as soon as I got near a guy wire there was the trouble. It turned out that the two stations were mixing together in rusty connections of the guy wires and when I had put the telescopic pole on top of the house and tied the last guy wire down I just dropped the leftover 15 feet of guy wire down over the gable and let it spiral down the edge of the house. Once I picked up the left over guy wire the problem disappeared. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] An interesting story about BC interference
Just a little tidbit of an interesting story, at least for me, HIHI On a similar incident of BC interference: Back when I was about 18 yrs old, I was experiencing AM radio interferences from two stations at the same time. Now this was a long time ago so some of the details here may be incorrect such as the exact stations involved. As I remember we had two radio stations that were very strong 740 and 790. These two stations could be heard simultaneously every 50 KC across the 80 meter band. The RCVR at the time was a S85. When I tuned the stations in on the BC band they did not appear to be so strong as to over load the front end of the RCVR nor did adjusting the RF gain or antenna tune have any effect. I went up on the roof with a portable SW RCVR and as soon as I got near a guy wire there was the trouble. It turned out that the two stations were mixing together in rusty connections of the guy wires and when I had put the telescopic pole on top of the house and tied the last guy wire down I just dropped the leftover 15 feet of guy wire down over the gable and let it spiral down the edge of the house. Once I picked up the left over guy wire the problem disappeared. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] 1500 KHz trap for NC-156
Good work Larry: I have just a quick suggestion and it may not be even noticeable. When tuning for the 1500KC null on the trap start tuning from the low end (maximum capacitance) stop tuning when you get enough attenuation even if it is not centered on 1500KC. You may find that you can reach enough attenuation of the unwanted 1500KC when the trap is actually resonating at a much lower frequency. This will bring the gain back up a little on the 160 meter band. It may not work but it won't take long to find out. 73, John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Larry Szendrei Sent: Monday, August 11, 2008 12:54 PM To: Jim Tonne; Discussion of AM Radio in the Amateur Service; Glowbugs Subject: Re: [AMRadio] 1500 KHz trap for NC-156 Hi Jim, Apologies if my post was confusing. Yes, I'm attempting to reject 1500 KHz, which is the IF frequency. The receiver covers 0.3 - 1.2 MHz, and 1.7 - 17 MHz, skipping a band approximately centered about the IF frequency. Therefore, the ideal (and impossible) filter would be a brick wall stopband from 1.2 - 1.7 MHz, with zero attenuation outside of that range. I mentioned 80M only to comment that I noticed no attenuation that far removed from the filter center frequency. Yes, I wanted minimal attenuation at 160M as well. There were no signals on that band when I was playing with this last night around 7PM local time to use for reference, which is why I didn't quote attenuation for 160M. However I was hearing plenty of static crashes on 160M with and without the filter. I imagine the attenuation on 160M will be somewhat similar to what I saw at 1.13 MHZ, roughly 12 dB - nothing to write home about, and hardly optimized, but good enough considering the time and effort I care to invest in this particular project. 73/TNX, -Larry/NE1S - Original Message - From: Jim Tonne [EMAIL PROTECTED] Sent: Mon, August 11, 2008 13:33 Subject:Re: [AMRadio] 1500 KHz trap for NC-156 Larry: Let me jump in on that trap thing for just a moment. You are trying to reject what frequency / frequencies? And you want to pass what frequency / frequencies? Reading your last mail here leaves me confused as to what you wanted to do. I thought you wanted to reject 1500 or so and still pass 160 meter band but you just now mentioned 1100 and the 80 meter band. - JimT - End of original message - __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] 1500 KHz trap for NC-156
Hi Larry You are correct in the thinking of a higher Q (more C less L) however it is very important the lower L factor be made of larger wire with proper spacing (a high Q type coil). There are special dimensions and wire spacing to be considered for a high Q coil assemblies. I won't go into that here as there are probably more expert coil winders available here on the list than I am. But I do know that it makes a difference. The whole thing will need to be put in a shielded box else coil assembly may act as an antenna for the 1500KHZ As I recall, 100pf and 100uh resonates at around 1590KC but you may want higher C yet? Another thing to consider: You might use an antenna tuner but not the pi-net type with the series coil as these are low pass circuits. Instead the seldom seen pi-net with two coils to ground and a series capacitor making a hi-pass network would be real good but doing two adjustable coils would be a pain. So the old fashioned link coupled parallel tank is best for this application. Perhaps some of the modern T nets might be good also I don't know. Perhaps the trap and a tuner together would work well. Good Luck John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Larry Szendrei Sent: Friday, August 08, 2008 7:09 PM To: Glowbugs; AM Reflector Subject: [AMRadio] 1500 KHz trap for NC-156 Hello all, I'm working on putting an AM station together for a friend, consisting of a Viking II and NC-156, both quite cosmetically-challenged, but complete. I did a bunch of work to bring them back to operation, including significant audio improvements in the Viking. However, the IF in the NC-156 is 1500 KHz, and as you might expect there is bleed-through of broadcast stations on or near that frequency, especially on the 160M band, and especially at night, when there is sky-wave propagation there. The undesired signals are so strong that it makes operation on 160M totally impossible. I first tried a series-resonant circuit from ANT to GND, and it was totally ineffective, probably because the source impedance of the antenna is low. Then I reconfigured my L and C as a parallel resonant circuit in series with the ANT at the receiver, and I was able to totally eliminate the 1500 KHz +/- interference. But, 160M signals are highly attenuated also (although S/N, if you will, where N is the the 1500 KHz interference, is much better). Also WBZ on 1.3 MHz is very noticibly attenuated. My trap consists of a 140pf air trimmer at ~40% mesh (= ~56 pF) in parallel with 200µH. I'm thinking a higher Q circuit (more C and less L) will sharpen the peak and I'll have less attenuation 300 KHz away from the resonant frequency of the trap. Or is there a better way to eliminate the 1500 KHz QRM? 73 es Tnx, -Larry/NE1S __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] 1500 KHz trap for NC-156
Hi Larry You are correct in the thinking of a higher Q (more C less L) however it is very important the lower L factor be made of larger wire with proper spacing (a high Q type coil). There are special dimensions and wire spacing to be considered for a high Q coil assemblies. I won't go into that here as there are probably more expert coil winders available here on the list than I am. But I do know that it makes a difference. The whole thing will need to be put in a shielded box else coil assembly may act as an antenna for the 1500KHZ As I recall, 100pf and 100uh resonates at around 1590KC but you may want higher C yet? Another thing to consider: You might use an antenna tuner but not the pi-net type with the series coil as these are low pass circuits. Instead the seldom seen pi-net with two coils to ground and a series capacitor making a hi-pass network would be real good but doing two adjustable coils would be a pain. So the old fashioned link coupled parallel tank is best for this application. Perhaps some of the modern T nets might be good also I don't know. Perhaps the trap and a tuner together would work well. Good Luck John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Larry Szendrei Sent: Friday, August 08, 2008 7:09 PM To: Glowbugs; AM Reflector Subject: [AMRadio] 1500 KHz trap for NC-156 However, the IF in the NC-156 is 1500 KHz, and as you might expect there is bleed-through of broadcast stations on or near that frequency, especially on the 160M band, and especially at night, when there is sky-wave propagation there. The undesired signals are so strong that it makes operation on 160M totally impossible. I first tried a series-resonant circuit from ANT to GND, and it was totally ineffective, probably because the source impedance of the antenna is low. Then I reconfigured my L and C as a parallel resonant circuit in series with the ANT at the receiver, and I was able to totally eliminate the 1500 KHz +/- interference. But, 160M signals are highly attenuated also (although S/N, if you will, where N is the the 1500 KHz interference, is much better). Also WBZ on 1.3 MHz is very noticibly attenuated. My trap consists of a 140pf air trimmer at ~40% mesh (= ~56 pF) in parallel with 200µH. I'm thinking a higher Q circuit (more C and less L) will sharpen the peak and I'll have less attenuation 300 KHz away from the resonant frequency of the trap. Or is there a better way to eliminate the 1500 KHz QRM? 73 es Tnx, -Larry/NE1S __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Old Firestone radio
I am fixing an old radio for a friend of mine. It is a Firestone Air Chief S-7398-8 Picture found on the internet here http://radioattic.com/item_sold.php?radio=0002474X Replaced the 5Y3 rectifier and repaired the speaker. Believe it or not, the flexible wire from the cone connection of the voice coil was open. Only the string was left in the middle. I was able to tack a piece of solder wick to the top side of the voice coil wire and made a small hole in the cone then soldered the other end to the frame terminal. I then glued the small hole on the cone. I was afraid that something in the output XFMR or the hum bucker in the magnet assemble would be shorted that would have caused this but all check OK. The radio appears to be working now but there is a 4 pin connector on the chassis which I have determined to be for an antenna coil assembly connection. I believe there is supposed to be some type of wave magnet wound on the missing back. It is probably a multi tap or multi winding assembly with 4 wires that plug into the radio chassis. I do not know the specifications on this assembly as to whether it is part of some resonated RF circuit or just a loop or a few loops. Any info on the antenna coil assembles or schematic would be appreciated. Maybe I can manufacture something. TNX, 73, John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Old Firestone radio
Thanks Bill I really appreciate the help. You may be right but it appears to me that the two loops are part of the RF front end and are resonated on two bands. Looks like I may need to do some experimenting unless someone has one and wants to count the turns for me HIHI. 73, John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bill Ramsey Sent: Friday, August 01, 2008 5:31 PM To: 'Discussion of AM Radio in the Amateur Service' Subject: RE: [AMRadio] Old Firestone radio Hi John, Take a look at the schematic that is found here: http://www.nostalgiaair.org/PagesByModel/312/M0006312.pdf It looks like it was just two loop antennas on the back cover. But, the schematic does show that there is a connection for an external antenna that can be used instead. Antique Electronic Supply has a couple of replacement loop styles that might work if you have the room on the back. Bill KA8WTK -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John Coleman Sent: Friday, August 01, 2008 5:43 PM To: 'Discussion of AM Radio in the Amateur Service' Subject: [AMRadio] Old Firestone radio I am fixing an old radio for a friend of mine. It is a Firestone Air Chief S-7398-8 Picture found on the internet here http://radioattic.com/item_sold.php?radio=0002474X Replaced the 5Y3 rectifier and repaired the speaker. Believe it or not, the flexible wire from the cone connection of the voice coil was open. Only the string was left in the middle. I was able to tack a piece of solder wick to the top side of the voice coil wire and made a small hole in the cone then soldered the other end to the frame terminal. I then glued the small hole on the cone. I was afraid that something in the output XFMR or the hum bucker in the magnet assemble would be shorted that would have caused this but all check OK. The radio appears to be working now but there is a 4 pin connector on the chassis which I have determined to be for an antenna coil assembly connection. I believe there is supposed to be some type of wave magnet wound on the missing back. It is probably a multi tap or multi winding assembly with 4 wires that plug into the radio chassis. I do not know the specifications on this assembly as to whether it is part of some resonated RF circuit or just a loop or a few loops. Any info on the antenna coil assembles or schematic would be appreciated. Maybe I can manufacture something. TNX, 73, John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Old Firestone radio
Thanks Bill I really appreciate the help. You may be right but it appears to me that the two loops are part of the RF front end and are resonated on two bands. Looks like I may need to do some experimenting unless someone has one and wants to count the turns for me HIHI. 73, John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bill Ramsey Sent: Friday, August 01, 2008 5:31 PM To: 'Discussion of AM Radio in the Amateur Service' Subject: RE: [AMRadio] Old Firestone radio Hi John, Take a look at the schematic that is found here: http://www.nostalgiaair.org/PagesByModel/312/M0006312.pdf It looks like it was just two loop antennas on the back cover. But, the schematic does show that there is a connection for an external antenna that can be used instead. Antique Electronic Supply has a couple of replacement loop styles that might work if you have the room on the back. Bill KA8WTK -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John Coleman Sent: Friday, August 01, 2008 5:43 PM To: 'Discussion of AM Radio in the Amateur Service' Subject: [AMRadio] Old Firestone radio I am fixing an old radio for a friend of mine. It is a Firestone Air Chief S-7398-8 Picture found on the internet here http://radioattic.com/item_sold.php?radio=0002474X Replaced the 5Y3 rectifier and repaired the speaker. Believe it or not, the flexible wire from the cone connection of the voice coil was open. Only the string was left in the middle. I was able to tack a piece of solder wick to the top side of the voice coil wire and made a small hole in the cone then soldered the other end to the frame terminal. I then glued the small hole on the cone. I was afraid that something in the output XFMR or the hum bucker in the magnet assemble would be shorted that would have caused this but all check OK. The radio appears to be working now but there is a 4 pin connector on the chassis which I have determined to be for an antenna coil assembly connection. I believe there is supposed to be some type of wave magnet wound on the missing back. It is probably a multi tap or multi winding assembly with 4 wires that plug into the radio chassis. I do not know the specifications on this assembly as to whether it is part of some resonated RF circuit or just a loop or a few loops. Any info on the antenna coil assembles or schematic would be appreciated. Maybe I can manufacture something. TNX, 73, John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Resistors
The interesting thing here is that in a half watt resistor of 500,000 mega ohms, the current must be less that 1 micro amps and that would be at a voltage of 500,000 volts. That resistor would need to be longer than a couple of inches to prevent it for arcing around the outside and as someone said in a glass vacuum chamber. So curiosity has me. Maybe I missed it, but what is its intended use. If for a high voltage meter for measuring static charge, I bet a 0-1 micro amp movement will cost more than your gasoline bill. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Well, it has finally happened!
Wait till ya see my new #47 lamps I'm gonna make a fortune with them. Gold plated support stems will produce less thermal noise you know! Ooopps I hope I didn't let the cat out of the bag!! John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of James M. Walker Sent: Monday, June 16, 2008 7:09 AM To: amradio@mailman.qth.net Subject: [AMRadio] Well, it has finally happened! The Audio Phools have finally reached the Epitome of silliness. found at : web page www dot usa dot denon dot com/productdetails/3429.asp I think I am definitely in the wrong business! Jim WB2FCN __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Well, it has finally happened!
Wait till ya see my new #47 lamps I'm gonna make a fortune with them. Gold plated support stems will produce less thermal noise you know! Ooopps I hope I didn't let the cat out of the bag!! John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of James M. Walker Sent: Monday, June 16, 2008 7:09 AM To: amradio@mailman.qth.net Subject: [AMRadio] Well, it has finally happened! The Audio Phools have finally reached the Epitome of silliness. found at : web page www dot usa dot denon dot com/productdetails/3429.asp I think I am definitely in the wrong business! Jim WB2FCN __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Dummy Load
Hi Rick: Some time ago I located 12 - 600 ohm 100 watt or more non inductive resistors. I purchased them from http://www.goldmine-elec.com/. They are a surplus dealer. My plan was to build a dummy load by paralleling all of them in an air vented box but I never got to it. Some day I will. In the mean time that is what I recommend for you to look for. These are long (maybe 10 - 12) snap-in resistors about 1 diameter made of carborundum or something like that, with silvered ends for snapping into large 1 sockets on standoffs. Good Luck John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rick Brashear Sent: Thursday, May 15, 2008 1:35 PM To: 'Discussion of AM Radio in the Amateur Service' Subject: [AMRadio] Dummy Load I know this has been beaten to death many times, but for the sake of an old man with a bad memory could we discuss the most economical (very important) way to provide a dummy load for testing a broadcast transmitter. I have a few Cantennas, but they get hot real quick at 1000 watts and I'd like something I could be a little more confident in. If I were to use the proper number of series/parallel non-inductive resistors at say 100 watts each, what kind of support system would be best to insure at least a one minute key down time? Would immersing them in oil or attaching them to heat dissipating metal with a blower be the better choice? Thanks for any and all advice you may offer.. Rick/K5IAR __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Gas and mecury rectifiers
Don, I don't know why but this has stuck a curiosity point in me. Do you know anything about the pressure in these tubes? I'm sure the mercury vapor rectifier tubes are supposed to be vacated of air, but what is the mercury vapor pressure and what is the difference in pressure from cold to hot. I wonder if it is just a result of a vacuum leak that causes some type of corrosion on the anode. Also I wonder what the gas pressure is in the 3B28 type gas rectifiers and what the density of the gas is. Maybe it is possible that in the gas rectifiers the gas may actually seal or push the atmosphere away from any leak. In any case I bet that if mercury tubes where heated from day one on, that they would have many more hours of good operation. Science fiction? Maybe the reason they need several days for heat up and then slow anode voltage increase is to force air out that has accumulated over years of setting cold. This might not be possible in a vacuum rectifier but in a mercury rectifier it might be that the mercury vapor pressure might displace enough of the air forcing it back out 5the hole it came in enough to allow it to work or perhaps the lengthy time is just causing a more homogenous mix of the vapor and atmospheric gasses. Science fiction? John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Sprague Capacitors
Holly Moses - I used to cut them dang things out and throw them away with out even checking them back when I was servicing TVs and other home entertainment stuff. I'm very surprised at the push pull 211s (I'm assuming that they are push pull) because most of these guys really like even harmonic distortion and don't want it canceled. John, WA5BXO Bob said: Ok. You think a $21K amp is something? Check this out... http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItemrd=1item=260230806640ssPageN ame=STRK:MEWA:ITih=016 __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Anonymous QST Author suggests that Part 97 requires 6 kHzAM Bandwidth Limit
I just don't get it. It has been many years since I have seen a crowded band but who knows what the next sun spot cycle may bring! Beside's Don, I have checked your bandwidth many times and found you to be very close to the so called desired width of +/- 3300 Hz. I can't say with any accuracy of course, but I have twisted the knob on the XTAL filter to a narrow width, not very comfortable with CW even, and found your shots to be very few and far between and weak out beyond 3.5KHZ. Not that they are not occasionally there but another signal similar to yours could easily be copied with a carrier just 5KHZ higher or lower than yours just by using the phasing control a little. What is it that makes certain folks so hateful? Let's talk about hate. I hate those head lights with the extended blue range. One glance at one of those and I see spots. What have I got to do get a windshield with a high end filter that rolls off the blues? I think there could be a song in there somewhere. Them Headlights That Gime da Blues John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of D. Chester Sent: Thursday, April 17, 2008 1:22 PM To: amradio@mailman.qth.net Subject: [AMRadio] Anonymous QST Author suggests that Part 97 requires 6 kHzAM Bandwidth Limit On p. 64 of the May issue, the anonymous writer of the monthly Q-A Workbench column in QST entitled The Doctor is In, responds to a report by the coordinator of the ARRL OO program regarding wide AM signals with bandwidths of up to 30 kHz on 75 m. He briefly explains the relationship between signal bandwidth and the frequency response of the audio that modulates SSB and AM transmitters, then states that Bell Labs concluded many years ago that high quality voice transmission (toll quality in telco terminology) can be carried over a 300-3300 Hz frequency response, but that This worked better for the grey-haired Bell scientists who were likely to have lost some of their high frequency hearing. He goes on to allege that an AM signal occupies a bit more spectrum than two SSB signals, based on the notion that there is no need to transmit audio frequency components of the voice that fall below 300 Hz, and that the usual approach with SSB is to transmit frequencies from 300 to 2700 Hz. He then cites §97.307 of the FCC rules that states No amateur station transmission shall occupy more bandwidth than necessary for the information rate and emission type being transmitted, in accordance with good amateur practice. Since voice is what is being transmitted, he suggests that the rules require AM to occupy a bandwidth of no more than about 6 kHz. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Anonymous QST Author suggests that Part 97 requires 6 kHzAM Bandwidth Limit
I just don't get it. It has been many years since I have seen a crowded band but who knows what the next sun spot cycle may bring! Beside's Don, I have checked your bandwidth many times and found you to be very close to the so called desired width of +/- 3300 Hz. I can't say with any accuracy of course, but I have twisted the knob on the XTAL filter to a narrow width, not very comfortable with CW even, and found your shots to be very few and far between and weak out beyond 3.5KHZ. Not that they are not occasionally there but another signal similar to yours could easily be copied with a carrier just 5KHZ higher or lower than yours just by using the phasing control a little. What is it that makes certain folks so hateful? Let's talk about hate. I hate those head lights with the extended blue range. One glance at one of those and I see spots. What have I got to do, get a windshield with a high end filter that rolls off the blues? I think there could be a song in there somewhere. Dem Headlites Dat Gime Da Blues John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of D. Chester Sent: Thursday, April 17, 2008 1:22 PM To: amradio@mailman.qth.net Subject: [AMRadio] Anonymous QST Author suggests that Part 97 requires 6 kHzAM Bandwidth Limit On p. 64 of the May issue, the anonymous writer of the monthly Q-A Workbench column in QST entitled The Doctor is In, responds to a report by the coordinator of the ARRL OO program regarding wide AM signals with bandwidths of up to 30 kHz on 75 m. He briefly explains the relationship between signal bandwidth and the frequency response of the audio that modulates SSB and AM transmitters, then states that Bell Labs concluded many years ago that high quality voice transmission (toll quality in telco terminology) can be carried over a 300-3300 Hz frequency response, but that This worked better for the grey-haired Bell scientists who were likely to have lost some of their high frequency hearing. He goes on to allege that an AM signal occupies a bit more spectrum than two SSB signals, based on the notion that there is no need to transmit audio frequency components of the voice that fall below 300 Hz, and that the usual approach with SSB is to transmit frequencies from 300 to 2700 Hz. He then cites §97.307 of the FCC rules that states No amateur station transmission shall occupy more bandwidth than necessary for the information rate and emission type being transmitted, in accordance with good amateur practice. Since voice is what is being transmitted, he suggests that the rules require AM to occupy a bandwidth of no more than about 6 kHz. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Re: capacitors for tank circuits
Yep, very good points Don. What I was mostly trying to say to Barrie was that tubes should be chosen first so as to acquire a ratio of plate current to plate voltage that will be used and then design the tank circuit around that. 400 Watts DC input can be achieved by 8 - 6146s in push pull parallel but because of the low voltage and high current the tank circuit would have a much larger amount of capacitance and less coil than a tank that is for a pair of 75ths at high voltage and less current. Also Barrie, when using the charts, you should be sure to choose the one for class C not the chart for linear operation. The tank Q is all together different. I used the example of the 8 - 6146s only as an example. If you were to try that you would have a difficult time finding a modulation XFMR to match the 900 ohm load that those tubes would represent to a modulator. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of D. Chester Sent: Wednesday, April 16, 2008 11:42 AM To: amradio@mailman.qth.net Subject: [AMRadio] Re: capacitors for tank circuits From: John Coleman [EMAIL PROTECTED] The size of the spilt stator capacitor that you are looking for (will) need to be determined by the voltage and current that you intend to run, The ratio of I:E determines the capacitance There are charts in the handbooks for this purpose. Be sure to consider that you are doing push pull with a balanced tank circuit as the required capacitance is only a quarter of that required for non-balanced. The voltage will determine the needed spacing of the plates. If you raise the tank capacitor above the chassis on insulators and connect the rotor to B+ you can get by with less spacing but you will need to use and insulated coupler to the knob shaft and be sure the knob shaft is grounded for safety. You can also accomplished the same thing by using two large RF chokes, one per tube, and capacitive coupling the RF to the tank circuit as is done in most PI net circuits. This way the plate tank cap can be mounted to chassis and the RF choke at the center of the tank coil can be grounded. The idea is to not have a DC + modulation voltage across the plates of the tank capacitor but just RF voltage. Capacitive coupling, as was just described, is a neat way to do this but it requires the very large long RF chokes and good coupling capacitors. For a balanced tank circuit, the capacitance is one fourth, but the voltage rating must be double that of single-ended. The reason for this is, that for a single-ended final, the tube is working into only half the balanced tank circuit, but the coil acts as a step-up autotransformer and the induced voltage across the other half of the coil is approximately equal to the voltage on the half that the tube works into, giving an rf voltage end-to-end that is twice that which is actually generated by the tube. It is exactly the same in the case of push-pull, since in class-C or even class-B service, only one tube is working into the tank circuit at a time, and each tube is working into one half of the tank circuit. Or you could think of it as each tube generating equal rf voltage, but the outputs of the two tubes are in series as they work into the tank circuit. But a capacitor with twice the voltage rating and one fourth the capacitance is equivalent to taking the original single-ended capacitor, splitting it in half, and wiring each of those halves in series. That is exactly what we mean by a split-stator capacitor. For example, take the BC-610, which runs the final at 2000 volts @ 250 mills. The tank capacitor is split stator with 150 pf per section. If the final were changed to unbalanced output, for example by substituting a 4-250 for the 250TH and converting to a pi-network, or by changing the grid tank to balanced and running the plate tank unbalanced, the final tank capacitor would need to be 300 pf in order to keep the tank circuit Q the same. That could easily be accomplished by wiring the two sections of the 150/150 split stator capacitor in parallel. The parallel connection gives 300 pf at approximately 7 kv rating. The series connection as used in the balanced tank, renders 75 pf at 14 kv rating. A single ended capacitor rated 75 pf @ 14 kv would be about the same size as the dual 150 @ 7 kv, and when new, the cost would have been about the same. The point is, for a given power level and plate voltage/plate current ratio, the physical size and cost of the tank capacitor is approximately the same, whether the tank is balanced or unbalanced. If a split stator capacitor is used, it can easily be connected up as a balanced or unbalanced tank. Of course, the number of turns in the balanced tank will be double that of the single ended one, since 4 times the inductance is required to maintain resonance at the same frequency.OTOH, the wire size in the unbalanced
RE: [AMRadio] Re: capacitors for tank circuits
Sorry if this is doubled - I think I sent it with the wrong SMTP the first time so here it goes again. Yep, very good points Don. What I was mostly trying to say to Barrie was that tubes should be chosen first so as to acquire a ratio of plate current to plate voltage that will be used and then design the tank circuit around that. 400 Watts DC input can be achieved by 8 - 6146s in push pull parallel but because of the low voltage and high current the tank circuit would have a much larger amount of capacitance and less coil than a tank that is for a pair of 75ths at high voltage and less current. Also Barrie, when using the charts, you should be sure to choose the one for class C not the chart for linear operation. The tank Q is all together different. I used the example of the 8 - 6146s only as an example. If you were to try that you would have a difficult time finding a modulation XFMR to match the 900 ohm load that those tubes would represent to a modulator. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of D. Chester Sent: Wednesday, April 16, 2008 11:42 AM To: amradio@mailman.qth.net Subject: [AMRadio] Re: capacitors for tank circuits From: John Coleman [EMAIL PROTECTED] The size of the spilt stator capacitor that you are looking for (will) need to be determined by the voltage and current that you intend to run, The ratio of I:E determines the capacitance There are charts in the handbooks for this purpose. Be sure to consider that you are doing push pull with a balanced tank circuit as the required capacitance is only a quarter of that required for non-balanced. The voltage will determine the needed spacing of the plates. If you raise the tank capacitor above the chassis on insulators and connect the rotor to B+ you can get by with less spacing but you will need to use and insulated coupler to the knob shaft and be sure the knob shaft is grounded for safety. You can also accomplished the same thing by using two large RF chokes, one per tube, and capacitive coupling the RF to the tank circuit as is done in most PI net circuits. This way the plate tank cap can be mounted to chassis and the RF choke at the center of the tank coil can be grounded. The idea is to not have a DC + modulation voltage across the plates of the tank capacitor but just RF voltage. Capacitive coupling, as was just described, is a neat way to do this but it requires the very large long RF chokes and good coupling capacitors. For a balanced tank circuit, the capacitance is one fourth, but the voltage rating must be double that of single-ended. The reason for this is, that for a single-ended final, the tube is working into only half the balanced tank circuit, but the coil acts as a step-up autotransformer and the induced voltage across the other half of the coil is approximately equal to the voltage on the half that the tube works into, giving an rf voltage end-to-end that is twice that which is actually generated by the tube. It is exactly the same in the case of push-pull, since in class-C or even class-B service, only one tube is working into the tank circuit at a time, and each tube is working into one half of the tank circuit. Or you could think of it as each tube generating equal rf voltage, but the outputs of the two tubes are in series as they work into the tank circuit. But a capacitor with twice the voltage rating and one fourth the capacitance is equivalent to taking the original single-ended capacitor, splitting it in half, and wiring each of those halves in series. That is exactly what we mean by a split-stator capacitor. For example, take the BC-610, which runs the final at 2000 volts @ 250 mills. The tank capacitor is split stator with 150 pf per section. If the final were changed to unbalanced output, for example by substituting a 4-250 for the 250TH and converting to a pi-network, or by changing the grid tank to balanced and running the plate tank unbalanced, the final tank capacitor would need to be 300 pf in order to keep the tank circuit Q the same. That could easily be accomplished by wiring the two sections of the 150/150 split stator capacitor in parallel. The parallel connection gives 300 pf at approximately 7 kv rating. The series connection as used in the balanced tank, renders 75 pf at 14 kv rating. A single ended capacitor rated 75 pf @ 14 kv would be about the same size as the dual 150 @ 7 kv, and when new, the cost would have been about the same. The point is, for a given power level and plate voltage/plate current ratio, the physical size and cost of the tank capacitor is approximately the same, whether the tank is balanced or unbalanced. If a split stator capacitor is used, it can easily be connected up as a balanced or unbalanced tank. Of course, the number of turns in the balanced tank will be double that of the single ended one, since 4 times the inductance
[AMRadio] capacitors for tank circuits
Berrie: The size of the spilt stator capacitor that you are looking for may need to be determined by the voltage and current that you intend to run, The ratio of I:E determines the capacitance There are charts in the handbooks for this purpose. Be sure to consider that you are doing push pull with a balanced tank circuit as the required capacitance is only a quarter of that required for non-balanced. The voltage will determine the needed spacing of the plates. If you raise the tank capacitor above the chassis on insulators and connect the rotor to B+ you can get by with less spacing but you will need to use and insulated coupler to the knob shaft and be sure the knob shaft is grounded for safety. You can also accomplished the same thing by using two large RF chokes, one per tube, and capacitive coupling the RF to the tank circuit as is done in most PI net circuits. This way the plate tank cap can be mounted to chassis and the RF choke at the center of the tank coil can be grounded. The idea is to not have a DC + modulation voltage across the plates of the tank capacitor but just RF voltage. Capacitive coupling, as was just described, is a neat way to do this but it requires the very large long RF chokes and good coupling capacitors. I would suggest looking for 812s for the final and modulate with 811As. I think the 811A is good to 1500 Volts at Zero bias for modulators but can run 2000 if a regulated bias supply is used. The 812s, for a push pull final, are easy to drive and easy to light up. If you're skeptical of their size then use 4 of them. The nice thing about a single band rig, is that you can just wind your coils and bolt or solder them into place. Making a adjustable output link may get creative though. Good Luck John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Parsllel capacitors for C1
I'm assuming by the large value that C1 is the output or loading capacitor of a Pi tank but I'm curious as to why the fixed capacitor are in circuit all of the time regardless of the frequency band. That part doesn't computer with me. Maybe it doesn't cover all the HF bands? Adding an extra capacitance to the output of a Pi circuit will lower the value of minimum impedance that the circuit will load to for a single frequency and coil setting. But since it is a fixed amount of capacitance then the highest load impedance that it will load into is lower than before. For instance if it was designed for 40 to 700 ohms load then it may now be 35 to 625 ohms. These numbers are not real, just representative and the scenario is for a single frequency. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John King Sent: Friday, April 04, 2008 1:37 PM To: amradio@mailman.qth.net Subject: [AMRadio] Parsllel capacitors for C1 Need a little technical consultation, if you can run this through your head for me. I have an AMP Supply LK 500ZA amplifier using two 3-500Z tubes. The tank circuit was designed and built very rinky dink and light weight. Otherwise, it is a fairly well built amp. I have had to rebuild the tank circuit and put a heavy duty band switch in it. The amp had a C1 in it comprised of a 250PF variable paralleled by two fixed 200PF caps that stayed in the circuit all the time. My question is since I don't have two two 200PF caps, would one 500PF @ 20,000KV doorknob do the job? With this change, I will have 750PF instead of 650PF at C1. Something in the back of my mind tells me that one can run into trouble when paralleling variable caps and fixed caps because it changes the minimum capacity available from the variable cap. What are your thoughts on this based upon your knowledge and experience? I can provide you with a schematic of the tank circuit directly as I have scanned that part of the tank circuit. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Fw: determining frequency of a transmitter?
Hi Mike: Probably 10 mtrs maybe 6 meters, but you need a grid dip osc meter. The grid dip osc is the exact test equipment needed for that job. But you can use one of those antenna analyzer devices also. Put two or three turns of wire about 2 inches diam on the end of some coax and hook it up to one of those antenna analyzer things that has the osc built into it and shows a readout on ohms of impedance as well as SWR. Bring the link near the tank coil in question and when you dial close to the frequency of the tank's resonance it will absorb energy and the Z meter will show a deep dip. John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mike Duke, K5XU Sent: Monday, March 17, 2008 4:39 PM To: Discussion of AM Radio Subject: [AMRadio] Fw: determining frequency of a transmitter? The output tank has some rather small tuning capacitors and a air wound coil about an inch in diameter and maybe eight turns at about half inch spacing with a tap a couple turns from one end. Any ideas? Thanks __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Resistive load on interstage audio transformers
I think you have done the right thing in your case Don because the low Z source that you have will dampen the XFMR anyway and I am sure it has a very high coupling coefficiency so that any resistive load, primary or secondary, will dampen the resonance. I wonder if you have ever though of cross neutralizing the audio circuitry since it is all PP-triodes and transformer coupled? John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Resistive load on interstage audio transformers in tubetype amplifiers
Hi Don: I have never read any info regarding this but my experience has been that there is a little better frequency response when a class A grid XFMR is loaded slighted with a resistor but not necessarily the stated Z that the manufacturer may say in specifications. I generally end up with a much higher resistance than that indicated by the Z ratio. I believe the idea is to prevent ringing and de-resonate the XFMR slightly. The load resistor will reduce the Q of the XFMR coil circuit. Series resistors from the secondary to the control grids also provide a de-resonating effect as well. This is especially true if the tubes being driven are triodes. There will be certain amount of 90 degree feed back from the plate of the tube being driven back to its control grid where the driver XFMR may resonate with it. This is the same reason that we use neutralization circuits on RF amplifiers. There were even HIFI amplifiers designed in the past using all XFMR coupling in push pull circuits and cross neutralization capacitors where used to neutralize the effects of the above mentioned feed back and peaked frequency response. Consider however that the primary of the XFMR is connected to a device producing the current change, which will have a back loading effect of its own. In tube circuitry this would be the plate resistance of the tube. Not to be confused with the recommended load impedance. In triode drivers (12AU7 for example) plate resistance is typically much lower than with pentode drivers (6AU6 for example). The triode will have less gain as a rule but it will create back load for the XFMR to help prevent resonate peaks and ringing. The pentode can do the same thing with a little proper inverse feed back but again, this will lower the gain. But be careful not to build an oscillator accidentally. John, WA5BXO PS: I had sent this earlier but with the wrong account so I apologize if come through twice. I am experimenting with GMAIL 73 __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Testing a modulator
Hey Rick Put a 300 ohm resistor in series with the bottom leg of you parallel resistors then probe across the 300 ohm there will be about 1/10 the voltage therefore safer for you and the scope. 100 Watts into 3000 ohms would mean about 547 volts RMS (about 1320 volts peak to peak) across the whole load but only about 54 volts RMS (132 volts peak to peak) across the 300 ohm. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of RICHARD GEORGE Sent: Wednesday, February 27, 2008 10:03 PM To: amlist Subject: [AMRadio] Testing a modulator How does one test a modulator. I will soon have a modulator capable of around 100 watts of audio. I know that I do not want to run the secondary of the transformer unloaded. Would it be OK to make dummy load out of a bunch of parallel connected 3 watt resistors, say about 60 watts worth at the dc resistance I will be looking at (3000 ohms). I know that this would only be good for short tests using my O scope and audio gen. Any better ways. I ran a lot of VHF AM back in the day, but only at 5 - 10 watt levels. K6KWQ Dick Amps by MORE POWER __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Testing a modulator
I might add Rick that what ever the voltage that you are running on the DC of the RF circuit the modulator must be capable of more than twice that amount peak to peak on the scope for 100 percent modulation. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rick Sent: Wednesday, February 27, 2008 10:16 PM To: 'Discussion of AM Radio in the Amateur Service' Subject: RE: [AMRadio] Testing a modulator If you can come close with an audio output transformer just put that and a speaker on it. You'll be able to hear your audio and see it on the scope as well. Rick/K5IAR How does one test a modulator. I will soon have a modulator capable of around 100 watts of audio K6KWQ Dick Amps by MORE POWER __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] TH vs TL
I ran 304TLs in push-pull class C awhile back. Required a lot of drive Just about all the 32V3 could due. I ran 500V of Grid Leak Bias at about 160 ma of grid current for the pair. At 1KW DC input using 1700Volts on the plates I got a little over 800 Watts out to the dummy load. I used 304THs for awhile in the circuit because of the much reduced drive requirements got a little less output, and a little more color on the plates but it modulated the same with good symmetry. Those are the only applications where I have compared the TL and TH. John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of W2INR Sent: Saturday, February 23, 2008 3:16 PM To: [EMAIL PROTECTED]; Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] TH vs TL Make that bias voltages, from the specs it looks like the drive will be similar in Class C W2INR wrote: The only differences will be drive and bias voltages. The performance will be the same once dialed in. G Brett Gazdzinski wrote: I don't think you will see any difference at all. I used both as modulators, with the same results, and use 811 and 812 triodes in the push pull rig with the same results also. Theoretically, the higher bias tubes work better in class C but you cant hear or see any difference. Brett N2DTS - Original Message - From: Barrie Smith [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Saturday, February 23, 2008 1:41 PM Subject: [AMRadio] TH vs TL I'm curious as to the difference in RF performance between the TH (as in 250TH) and the TL (as in 250TL) versions of older triode tubes. Looking through the Eimac spec sheets for various old, glass triodes, the only real difference appears to be that the TL versions require higher grid bias in class C RF service. I've used the TH versions of several of the older tubes a good number of times over a many year period, but I've only used the TL types in modulator service. However, if there is no real difference in RF performance between the two in class C, I'm tempted to. 73, Barrie, W7ALW __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] T3 Mod iron specs - Audio limitations, harmonics, etc.
Brian, you can extend the frequency range with external equalization to some extent. This is some what dependent on the overall slope and depths of the roll off in the original circuitry. It always results in phase shifts of the audio where a normal harmonic in a persons voice get shifted so as to change the shape of the output wave form. This shape change can make a difference in the requirement of peak power from the transmitter that it may not be able to do with out reducing overall power. On the other hand it could change the shape in such a way as to reduce the peak demand on the XMTR giving the XMTR more head room so you might be able to put out a little more average power than before. But be assured that there will be a phase shift in the lower frequencies fundamentals with respect to the harmonics in the male voice causing the peak demand to change one way or the other. If the extending of the frequency is too great in the low frequency end and not enough in the high frequency end then intelligibility will be lost on weak signals during demanding circumstances. One must of course watch out for over drive of a pre amp stage while trying to extend its roll off. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of A.R.S. - WA5AM Sent: Wednesday, February 20, 2008 5:02 PM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] T3 Mod iron specs - Audio limitations, harmonics, etc. Anyone know the approximate designed frequency range for a T-368 modulation transformer? Also, if there is a website out there somewhere that has stock audio specs on the popular commercial and military transmitters, I would be interested in seeing it. I think I know the answer to this, however I know there are a lot of you out there that have a lot more knowledge than I do on the specifics... Let's say your transmitter is limited for 200 to 3000 cycles in the audio section, either by coupling caps, cathode bypass, cathode resistors, plate loading, and any transformers... what is the result of using an external EQ and audio chain that pumps audio from the mic that is beyond either end of the audio range the transmitter is allowed by design to pass? I think this is a common mistake that a lot of us make that can cause some serious harmonics and other artifacts. I'd like to see a discussion on this if any of you experts would care to chime in ;) 73 Brian / wa5am -- Money is only temporary, radios are forever - Jim Little aka the old dawg/K5BAI __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Modulation power required
Perfectly and beautifully said Gary, except for one thing and some may not have caught it. I make this sort of mistake all the time so I'm glad I'm not the only one, HIHI. I hope you don't mind my adding in a little here just for clearing up a little detail. Original paragraph said: Well, PEP is defined as the AVERAGE power over at least one audio envelope cycle. So we need to use the average power of the carrier at least. Average power is derived from RMS voltage so we use the RMS voltage of the carrier. The above statement is defining the average power over one audio cycle would be the 2 sidebands power plus the carrier power as you said before. For PEP it should read: Well, PEP is defined as the AVERAGE power over at least one RF cycle at the most powerful point of the envelope. I have been asked this so many times so I feel compelled to expand on it. While looking at a envelope display on the scope and picking a place on the screen where the envelope is at the tallest peak then expand your scope horizontally to a mile wide display so as to see one or two RF wave forms at the place where the envelope peak was and measure the average power of the one or two RF waves at that point. Since we can't expand the scope to a mile wide display we must calculate the values as Gary said and imagine what we might see. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Modulation power required
Yes of course BOB, I was just making the statement about looking at 1 RF wave on a 1 mile wide scope to jog the imagination about what we are really defining with the term PEP. Measuring it was not intended. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bob Macklin Sent: Thursday, February 14, 2008 4:19 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Modulation power required Why not just calibrate a Trapezoid display for MAXIMUM PEP? The just watch the trapezoid display? Watching a single cycle on a scope is a difficult thing to do. HOW DO YOU AVERAGE PEP ON A SINGLE CYCLE? Bob Macklin K5MYJ Seattle, Wa, Real Radios Glow in the Dark - Original Message - From: John Coleman [EMAIL PROTECTED] To: [EMAIL PROTECTED]; 'Discussion of AM Radio in the Amateur Service' amradio@mailman.qth.net Sent: Thursday, February 14, 2008 1:55 PM Subject: RE: [AMRadio] Modulation power required Perfectly and beautifully said Gary, except for one thing and some may not have caught it. I make this sort of mistake all the time so I'm glad I'm not the only one, HIHI. I hope you don't mind my adding in a little here just for clearing up a little detail. Original paragraph said: Well, PEP is defined as the AVERAGE power over at least one audio envelope cycle. So we need to use the average power of the carrier at least. Average power is derived from RMS voltage so we use the RMS voltage of the carrier. The above statement is defining the average power over one audio cycle would be the 2 sidebands power plus the carrier power as you said before. For PEP it should read: Well, PEP is defined as the AVERAGE power over at least one RF cycle at the most powerful point of the envelope. I have been asked this so many times so I feel compelled to expand on it. While looking at a envelope display on the scope and picking a place on the screen where the envelope is at the tallest peak then expand your scope horizontally to a mile wide display so as to see one or two RF wave forms at the place where the envelope peak was and measure the average power of the one or two RF waves at that point. Since we can't expand the scope to a mile wide display we must calculate the values as Gary said and imagine what we might see. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Modulation power required
Bob: As you pointed out earlier it is nearly impossible to measure a single cycle. It is just a definition. When looking at the trap pattern or an envelope pattern one can get a pretty fair measurement of the peak voltage of the envelope. There is even meters that will give you the peak RF of an envelope or just the peak RF of the carrier. Then you can make the assumption that the single RF cycle which exits at that most extreme point of the envelope has the peak voltage of the envelope. Calculate the RMS value of that carrier voltage before putting the value in the power formula. Power can only be calculated from RMS values of RF voltage or current. (.707 Ep = Erms) Ep is the peak RF voltage at the extremes of the RF sine wave with respect to 0V center line. Erms squared / 50 ohms of the dummy load = PEP for that envelope With out modulation the carrier power is calculated the same way. Measure the peak voltage of the RF Multiply by .707 Square the product Divide by 50 BTW if your using a scope to measure the RF voltage the peak will be 1/2 the peak to peak of the RF on the scope. Also I have a circuit using a 6AL5 which can be mounted in a small chassis and affixed to the top of a Can-tenna which will allow measurement of the peak RF voltage with very good accuracy. If you interested. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bob Macklin Sent: Thursday, February 14, 2008 5:33 PM To: [EMAIL PROTECTED]; Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Modulation power required E squared / R will give average power. So how do you do that on a single cycle? Bob Macklin K5MYJ Seattle, Wa, Real Radios Glow in the Dark - Original Message - From: Gary Schafer [EMAIL PROTECTED] To: 'Discussion of AM Radio in the Amateur Service' amradio@mailman.qth.net Sent: Thursday, February 14, 2008 3:13 PM Subject: RE: [AMRadio] Modulation power required -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Bob Macklin Sent: Thursday, February 14, 2008 5:19 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Modulation power required Why not just calibrate a Trapezoid display for MAXIMUM PEP? The just watch the trapezoid display? Watching a single cycle on a scope is a difficult thing to do. HOW DO YOU AVERAGE PEP ON A SINGLE CYCLE? E squared / R will give average power. 73 Gary K4FMX __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Using a Ranger as a driver
You are confusing the Z that the Final sees with the Z that the modulator sees. The RF final is looking into a load reflected by the tank circuit Typically: the Z that a class C final sees for its RF load is (Ep/Ip)*2 This Z is used in determining the proper reactance for the tuned circuit so they will have the proper Q OTOH, the modulator is looking at a load that is determined directly by The RF stage ratio of Ep/IP. For some reason most people look at modulator power as a determination of modulation percentage and this is some what misleading. It is really easier to just say that the peak audio voltage delivered by the modulator must equal or exceed the DC voltage on the final RF amp for 100% modulation. If the DC voltage is 600V on the RF class C final then the modulator must be capable of at least 600V peak or 1200 Volts peak to peak, because for 100 percent modulation the DC on the final must vary down to 0 Volts and up to twice the DC value. If a XMTR is unloaded to draw less plate current (Ip) the plate voltage will remain at the same voltage. If there is less current being pulled by the final but the voltage is the same then the Z seen by the modulator is higher than before. The higher resistance that the audio is looking into makes it easier to produce the needed voltage. It is easier for the one modulator (the same mod XFMR ratio) to modulate a 60 watt rig with 600V than a 100 watt rig with 600 Volts. Matching the impedance is not necessary. It is often confused with the statement that says when the load Z equals the source Z there will be maximum power transfer. This is a true statement. But power transfer is not the issue here. Getting the voltage on the final to swing from 0 to 2*DC with out distortion, that is the issue. Of course we won't to do that at a power level determined by our needs. The concern was how to reduce the power from a particular rig. Is unloading the final tank all that is necessary? Perhaps it is. But there are concerns about this. Because it will make the rig easier to modulate and over modulation can occur if not monitored. This occurs because the modulator is not working into as heavy a load as before and the audio voltage at the output will rise as the load resistance goes up. Here is why. The modulator can be looked upon as a source of voltage with a certain amount of internal resistance. Voltage Source (modulator fixed input with no load) = 900Volts peak Internal resistance is a virtual value not equal to any one thing but a result of the circuit design and tubes. Internal resistance = 2000 OHMS Load resistance (EP/IP of the RF final) = 4000 ohms Total resitance is 6000 ohms The internal resistance will drop the voltage at the load to (4000/6000 * 900)= 600V peak With out changing the audio input level let's raise the load resistance to 8000 ohms (equivalent to reducing plate current to 50 percent by unloading the rig). Total resistance = 1 ohms Voltage at he load (8000/1 * 900) = 720 volts peak This increase in modulator audio output voltage is a result of unloading the rig. The audio level at the input will need to be reduced to keep from over modulating. BTW if the load is reduce to 2000 ohms (equal to the internal resistance) Total resistance = 4000 ohms Load voltage = 450 V peak 1/2 the capability of the max output voltage Maximum power is transferred at a lower voltage output but a greater current would be drawn by the modulators and probably a lot of distortion. SEE http://www.qsl.net/wa5bxo/power.html Hope this clears some things up. John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Wilhite Sent: Tuesday, February 12, 2008 9:00 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] RE: Using a Ranger as a driver Ok John, I have but a few observations and questions that might steer everyone through this. I am having trouble understanding how the Z the modulator see is greater if the plate load impedance goes down. If the Plate Z is = to the Ep divide by 2 times the Ip and you change one value how does the Z remain the same. Even if you maintain the same ratio doesn't the plate Z change as a result? In your example you change both at the same ration which maintains the same impedance. Ep 600 Ip200 ma. Zp= 600 divided by 2 times .2 = 600/.4 = 1500 Ep300 Ip100 ma. Zp = 300 divided by 2 times .1 = 300/.2 = 1500 __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Using a Ranger as a driver
As for a sweet spot on the loading of a rig I have never seen that. But I have always had 2-3 time the audio capability of what was needed. I believe in running a rig loaded to much less than the total audio that I have available. One thing that is for sure, there is a sweet spot for loading on tetrode/pentode finals because of the screen voltage on the RF final and how it gets modulation. This sweet spot has all to do with distortion where the RF output needs to follow the modulation voltage as it is applied to the final plate and screen. This is best seen on trapezoid pattern display. Adjust the screen voltage and screen modulation percentage with respect to the plate modulation percentage while looking for straight edges on the trap pattern. On tetrode finals it is best to reduce the plate and screen voltage together but it is really very seldom necessary. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Using a Ranger as a driver
I'm sure Gary know that the PTP requirement is 2 EP - he is just using references. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Geoff/W5OMR Sent: Wednesday, February 13, 2008 11:35 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] RE: Using a Ranger as a driver Gary Schafer wrote: While it is true that for 100% modulation the modulation voltage must be equal to the final plate voltage. No. Not equal to, but *twice* as much. 2*Ep But it is also misleading to say that it is strictly a function of modulation voltage. What other voltage is present at the plate (other than the DC supply voltage) if not for the AC voltage achieved by the modulator? High-level plate-modulation, we're talking about. The modulation transformer secondary works into a certain load impedance (resistance) supplied by the final plate circuit of the RF stage. While it is true that the modulation voltage must match the final plate voltage (for 100% modulation), 2*Ep. -- Driving your AM Rig without a scope, is like driving your car at night, without headlights. (K4KYV) -- 73 = Best Regards, -Geoff/W5OMR __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Using a Ranger as a driver
Yes more than voltage is required; current from the modulator is also required. The amount of current depends on the EP/IP ratio of the final. So as the final is loaded heavier for more IP then the modulator will be required to produce more current as well as the previously required voltage for 100% modulation. If the RF Final is tuned for less current the Modulator will also reduce its audio current output while the audio voltage rises. But the current will reduce faster than the voltage increases so that the modulation power is actually less even though the rig may now be over modulated. This can be proven by setting the modulation to about 50% with a tone, then make note of the modulator current of the class B modulators. Now while the rig is modulating, putting power into a dummy load, reduce Ip of the final by re-tuning a little till the current is about 50%. Note the modulation percentage level on the scope has increased and the class B modulators are drawing less current. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Wednesday, February 13, 2008 11:20 AM To: 'Discussion of AM Radio in the Amateur Service' Subject: RE: [AMRadio] RE: Using a Ranger as a driver While it is true that for 100% modulation the modulation voltage must be equal to the final plate voltage. But it is also misleading to say that it is strictly a function of modulation voltage. If it were only voltage needed then we could use a very high step up ratio modulation transformer to accomplish modulation. The modulation transformer secondary works into a certain load impedance (resistance) supplied by the final plate circuit of the RF stage. While it is true that the modulation voltage must match the final plate voltage (for 100% modulation), it must also supply current to that load impedance in order to be able to produce that voltage. Voltage times that current equals power required of the modulator. After all, all of the side band power of the modulated signal comes from the modulator. If we have a transmitter that is not 100% modulated by a certain amount of audio power and we decrease the power of the RF stage the modulation power will remain the same but the modulation percentage will increase. By increasing the load impedance of the RF stage (by reducing its plate current) the modulation transformer can produce more modulation voltage because it is working into a higher load impedance. But if we don't turn down the modulation level the modulator will still produce the same amount of power that it did before. The difference is the voltage out will be higher and the current lower. This is assuming that the final is still not being over modulated. If we go too far at letting the modulation voltage rise on the RF stage by further reduction of the RF stage plate current we will run out of plate swing room on the modulator tubes. The impedance rise on the RF stage is reflected back to modulator tubes. When that happens clipping will occur in the modulator plates. At this point we would need to change the modulation transformer ratio so that the modulator tubes see a lower impedance to keep them operating within their plate current range. 73 Gary K4FMX OTOH, the modulator is looking at a load that is determined directly by The RF stage ratio of Ep/IP. For some reason most people look at modulator power as a determination of modulation percentage and this is some what misleading. It is really easier to just say that the peak audio voltage delivered by the modulator must equal or exceed the DC voltage on the final RF amp for 100% modulation. If the DC voltage is 600V on the RF class C final then the modulator must be capable of at least 600V peak or 1200 Volts peak to peak, because for 100 percent modulation the DC on the final must vary down to 0 Volts and up to twice the DC value. If a XMTR is unloaded to draw less plate current (Ip) the plate voltage will remain at the same voltage. If there is less current being pulled by the final but the voltage is the same then the Z seen by the modulator is higher than before. The higher resistance that the audio is looking into makes it easier to produce the needed voltage. It is easier for the one modulator (the same mod XFMR ratio) to modulate a 60 watt rig with 600V than a 100 watt rig with 600 Volts. Matching the impedance is not necessary. It is often confused with the statement that says when the load Z equals the source Z there will be maximum power transfer. This is a true statement. But power transfer is not the issue here. Getting the voltage on the final to swing from 0 to 2*DC with out distortion, that is the issue. Of course we won't to do that at a power level determined by our needs. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives:
RE: [AMRadio] RE: Using a Ranger as a driver
Hi Jim, What I said was, or tried to say, when a Class C rig is unloaded so as to draw less current, that is, to tune the loading and plate circuit so that the plate dip is lower current than it was when it is tune up for max. The plate voltage will stay about the same but the plate current is less and you have less RF output as well of course. In this scenario the ratio of Ep / Ip is greater. The Z that the modulator sees is greater. Now if the plate voltage is lowered with out retuning anything, the plate current will fall as the plate voltage falls and the ratio of the two remains the same. Basically when a class C rig is set and not retuned, the Ep:Ip ratio is set and the plate current should follow the plate voltage up and down linearly. The RF should follow the plate voltage up and down as well. Some tubes and circuits need a little help with this. Such as using grid leak resistance instead of a fixed supply if the stage is to be modulated. The grid leak resistance will allow the grid voltage to fluctuate a little with the audio as the plate current goes up and down. This actually helps to keep the ration of IP to EP constant. The grid leak resistor is something of a self regulator for the ratio. The screen grid tubes have a whole other set of things that can be done to help the plate current to plate voltage ratio remain constant. There was a discussion awhile back about the plate voltage to plate current ratios. Some one was saying that a circuit will lose efficiency if the plate voltage is reduced. This is only true if the person changes the loading or tuning. What they probably meant was that if you reduce the voltage and try to retune to get the same power out that you would have less efficiency. The only thing that should happen when plate voltage is reduced is that the power input goes down and the RF power also goes down. If a rig with a plate supply of 600V is putting out 100 watts into 50 ohms the RF voltage would be 70.7 volts RMA. When the plate voltage is reduced to 300V the rig should put out 25 watts with RF voltage of 35.35 RMS on the load. Here is a chart. 600V EP 200ma IP DC input power = 120 watts RF output 100 watts Plate dissipation = 20 watts EFF = 83 percent EP/IP = 3000 ohms modulator load Z Now let's go down to 300 volts on the plate 300V EP 100ma IP DC input power = 30 watts RF output 25 watts Plate dissipation = 5 watts EFF = 83 percent EP/IP = 3000 ohms modulator load Z -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Wilhite Sent: Tuesday, February 12, 2008 11:36 AM To: amradio@mailman.qth.net Subject: [AMRadio] RE: Using a Ranger as a driver I forgot to mention John, you might explain how a Class C final sees higher impedance when the plate voltage is lowered. As I recall Zp is = Ep/(2X) Ip. So a Ranger with 600 V. on the plate with 120 ma. is seeing ~ 2500 ohms. With 300 volts at the same current, it should be seeing ~1250. Zp. Maybe this will help some of these people and you are much more eloquent than I. Jim/W5JO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Ranger driving SB220
Hi Jim, Yes, if you change the loading so as to draw less current in the final then the modulation circuit will see higher impedance. In this case, the change to a higher Z load for the modulator is not a bad thing. Audio out put stages will generally produce cleaner audio when they don't need to work so hard at delivering the current. It is easier for them to get the modulation audio voltage necessary for 100 percent modulation when the impedance they see is higher and less current is on demand. OTOH, lowering the voltage to the final (only the final) with out changing the loading will reduce current and voltage so that the load resistance that the modulator sees is the same as before. But less modulation voltage will be required to hit 100 percent of the new DC voltage. The thing to watch on tetrode finals is the screen current. As you reduce the loading on the plate the screen current will rise. This is not to bad (although worth looking in to) if the screen gets its DC and modulation from the plate supply point, but if there is a separate screen supply then you will need to adjust it down to prevent excessive screen current. All in all, the best way to reduce power for a driver /linear combo is to reduce the plate / screen supply voltage for the driver final only, via a dropping resistor or a separate power supply for that tube only. There are other considerations about reducing the load on a final, as the RF voltage at the plate of the tube will increase and may cause arcing of the plate tuning cap or some other component. It is also easy for the modulator to over modulate because it doesn't need to deliver as much current. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Wilhite Sent: Tuesday, February 12, 2008 8:16 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Ranger driving SB220 I see this discussion every so often and wonder something. If you lower the plate voltage or current the final (s) draw, what is happening to the impedance the modulation transformer sees? The design of a class C final looks at the plate load impedance of the final. If you alter that, the modulation transformer sees another impedance and may not work properly. Some instruction manuals point this out in them. The manual for my Globe Champ says to load to 320 ma. plate current @ 1kv. In another paragraph it says to load the plate current to no less than 275 ma. for the reason specified, plate load impedance. So it seems to me that one would want to load a driver to the proper output designed into the rig. If you need less driving power then dissipate with the attenuator like Johnson built or build an exciter for the power level you need. Another approach I have seen is to feed the transmitter into a dummy load with a T connector and use the other T output to go the an amplifier input. The HT 32/37/44 are low power and can be used easily to drive an amp. They only give about 25 watts out which is about right for most amps. The bad thing about sloppy modulation from an exciter is that a Class A, AB or B amp will just amplify it and you really don't want that going out over the airwaves. Jim/W5JO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Re: Carrier with one sideband
Vectors and resultant graphs are shown at this site http://www.qsl.net/wa5bxo/amtech.html John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Re: Carrier with one sideband
I think most of the modern rice boxes are actually full double sideband. By modern, I mean in the last 5 years. I have not seen any lately that or not full double SB, but I am sure there are still a few that use the filter and are SSB with carrier insertion regardless of mode. Actually TV is a mix mode thing. The first 250KHZ of modulation is full AM DoubleSB but then the rest of the 4.1 MH of modulation is SSB. At 3.58MHZ is the suppressed color subcarrier (not transmitted except in bursts)with double Sideband I/Q addition out to 500KC above and below the 3.58MHZ mark then another 500KC upper but only at the phase that produces skin tone. At 4.5MHZ out is the full FM audio subcarrier that is 150KHZ wide Interestingly the IF bandpass of the TV RCVR is a bell or flat top shape with the main carrier tuned at 50% down on one slope and the 4.5MHZ audio subcarrier in a trap right before after the sound IF takeoff. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bob Macklin Sent: Thursday, February 07, 2008 5:39 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Re: Carrier with one sideband The method of generating AM with a SSB transmitter by reinserting carrier was a common mode of operation in the late 50's and early 60's. The TV video signal works this way. It is my understanding the modern RICEBOXES that generate AM do it in the exact way. __ Our Main Website: http://www.amfone.net AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
