Re: [AMRadio] Audio response and Long distant QSO's (was: Suggestions Please)
One thing that happens when tuning an AM station with a narrow receiver is that you tend to tune off to one side to get more highs and less lows through to make it more intelligible. When you tune off to one side you cut off the other side band and you loose 1/2 of the power. That drops the signal down into the noise on a weak signal. With a signal that has proper pre emphasis the need to tune off to the side with the narrow receiver is eliminated and both side bands can be received raising the signal strength by 3 db. I have a TS430 with an AM filter in it. I think it is about 5 or 5.5 kc wide. When I listen to a very weak AM station in the SSB mode it is weaker than in the AM mode where I am receiving both side bands. There is less noise in the SSB mode using the product detector and the SSB filter but only 1/2 the audio power as compared to the wider AM filter. The AM filter is centered so that when I switch between AM and SSB I do not re tune the receiver. It is an interesting comparison. It can make the difference of being able to copy and not copy. 73 Gary K4FMX Bill Smith wrote: > Hi, Jeff > > > > Further, I have listened to AM signals from across the country, and usually > not with the TS-440. I will agree a few have been so bassy that they can be > difficult to understand, but overall signals with "50 to 5KHz" modulation > are overall so much easier to hear through noise that one wonders where the > notion of "communications quality" came from. There are some signals that > are so well processed (and frequency limited), and where the noise just > happens to be strong in a different part of the audio spectrum, or the voice > characteristic of the operator happens to overcome noise that such weak > signals cut through. Overall, in my experience, a full-fidelity signal will > be heard in most cases where a "communications quality" signal is torn up by > noise and fading. > > This goes for the receiver as well. The SX-62 is very wide, and the audio > capture from an am signal is obvious when compared with the TS-440. I don't > dislike the '440 at all, and use it all the time, but have observed that > even the wider positions of the Collins R-390 will allow better > understanding of a voice buried in noise. Maybe it is just my noggin, but > Mike Dorrough, K06NM would talk here about "power bandwidth," and Rich > Measures, AG6K would talk about "information bandwidth." > > A > 73 de Bill, AB6MT > [EMAIL PROTECTED] >
Re: [AMRadio] New link to Info on AM and legal power limits.
Nice write up John! Hmm, AM with reverse carrier control. Sounds interesting. That would look something like an FM signal but with only one set of side bands. Actually I have worked on some marine radios in the 70's that did do some reverse carrier control. They were SSB radios with AM capability. You could set the AM carrier level just about any level and when you modulated it would adjust the carrier down to the proper level. It was hard to make the radio sound bad on AM. I don't remember how the ALC was detected for the AM mode or exactly how the carrier level was controlled. I don't know if it would gain much but it would eliminate a little band noise when there was no modulation. ASYMMETRICAL AUDIO The fact that most of our voices are not symmetrical can be an advantage or disadvantage when modulating a radio. If the positive peaks are higher than the negative peaks then you will not over modulate in the negative direction while having positive peaks that exceed 100%. However if you are trying to run the legal limit power then it can be a disadvantage. Your average modulation level must be held low in order that the positive peaks do not cause you to exceed the power limit. Flopping the envelope over so that the negative peaks are higher than the positive doesn't help either. In that case you will over modulate before your average modulation level gets very high. The solution may be to make the modulation "more symmetrical". There are circuits consisting of several "all pass" filters that are supposed to do that. By having more symmetrical audio to modulate the transmitter with you will be able to obtain higher average levels of modulation without exceeding the power limit and not over modulating in the negative direction. It can also greatly reduce the need for large headroom in the modulator. Now add a little peak clipping and compression to the audio! You can increase the average audio even more while still keeping within the power limit and not over modulating in the negative direction. The broadcasters do it every day and most sound great. Of course it can't be overdone or it will not sound great anymore. Average power is what does the work in the audio. Those high sharp peaks are all but wasted. They add little to the sound of the signal. Especially on a crowded band. It is those high peaks that keep you from attaining the high average power that does most of the work. In RADAR there is a very high peak power to average power ratio. The reason being is that a certain pulse width and is needed to get the resolution. With a given pulse width the only way to increase the average power is to increase the peak power. Keeping the peak power the same and increasing the pulse width raises the average power which increases the range of the radar. But as the pulse width is increased the resolution gets poorer. (ability to distinguish between two targets) The point here is that it is average power that is important. 73 Gary K4FMX "John E. Coleman" wrote: > I've be working on a document that might be of interest to many folks. > With the help of K4KVY, WA3WDR, W5TOB and a month or two of night work > I've come up with something good I hope. Anyway here it is. > > http://www.qsl.net/wa5bxo/asyam/aam3.html > > I hope it is of some use to someone and encourages experimentation. > > John, WA5BXO > > > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio
[AMRadio] [Fwd: [Boatanchors] Johnson Ranger]
Saw this on another reflector. 73 Gary K4FMX Original Message Subject: [Boatanchors] Johnson Ranger Date: Thu, 03 Oct 2002 19:55:59 -0400 From: "Roland Hundley" <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] I have for sale, a Johnson Viking RANGER, I am getting out of AM..I want $200, that is a firm price..I will not ship, but will drive up to a 100 miles to meet someone..I am located in the Finger lakes of NY.. Please contact me by my e-mail address or phone call.. 585-526-6589 73' s RolandN2BIJ[EMAIL PROTECTED] ___ Boatanchors mailing list [EMAIL PROTECTED] http://mailman.qth.net/mailman/listinfo/boatanchors
Re: [AMRadio] Collins 32RA Transmitter
Hi Dennis, I didn't know about that one. I have a SSB point to point transceiver that has 4 fixed channels. It has circuitry similar to the KWM1 and KWM2. Rack mount and has a pair of 6146s in the final. It uses a set of tunable plug in coils for each channel. It is a 32RS1. I was told that less than about 15 or so of them were ever sold. 73 Gary K4FMX [EMAIL PROTECTED] wrote: > All, > > Looking for information on the Collins 32RA transmitter. This is an HF rig > designed to operate on 4 xtal (or ECO) fixed tuned channels in the range 1.5 > to 20 MHz. Three 807s in parallel in the PA modulated by four 6L6s > operating push-pull parallel. The earliest reference I have been able to > find is a 1939 QST advertisement, and I have been told that the rig was > included in the Collins product line into the early 60s. I have also been > told that many units appeared in MARS channels in the 50s. I would be > grateful for any information on production life, quantities, models, > military/government and civilian usage and anything else readers might wish > to pass along. I have an original manual, BTW. > > I am currently restoring one of these transmitters at the Ft. MacArthur > Museum in San Pedro, CA. The rig was used there in WW2 with a BC-779 receiver > to communicate with a HQ element in San Bernardino, CA. Also plan to do an > article for ER. > > Pictures available on request. > > Dennis D. W7QHO > Glendale, CA > > --- StripMime Report -- processed MIME parts --- > multipart/alternative > text/plain (text body -- kept) > text/html > The reason this message is shown is because the post was in HTML > or had an attachment. Attachments are not allowed. > Please post in Plain-Text only.--- > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] Central Electronics 20A Power Modification
Hi Jim, I have a 20A also. External to the 20A I use a pair of 1625s in AB2, grid driven, with a 4:1 toroide unun coil for the grid. Also some swamping resistors in the grid ckt. The 1625s drive a pair of 813s in GG. The mod sounds interesting. There is an article titled "shoes for the 10B" in one of the old CQ magazines around 1958 I think. The guy added a vfo in the 10B and a pair of 6146s! Forgot what he did for the power supply. I always found that when removing the 10k resistor across the 6BA7 that it would want to oscillate. Also found that the top cover (perforated shield) over the final and driver compartment had to be in place with all screws tight and the finger stock making good connection to the front panel or it wanted to oscillate. I have had several over the years and noted the same thing on all. Also the double shielded vfo cable mod that they came out with did wonders when using an amp behind the 20A. Kept it from getting RF back into the 20A. I wonder if you experienced any instability problems when putting in the new tubes? 73 Gary K4FMX Jim Candela wrote: > Hi all, > > I have been working on a 20a for some time now, and I'd like to share > something here with the group. > > The 20a has low RF output from the 2 X 6ag7 RF linear amplifier output. Mine > was about 3 watts AM carrier, or maybe 12 watts PEP on 80 meter SSB. Getting > a 600L linear amplifier is next to impossible, so I took another approach. > > I gave a 4 times 572 G-G linear that needs about 80 watts in for 800 watts > out (10 db gain). If only my 20A could put out more... > Using my linear on AM with the 20a gives me 30 watts, and heats the ham > shack. I did this for a while, and people laughed at me for such a silly > lash up. > > Here is what I have done: > > 1. replace 6ag7's with 7591's, and rewire tube sockets (could use 7868 with > socket type change) > > 2. Add extra B+ supply (200v from small 150 vac transformer, bridge, and > cap) in series with existing 300v for ~ 500v 7591 Plate voltage > > 3. Remove 10k resistor across 6ba7 tank circuit. This provides more drive to > 7591 grids > > 4. Adjust 7591 grid bias for -22 volts, and screen grid volts for 380 volts > > The results have been stunning: > > 50 watts CW output (B+ at 475V), or ~ 60 watts PEP SSB (B+ idles at 550v) > > 10 watts AM with plenty of headroom for > 100% + modulation. At 10 watts > out, each 7591 dissipates 15 watts (19 = max), and the % efficiency is 25% > (40 watts DC plate input for 10 watts rms output). The efficiency doubles at > 100% modulation (sine wave). > > 15 watts AM at 100% +/- modulation, and 150 watts from linear amplifier. > Efficiency a little higher here. > > The 7591 is about the size of a 6V6, yet has higher Gm (gain), and plate > dissipation. It fits nicely in the confined space of the 20a. Unfortunately > the 7591 can be pricey, as the audio nuts have bid the price up. Look on > EBAY, they are there. The 7868 is the same, and cheaper, but requires a > socket change. > > If any of you are interested in this, and want more details, just > contact > me, and I'll share it with the group. > > Regards, > Jim Candela > WD5JKO > > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] NC300 Oscillator Tracking Nightmare
With any oscillator, to get both ends right you need to adjust the capacitance at one end and the inductance at the other end. If it is spreading out too far , over compensate a little at each end each time you make an adjustment. Actually if you have an error of say 20 kc on one end, adjust for an error of 10 kc in the opposite direction. Then do the same at the other end of the dial. Several tries will get you there. 73 Gary K4FMX Mark Foltarz wrote: > Hey has anyone done an alignment on a NC300? > > I am having fits trying to get the dial tracking the > ocsillator. It seems impossible to get either end to > within 60Khz. > > I downloaded the manual from BAMA but I think there > must be a trick I'm not privvy to. > > Adjusting the oscillator coils by twisting that wire > in the middle of the form is really weird. > > TNX & 73 > > DE KA4JVY > > Mark > > > > __ > Do you Yahoo!? > Yahoo! Web Hosting - Let the expert host your site > http://webhosting.yahoo.com > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] "Reply" button got me...
Hi Larry and others, I too have a 20A. Have had several over the years. I found that to get good output on 40 meters that the 1625 has to be in very good shape. Being just a little weak makes a big difference. Also you need to adjust the padding coil (miniductor stock) that is across the 1625 tank coil in the vfo. You adjust it by spreading the turns on one end. If I remember right, the padding capacitor under the chassis needs to be peaked on 80 or 20 meters. The other bands are adjusted by adjusting the miniductor coils for maximum output. (It doubles or triples for other bands) It takes some messing with to get them right as the Q is pretty high. When you replace the top cover on the vfo things change so you have to compensate for that when adjusting. I watched the output of the transmitter (at less than full power) on a meter while adjusting the coils. Then watching how much it changes with the cover, you can get a feel for how much you need to adjust it in the opposite direction so it will be right with the cover on. Adjusting the coupling loop (knob on front panel) will detune the tank a little too on 40 meters. On one vfo that I have I tried slug tuned coils in place of the miniductor stock to see if they could be substituted. I found that the slug tuned coils in place of the miniductors did not give near as much output on the vfo so that was abandoned . I also tried to use a higher harmonic for 10 meters and shift the vfo with an additional padder capacitor (similar to what is done for 15 meters). I had a spectrum analyzer to watch all the harmonics at once but found that I could not get enough isolation. Some of the lower harmonics would end up in the output. I got it to work but tuning was very tricky and if not looking at the spectrum analyzer, the wrong harmonics would get right through the 20A. I gave up on that idea. I do have a vfo with the 10 meter kit in it. The crystal oscillator in it is run directly from the 20A's high voltage. When keying the transmitter that voltage drops some and the crystal oscillator starts to drift. I think that I tried running it from the regulated 105 volts one time but that dropped the output too low. I have never gotten back to it to try and solve the drift problem. Other than that it works pretty well on 10. I also have a Phase master vfo that I have yet to hook up. It is built on the 458 parts but rather than use harmonics they have separate crystals and heterodyne for the other bands. It may double on one band, I can't remember. The schematic of it is in Stoners SSB handbook. 73 Gary K4FMX Larry Szendrei wrote: > Mike et. al., > > My CE20A has about 1/2 the output on 40M as it has on the other bands > (160, 80, 20, & 15) in spite of the fact that the CE mods to cure this > in the VFO-458 have been implemented. As I recall the VFO output is > tripled for 40M, and only doubled or on the fundamental for the other > bands. My VFO doesn't have 10M capability, so have no experience with > 10M on this rig. > > 73, > -Larry/NE1S > > MIke Wells wrote: > > > > I'm enjoying the 20A discussion. I have a 20A that I want to get on the air > > so keep the messages posted here for the benefit of others. > > > > Tell me more about the VFO, are you having good luck with it on all bands? > > I've only got mine working on the low bands, no oscillation on 40 meters. > > Suggestions? > > > > 73, > > > > Mike W0FD > > > > Subject: [AMRadio] "Reply" button got me... > > > > Regarding the previous posting to the list: it was unintended. The old > > "reply" button got me again! > > > > If you're interested, read it. It's part of a discussion Jim Candela and > > I are having about a vintage SSB exciter, the venerable Central > > Electronics 20A. If not, the "Delete" button is much more predictable in > > its effects than "Reply." :>) > > > > 73, and back to AM... > > > > -Larry/NE1S > > > > ___ > > AMRadio mailing list > > AMRadio@mailman.qth.net > > http://mailman.qth.net/mailman/listinfo/amradio > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] DX-100 vfo
Hi Russ, Sounds like the dial has slipped on the shaft 180 degrees. When the dial is showing the frequency decreasing, the capacitor is opening up rather than closing the plates. I haven't looked inside one of those vfo's in a long time. If the capacitor can turn 360 degrees without hitting any stop, it may be just a matter of turning the dial 180 degrees to where you have the same capacity as before but you are on the opposite side of the dial. 73 Gary K4FMX russ dworakowski wrote: > To the group: I am having difficulty witha different VFO- a VF-1 > or same as used in a DX-100. I know you guys are talking CE20- just a > question- my VFO is tracking reverse in frequency- like when you go down > in frequency on the display, it is actually going up in frequency. > Is it possible that the end point adjustments are so far off that they > could cause this? Russ >
Re: [AMRadio] Today's AC Mains voltage too high for many BA Rigs
Hi John, I think that an "iron vane" type meter to read the voltage will give the true rms voltage no matter what the wave form is. 73 Gary K4FMX John E. Coleman wrote: I haven't seen any post about the saturated core constant voltage XFMRs. I use them a lot. They keep the OSCs on the RCVR and XMTR stable. I have never used one on a filament source for a directly heated cathode tube but since the output wave form is not a sine wave but somewhat squared due to the saturation of the core, I would assume the voltage would need to be reduced to arrive at the same heat on the filaments. They were easy to make. A lot of the hybrid TVs of old use power XFMRs with saturated core technology to keep the output voltages constant so that the picture didn't shrink or jump when the air conditioners or heaters would kick on. There was a 2 or 4 uF oil filled cap across part of a secondary winding that some what resonated and saturated the core. The input voltage could vary for 100 - 130 with very little change in the DC from the rectifiers. I would use the filament winds to buck or add to the output to get it where I wanted it to be. With one manufacture, I actually came up with 115 volts as read on a RMS meter. The scope showed it to be clipped about 10-15 percent. A light bulb test was made and found to be brighter on the constant voltage XFMT than on a variac delivering the same RMS measured voltage. This could be compensated for I would think. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Donald Chester Sent: Friday, January 17, 2003 11:53 AM To: amradio@mailman.qth.net Subject: Re: [AMRadio] Today's AC Mains voltage too high for many BA Rigs I have the problem here. I have seen the voltage as low as 108v and as high is 125. My main transmitter has a rheostat on the tube filament transformer line feeding several transformers, but I have the same problem, having to keep a constant eye on the thing and frequent adjustment. Incorrect voltage won't burn out tubes right away, but the manufacturers have warned for years that this will shorten useful tube life. One solution I have thought of, and probably have all the parts for, would be an automatic voltage regulator using a variac and reversible motor. I have a relay that looks like a meter, but the pointer has two sets of contacts, one of which will engage wenever the pointer is above or below the set value which is adjustable with a knob near the zeroing screw. It's just a matter of figuring out exactly how to build the thing and putting it together. Minus the special relay, I have thought about using a VR tube and comparing its voltage output to that of an unregulated power supply with the same nominal output voltage. Of course, it could also be done using solid state components. One thought about using a variac. With most of the ones I have used, even the HD ones, the regulation sucks. A tapped autoformer with a heavy duty switch is better. Instead of using the variac to drive the equipment direcly, it would be better to use a large, high current, low voltage transformer@ about 15-24 vac/ 30 amps as a bucking transformer and use the variac in the primaryof the transformer. That way you get better resolution of voltage and better regulation. The problem with variacs is the carbon brush contact. It must have a certain amount of resistance so that shorted adjacent turns don't overheat, since the wiper contact must make before break to assure uninterrupted output as the voltage is varied. Don K4KYV ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] Driver Xfmr
Hi Mike, If it is the primary of the transformer that opened (usually is) you can still use it to get you buy. Just put a resistor in the plate of the audio driver tube, in place of the transformer primary. I think around 10k 2 watt will work ok. Then couple the plate of the driver to the grid of one of the 1625s with a capacitor. Leave the secondary of the driver transformer hooked to both grids and bias as it was. It will work as an auto transformer to couple audio into both tubes. Works fine! Although gain will be somewhat less than with the transformer. Be sure to check to see what shorted to take out the transformer. Maybe the tube. 73 Gary K4FMX MIke Wells wrote: Hello, I just lost the audio driver xfmr in my DX-100. I turned it on to warm up and a few minutes later the house filled with the familiar smell. Anyone have a parts unit or advise as where I might find a replacement? Thanks Mike W0FD ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] Driver Xfmr
[EMAIL PROTECTED] wrote: In a message dated 2/6/03 7:25:39 PM, [EMAIL PROTECTED] writes: Just put a resistor in the plate of the audio driver tube, in place of the transformer primary. I think around 10k 2 watt will work ok. Then couple the plate of the driver to the grid of one of the 1625s with a capacitor. Leave the secondary of the driver transformer hooked to both grids and bias as it was. It will work as an auto transformer to couple audio into both tubes. Works fine! Although gain will be somewhat less than with the transformer. I've done this too with FB results as long as one is not trying to push any power into the next stage, but only providing a voltage swing. Never had a DX-100 so have to ask, in just what class are the 1625 modulator tubes operating i.e., AB1 or AB2? If AB1 the scheme under discussion (or a phase inverter, or an itty-bitty transformer) should work FB. Nada if AB2. Dennis D. W7QHO Glendale, CA Hi Dennis, The 1625s in the DX100 do go into AB2 to get full modulation. Thus the driver transformer used is a step down transformer. 3:1 I think. Using the resistor in the plate of the driver rather than the primary of the transformer only allows AB1 operation of the modulators as you say. You can not get full audio with that setup unless you reduce the power on the finals enough to deal with less audio power. 1625s put out considerable more power in AB2 than in AB1. Unlike a 6146, which will put out almost as much power in AB1 as it will in AB2. 73 Gary K4FMX
Re: [AMRadio] Re: Looking for Linear Amp
Geoff Edmonson wrote: I spewed my drink all over the monitor when on Friday 19 December 2003 01:41, [EMAIL PROTECTED] said (and I am -not- making this up!):: In a message dated 12/18/03 10:41:35 PM, [EMAIL PROTECTED] writes: It has been my experience that of everything is workig right, and the output circuit is efficiently designed, the maximum reliable power output from a linear amp running standard AM is about equal to half the total rated plate dissipation of the tube(s). i.e. for a pair of 6146's, 20-25W carrir, 80-100W PEP. Good rule of thumb. I've operated my home brew 3-1000Z linear on legal max AM. The tube is dissapating about 800 watts under carrier only condx in this mode and the plate runs a nice bright yellow-orange! Dennis. what are you calling "legal max AM"? The only legalities we have anymore, is 1500w PEP output. Depending on the natural asymetricalness of your voice, will depend on how much PEP output you have (which is quite difficult, at best, to measure). The Rule of thumb is, if you modulate a carrier to 100% with a sinewave, the Peak Envelope Power Output is 1,500 watts. That would the carrier power(x4). or 375w of carrier output, or (roughly) 500w DC input to the final. The problem with that is, we don't speak in sine-waves ;-) For more information on figuring PEP power, see http://www.qsl.net/wa5bxo/amplitude-modulation-and pep.htm For a great write up on asymetrical audio, see http://www.qsl.net/wa5bxo/asyam/aam3.html Dig around the website. Be careful, though - you might learn something ;-) Happy Holidays 73 = Best Regards, -Geoff/W5OMR Geoff, What's wrong with what he said? He is talking about LINEAR operation not a plate modulated final. His figures are correct for "rule of thumb". Remember 33% efficiency for the carrier in linear AM operation. 73 Gary K4FMX
Re: [AMRadio] ceramic standoffs needed
Aren't those the loading caps? If so there is no where near that kind of voltage there. Less than 600 volts p to p at 50 ohms. It is the current that is the problem. 73 Gary K4FMX [EMAIL PROTECTED] wrote: Sorry can't make it. Got a party to go to. These dang newbie and there Valiant's. Those caps gotta be rated at four times the voltage that's on the final minimum! 'gte --- StripMime Report -- processed MIME parts --- multipart/alternative text/plain (text body -- kept) text/html The reason this message is shown is because the post was in HTML or had an attachment. Attachments are not allowed. To learn how to post in Plain-Text go to: http://www.expita.com/nomime.html --- ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] ceramic standoffs needed
Hi Terry, Sorry I was thinking of the wrong end there. But the current at the plate end is even worse. Voltage would be 2 times dc voltage but the current is very high. Need transmitting mica caps there or doorknob ceramic. 73 Gary K4FMX [EMAIL PROTECTED] wrote: Hi Gary, I wasn't paying attention to where that piece of mail was going. It wasn't meant for the list. The caps in question are padders for the plate tuning not loading. Johnson in it's infinite wisdom four 500v caps in serise/parrell to make a 1kv unit which is still underrated. I figure 660v plate voltage + 150w of rf @ 8v a watt 1200v rf + 600v of audio in am mode. Add it all up and you get 2400v or four times the plate voltage on the final. So does that seem good logic to you? Terry N3GTE --- StripMime Report -- processed MIME parts --- multipart/alternative text/plain (text body -- kept) text/html The reason this message is shown is because the post was in HTML or had an attachment. Attachments are not allowed. To learn how to post in Plain-Text go to: http://www.expita.com/nomime.html --- ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] RE: r390a, sx17, t4xb for sale
High capacitance per foot on the cable. In the high impedance mike circuit a little capacitance will kill the highs. 73 Gary K4FMX Brett Gazdzinski wrote: The R390a is sold, Bob (wa3gfz) jumped on this one and picked it up last night! I have had that R390a for about 20 years, and its been working fine for the last 15 years at least, after a rash of broken gear clamps the first couple of years I had it. I hope Bob has as good a performance from it as I did. I don't know how things are normally done as far as selling, but I think Bob actually called my house first, and left a message with my son. I still have the like new SX17, which I thought sounds better than the R390a audio off the detector into the Marantz amp. I now have an almost empty rack for the new project, I may move the push pull 812a rig rack into its spot, if I can find a place for the audio power amp, the only thing in the rack now. Or, maybe I will leave the racks in place and move the 812A rig into the empty rack, its closer to the operating desk. The new rig (pair of 4D32) is coming along nicely so far, the RF deck is drilled, punched, and painted, just needs to be assembled, then its onto the RF control deck. I am making the decks so they can be used with anything, variac bias supply, variac screen supply, etc. The RF deck is 40 meters only, but if I want, I could build an 80 meter deck to go with the 40 meter one. The push pull parallel KT90 modulator deck is laid out parts wise, and I have all the parts needed for it. One power supply deck parts are gathered, I think I will do separate variac supplies for RF and modulator decks. I made an interesting discovery Sunday. I have had a few reports of my audio not having a lot of highs, even though I boost the mid and upper voice frequencies. There is nothing to limit the highs in any of the rigs, other than the mod iron, and even crappy mod iron will typically pass high enough frequencies to sound good, and found the cord between the mike preamp and the power amp was the problem. It was a 15 foot piece of rg8m, the little coax, with phono ends on it. You would think something that works for RF service up into VHF would be able to pass high audio frequencies, but no. I wonder why it was so poor for audio, cutting stuff above about 3000 cycles a lot Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Brett Gazdzinski Sent: Monday, January 12, 2004 11:13 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] RE: r390a, sx17, t4xb for sale ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] RE: r390a, sx17, t4xb for sale
The characteristic impedance of the cable is of little importance at audio frequencies. It is the capacitance that matters. If the circuit is a low impedance one then the capacitance does not matter much either. But in a high impedance circuit the capacitance becomes important. 73 Gary K4FMX Mike Dorworth K4XM wrote: 50 ohms is 50 ohms, plus 20 pf per foot cap all are killers! Mike,K4XM - Original Message - Subject: Re: [AMRadio] RE: r390a, sx17, t4xb for sale I have had a few reports of my audio not having a lot of highs, even though I boost the mid and upper voice frequencies. There is nothing to limit the highs in any of the rigs, other than the mod iron, and even crappy mod iron will typically pass high enough frequencies to sound good, and found the cord between the mike preamp and the power amp was the problem. It was a 15 foot piece of rg8m, the little coax, with phono ends on it. You would think something that works for RF service up into VHF would be able to pass high audio frequencies, but no. I wonder why it was so poor for audio, cutting stuff above about 3000 cycles a lot Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Brett Gazdzinski Sent: Monday, January 12, 2004 11:13 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] RE: r390a, sx17, t4xb for sale ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.560 / Virus Database: 352 - Release Date: 1/8/04 ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] RE: r390a, sx17, t4xb for sale
Most RF coax cable has a capacitance anywhere from 26 to 30 pf per foot. So if you had 15 feet of cable you had about 390 to 450 pf of parallel capacitance. The preamp output and amp input may be higher impedance than you realize. If you are feeding the output from the plate of the preamp it will be fairly high. The difference between audio and RF service is that in RF the cable is usually operated at its characteristic impedance. In the case of this cable 50 ohms. The capacitance and inductance in the cable work together as many tuned circuits. The loss is then limited to the AC resistance of the wire in the cable. The characteristic impedance of the cable does not come into play until it is some significant part of a wavelength. If you used a very short length of the same cable at RF it would look more like a capacitor. Just like it does at audio. At audio frequencies the cable would have to be several hundred feet long before its characteristic impedance would start to have any effect. So the dominant effect at these frequencies is the parallel capacitance that is in the cable. If the cable is used in a low impedance circuit then the 300 to 400 pf of capacitance may be insignificant. But if the same cable is used in a high impedance circuit, several thousand ohms, then the 300 to 400 pf of capacitance forms a good high frequency attenuator. 73 Gary K4FMX Brett Gazdzinski wrote: I know the D104 is very sensitive to the cable used, on mine, only the cable that came with the mike works well at all. This was on a line level link between the output of the mike preamp and the power amp, lowish impedance I thought. I measured the capacitance of the cable and got something like 10 PF? I think. And how would a cable be an efficient transporter of RF but not audio frequencies? Surely capacitance or inductance would impair RF more than audio??? Resistance is not a problem in rg8m... Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Gary Schafer Sent: Tuesday, January 13, 2004 12:04 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] RE: r390a, sx17, t4xb for sale High capacitance per foot on the cable. In the high impedance mike circuit a little capacitance will kill the highs. 73 Gary K4FMX ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] A Reminder - ALL PLEASE READ
Brian, Part of the problem may be that some of the ISP's have gotten bought out and a new email address is required for everyone. The old company still forwards the email via the old address for many months. I was subscribed on AT&T in the past. Comcast bought them out. I had to unsubscribe the old address and resubscribe with the new address at Comcast. If I had not unsubscribed and resubscribed with the new address, I would be still receiving the list but unable to post because of the new address. I just recently discovered that problem that I have on another list. (I forgot to unsubscribe and subscribe with the new address) I hadn't posted to it in some time but still receive the list and was unaware until I tried to post to it. AT&T still, several months latter, forwards mail addressed to the AT&T address. 73 Gary K4FMX B. Morgan Sherrod wrote: For those who use more than one email account, must use the one you entered when you signed up to this list when sending a post to this list. If you belong to more than one QSL.NET mailing list, and have different email accounts setup on each, then it is likely you will not be able to "CC" the other ones as well. I am getting a hoard of rejections from the list manager (software) that I have to sift through every day, simply because many posts are sent using the wrong (the one not subscribed to the AM List) account. PLEASE be more careful when you post to this (and other) list in regard to what account you are sending from. This is an "open" list, in other words, anyone can join, but you can only use the email account you setup. I do this so that we do not have SPAMMERs trying to either post to the list, or farm email addresses from the members. So far we have been blessed from that intrusion for the past several years. If anyone would like to suggest we make the list totally open to anyone "without membership", please, let's discuss it openly on the list for all to see. Thanks, Brian Sherrod W5AMI PS: I normally let the list flow without my intervention, and think that is a good policy. However, I must insist that we decide on what to do if so many folks want to post from different (those not subscribed) email accounts. ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] The PROPOSED ARRL Suggestions to FCC
Here is some food for thought: Back in the mid 60's the Air Force Tech school flunked some of the guys out that could not comprehend electronics. Those that flunked out were transferred to what was called "ditty bop" school. Ditty bop was where they made 20 wpm CW operators out of them. 73 Gary K4FMX : In fact I would be willing to bet that a chimpanzee could be taught code at 5 WPM!!! And I would be just as willing to bet that you could NOT teach a chimp to read a single schematic and build a circuit. at least not the SAME chimp... which, to me, speaks volumes for the NEED for a Morse Code requirement. To put it more bluntly, didn't the FeeCee learn from it's mistake in 1957, when they gave away the best DX band that Amatuer Operators had at the time? 73 = Best Regards, -Geoff/W5OMR ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
[AMRadio] Help id transformer
I picked up a little gadget at a hamfest. It looks to be a low pass filter for audio. Has 3 terminals. In, ground, out. Made by UTC. The number on it is UTC V-1284. Under that number is 363-1919G1. There is also stamped on the side HQ48. Can anyone identify this? Thanks Gary K4FMX
Re: [AMRadio] Help id transformer
Hi Jim, Thanks for the info. I didn't know that those catalogs were online. Some very good info in them. Unfortunately the little filter that I have is not listed in there. I did see some filters like this listed in an old Allied radio or WRL catalogue but not the number that I have. Still looking. 73 Gary K4FMX Jim Wilhite wrote: Hi Gary: Have you checked here? http://www.amfone.net/online.htm I am on dial up so the pages load slow for me. If I remember correctly you have broadband. If so you will be able to look much quicker. 73 Jim de W5JO - Original Message - From: "Gary Schafer" <[EMAIL PROTECTED]> To: "Amradio@Mailman.Qth.Net" Sent: Sunday, March 21, 2004 5:07 PM Subject: [AMRadio] Help id transformer I picked up a little gadget at a hamfest. It looks to be a low pass filter for audio. Has 3 terminals. In, ground, out. Made by UTC. The number on it is UTC V-1284. Under that number is 363-1919G1. There is also stamped on the side HQ48. Can anyone identify this? Thanks Gary K4FMX ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] RE: negative cycle loading
John, Good point about the screens on tetrodes. I had that problem when trying to modulate a pair of 1625's. When using the normal voltage dropping resistor to feed the screens, the screen voltage would cut off long before the plates went to 100% negative. Sounded terrible. I ended up with a voltage divider for the screens so that they did not receive as much modulation. Part of the screen voltage was obtained from B+ and part from the modulated B+. That worked fine once the proper values were found. I monitored the screen voltage with a dual trace scope to see when it got cut off. 73 Gary K4FMX John Coleman, ARS WA5BXO wrote: Bret, What Dennis is saying about the clipping is correct. It would seem that it is all a matter of degree. That is, less abruptness, in the clipping or limiting, means less higher order harmonics distortion and vise versa. There or other things that may cause splatter during high modulation. I have taken the liberty of making a list of check points that I use. You may be familiar with these, but here they are for the record any way. I have also used shaping circuits in the low level preamps of the modulation system. High capacitance Varicap diodes can do some really neat stuff in high Z low level circuits. Check points: 1. The Class C circuit that is being modulated may go into spurious oscillations at the positive peaks of the modulation and this may not occur until a certain voltage at a certain audio freq appears on the plate. It is more likely to happen if a circuits positive peaks or allowed to go higher than normal. The gain of the tube begins to increase a lot on positive modulation peaks. Cures 1. Make sure that the tube is capacitively neutralized well, and that there is no inductive feed back path. 2. Make sure that you have enough RF grid drive for the high positive peaks. As you raise and lower the plate voltage the plate current should follow linearly and so should the output RF. (no change in efficiency). 3. On tetrode tubes the screen should be modulated as well as the plate circuit but when the plate reaches double the quiescent positive voltage, the screen should only have reached 150% of its quiescent voltage. The same is true for the negative going audio. When the plate voltage has reached 0 volts on the negative audio peak, the screen should only have gone down to about 1/2 of its nominal value. The positive peaks here are the ones that will cause the tubes gain to increase causing any RF feedback to break into oscillation. The incorrect negative peak ratios may cause the tube to shut of quicker than normal. The exact correct ratio of plate modulation to screen modulation may vary from one circuit to another. 4. Reducing the load on a tank circuit so as to draw less plate current may cause the Q of the tank circuit to be increased and this will increase the possibility of spurious oscillations if any feed back can be found. The better way to reduce power is to lower the plate voltage (and screen supply if a tetrode) keeping the Q of the tank where it should be. 2. I have heard that it is possible that some of the splatter from over modulation (carrier pinch off) occurs when the plate current shuts off and the tank circuit is left to ring. I can see this to some extent and more so in high Q tanks but I would suspect this to be at a very low level only. Others may have more info on this? I think the majority of the splatter is audio harmonic distortion imposed on the modulated envelope. One thing is for sure. It is a good idea to provide a load for the modulation circuit after the final has reached below the zero plate voltage point on the negative peaks of the audio cycle. This can be done with a single HV diode in series with a resistor of the same resistance as Ep/Ip. This series network is place from the plate modulation point to ground so that the diode is reverse biased except when the voltage at the plate goes negative. This will do nothing for the ratio of positive to negative peaks of RF but it will help provide a load for the modulator during this period and keep the modulation XFMR from acting like a spark coil. Good luck to you on your experiments. And keep doing them, that's where everybody learns, especial when you share the experience. 73, John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, April 06, 2004 4:17 PM To: amradio@mailman.qth.net; [EMAIL PROTECTED] Subject: Re: [AMRadio] RE: negative cycle loading Brett, Are you using the three diode circuit at < http://www.amwindow.org/tech/htm/3diodeka.htm>? If so, this thing will clip all negative peaks that cross the "keep alive" level. How abruptly would depend on the internal impedance (i.e., stiffness) of the keep-alive supply but would give essentially the same effec
Re: [AMRadio] Test Equipment Recommendation
The Harbor freight meter can be had on sale for $19.95. I have one and it is ok. The other functions, capacitor, frequency etc. are almost useless though. The sensitivity and range for those functions are poor. But for a general dvm it is not bad. They do have a cheap one that they sell on sale for $2.95 ! It also has a transistor test function that works pretty well. That meter is just as accurate as any of the others. A great buy. The fluke RF probe is limited to 30 arms and 200 vdc. Have to be careful on a boat anchor. I have been buying several dvm's lately. Kind of went overboard. Got some expensive fluke and HP stuff (all used). The best buy I have found for a bench meter at a low price is the fluke 8050A. It is very accurate, 4 1/2 digits and has some nice features like db ranges and one button offset. These can be had for $20.00 to $40.00. They are true rms on AC also. The only thing it doesn't have is auto range. You have to manually select the range. The 8050A is much more accurate than any of the handheld series that they now make, under $300.00 Another sleeper that is very nice is the HP 3466A, or 3465A same thing different case. It is an auto range meter with similar specs to the fluke 8050A but no db range or offset button. (used, not made anymore) I also have a fluke 87-3 which is a 3 1/2 digit meter or a 4 1/2 digit meter in the high resolution position. Trouble is that it is +- 10 counts, which is 3 1/2 digit accuracy. The 8050A is true 4 1/2 digit at .03%. O well, enough on that. My other favorite in low cost would be the HP 410B. You can't hurt the rf probe on a boat anchor with the high voltages. If an RF probe for a boat anchor is what you want the HP 410B or C would be the choice. 73 Gary K4FMX James M. Walker wrote: Well, You could go to Harbor freight and buy their high end digital voltmeter, which does AC and DC volts, measures inductance, and capacitance as well as resistance for 39.95. Then buy the Fluke RF-80 probe for around the same cost and there you have a fully functional test device. Jim WB2FCN - Original Message - From: "Merz Donald S" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Tuesday, August 24, 2004 10:21 AM Subject: RE: [AMRadio] Test Equipment Recommendation Really? Is this the best recommendation that we can come up with? Every one of these that I see is awfully beat up after 30-50 years. And these were not especially high quality units to begin with. On the other hand, I don't know what else to recommend. I am using an old Radio Shack Micronta VTVM, probably from 1970. I've had a Simpson 303 (these do not age well--to be avoided) and the RCA VoltOhmyst in several different flavors, plus several other brands. The Micronta has delivered the most reliable, accurate service of any of them. But I can't really recommend that because nobody could ever find one. Given the advanced age of the VTVMs that survive today, this actually is a harder question than it first seems. 73, Don Merz, N3RHT -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Edward B Richards Sent: Monday, August 23, 2004 11:27 PM To: [EMAIL PROTECTED]; amradio@mailman.qth.net Subject: Re: [AMRadio] Test Equipment Recommendation Bill; Go to that auction place and buy a Heathkit VTVM. There are usually a lot of them listed. All are 11 megohm input impedance. Then buy an RF probe. The later VTVM's have a phone jack input and so do most RF probes. Also known a demodulator or scope demodulator. Good luck 73, Ed Richards K6UUZ On Mon, 23 Aug 2004 19:30:22 -0600 (GMT-06:00) Bill Pancake <[EMAIL PROTECTED]> writes: Would appreciate a recommendation as to make and model of a VTVM that will come with an rf probe that is suitable for using when working on boatanchor gear. I just need an idea of what to look for. Thanks, Bill, [EMAIL PROTECTED] __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net The information contained in this e-mail may be confidential and is intended solely for the use of the named addressee. Access, copying or re-use of the e-mail or any information contained therein by any other person is not authorized. If you are not the intended recipient please notify us immediately by returning the e-mail to the originator.(B) __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing lis
Re: [AMRadio] B&W 5100B Modulation Update
Tom, Try a new rectifier tube if you have one and see what you get. Easy way to check capacitors is to tack a new one in parallel with the hv filter cap and see if you get any improvement. Does the 5100 have a meter position for modulator plate current? If so what is it doing. If you have the wrong impedance taps on the mod transformer, the modulators may be drawing much more current than they should. Too high an impedance tap into a low impedance final load will make the modulators draw very heavy current. 73 Gary K4FMX Tom Elmore wrote: The caps are the first thing I should have checked and there is a good possibility they are dried up except I don't hear any hum in the audio when monitoring on the receiver. Also I can make at least 125 watts carrier and don't see much of a voltage drop on B+ when I run carrier only. -Tom - Original Message - From: "George Pritchard" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Wednesday, October 13, 2004 8:46 AM Subject: RE: [AMRadio] B&W 5100B Modulation Update Tom, It seems to me that the capacitor bank for the 600 volts is not working. Look at the B+ with a scope, and you may see the B+ drop at the audio rate. A "stiff" capacitor bank will show no audio waveform on the B+. If I'm right, the caps are died out. Is there any trace of Hum on the "dead carrier"? George AB2KC -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Elmore Sent: Wednesday, October 13, 2004 12:35 PM To: amradio@mailman.qth.net Subject: [AMRadio] B&W 5100B Modulation Update Now that I have had some time to troubleshoot the B&W 5100B modulation here is what I found. The B+ is around 600 volts with no modulation and I as start to modulate and watch the scope when it reaches about 50% modulation the B+ drops from 600 to around 400 volts. I changed the final and modulator 6146 tubes and see the same results. The original modulation transformer has been replaced with a Chicago Standard Transformer Corporation # A-3891. When I remove B+ to the final's and terminate the modulation secondary into a resistive load of about 6k ohms I still see a significant drop in B+ as I start to bring modulation up. I don't have the original mod transformer and the manual I have doesn't say what the impedance should be. I have tried various other tap settings on the transformer secondary and don't see much of an improvement in reducing the amount of voltage drop. I wonder if it is possible that this mod transformer just will not work with this unit. Anyone have experience with mod transformers using 6146's as finals and modulators? Thank You Tom Elmore KA1NVZ Anchorage Alaska __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] B&W 5100B Modulation Update
Tom, Let us know what that modulator plate current actually is at about 50% modulation and at 100% modulation. Awhile back I played with a pair of 6146's modulating a pare of 1625's with a multitap mod transformer. I found that using too high an impedance tap on the secondary, to get a lower ratio, would make the modulators draw lots of current. I could easily draw 400 ma of mod current or more. A partially shorted mod transformer could give the same results. Your idle current on the mod tubes should be around 50 ma? Maximum current with a whistle should go to around 250 to 300 ma?? The impedance ratio I would think (off hand) should be around 5000 or 4000 ohms plate to plate on the mod side and 2000 ohms on the final side. Assuming running 180 watts input (300 ma) on the final. 73 Gary K4FMX Tom Elmore wrote: Yes there is a plate current position and it shows a definite rise in current with modulation. There are dual 5U4's in the supply feeding the finals and modulator and I swapped them both out with the same results. I am leaning towards Gary suggestion that there is an impedance mismatch causing excessive current draw. Does anyone have a 5100B or know what the impedance of the primary and secondary should be. I will try another set of caps this evening when I get home there are 2 , 40uf in series on the B+ line. - Original Message ----- From: "Gary Schafer" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Wednesday, October 13, 2004 10:29 AM Subject: Re: [AMRadio] B&W 5100B Modulation Update Tom, Try a new rectifier tube if you have one and see what you get. Easy way to check capacitors is to tack a new one in parallel with the hv filter cap and see if you get any improvement. Does the 5100 have a meter position for modulator plate current? If so what is it doing. If you have the wrong impedance taps on the mod transformer, the modulators may be drawing much more current than they should. Too high an impedance tap into a low impedance final load will make the modulators draw very heavy current. 73 Gary K4FMX Tom Elmore wrote: The caps are the first thing I should have checked and there is a good possibility they are dried up except I don't hear any hum in the audio when monitoring on the receiver. Also I can make at least 125 watts carrier and don't see much of a voltage drop on B+ when I run carrier only. -Tom - Original Message - From: "George Pritchard" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Wednesday, October 13, 2004 8:46 AM Subject: RE: [AMRadio] B&W 5100B Modulation Update Tom, It seems to me that the capacitor bank for the 600 volts is not working. Look at the B+ with a scope, and you may see the B+ drop at the audio rate. A "stiff" capacitor bank will show no audio waveform on the B+. If I'm right, the caps are died out. Is there any trace of Hum on the "dead carrier"? George AB2KC -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Elmore Sent: Wednesday, October 13, 2004 12:35 PM To: amradio@mailman.qth.net Subject: [AMRadio] B&W 5100B Modulation Update Now that I have had some time to troubleshoot the B&W 5100B modulation here is what I found. The B+ is around 600 volts with no modulation and I as start to modulate and watch the scope when it reaches about 50% modulation the B+ drops from 600 to around 400 volts. I changed the final and modulator 6146 tubes and see the same results. The original modulation transformer has been replaced with a Chicago Standard Transformer Corporation # A-3891. When I remove B+ to the final's and terminate the modulation secondary into a resistive load of about 6k ohms I still see a significant drop in B+ as I start to bring modulation up. I don't have the original mod transformer and the manual I have doesn't say what the impedance should be. I have tried various other tap settings on the transformer secondary and don't see much of an improvement in reducing the amount of voltage drop. I wonder if it is possible that this mod transformer just will not work with this unit. Anyone have experience with mod transformers using 6146's as finals and modulators? Thank You Tom Elmore KA1NVZ Anchorage Alaska __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net _
Re: [AMRadio] AM Usage with Linear AMPS
Brian, What he is saying is: you need to have the 811A tuned up at 200 watts output on cw or pep for a 50 watt carrier out. (pep is 4 times carrier) When you tune up you tune it for max output at the 200 watt level with full drive. At that tune setting the tube will be around 60% efficient. Normal ssb or cw operation tune-up. input power will be 333 watts. The tube will be dissipating 133 watts in heat at full carrier. You then reduce the drive until you have 50 watts out (1/4 the carrier of full output). You can not retune at this point or it will not handle the peak envelope power of 4 times carrier. At 50 watts out the efficiency drops to around 30%. So that means to get the 50 watts out the tube has to be running around 150 watts input. 150 watts minus the 50 watts output leaves 100 watts to dissipate in heat in the plate as long as the carrier is on. It doesn't get any better either. With modulation the dissipation does not decrease even though the efficiency increases at the peak power levels. The carrier power is still there 100% of the time at 30% efficiency. The audio is in the form of separate side bands that is additional power that the tube has to handle. I guarantee you that an 811A will run with a red plate under these conditions. If it is not red then it is not tuned up properly for this mode of operation at the 50 watt carrier out level. 73 Gary K4FMX Brian Carling wrote: On 22 Nov 2004 at 20:23, [EMAIL PROTECTED] wrote: Going to shorten it's life considerably. Theoretically maybe. Have you tried it. How can you know for sure? Theory says a bumble bee can't fly. My 811A tubes never burned up. Where did you get your 30% number from? Who transmits their AM with carrier only!? I can't see how a 50 watt carrier input will cause an 811A to DISSIPATE 100 watts! Where are you getting the additional 50? To properly adjust a linear amp for AM it is necessary to tune the thing up for the peak power level, i.e., 200 watts for a 50W carrier. The linear will be about 60% efficient at this output level. Then WITHOUT CHANGING THE TUNING adjust the output from the AM exciter to provide for 50W out of the linear with no modulation. The problem here is that the linear will now only be running about 30% efficiency under carrier-only conditions and the 811 would be dissipating something like 100+ watts. The 811A, of course, is only rated at 65 watts. Dennis D. W7QHO Glendale, CA __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] AM Usage with Linear AMPS
Sweep tubes are a little different animal. They are designed for high peak power levels in TV sweep circuits. SSB has a pretty high peak to average power level. The average power is only in the order of 10 to 20% of pep. Unless you run heavy processing and then the sweep tubes will take a dive. They don't like AM very well either as the average power is much higher on AM. Tuning up an old swan at 500 watts you don't want to leave the carrier on very long. Tune quick and get rid of the carrier. There have been many sweep tubes cooked on tune up by being too slow twisting the knobs. 73 Gary K4FMX Brian Carling wrote: Aren't there a lot of commercially built amateur radio linear amplifiers and RF finals that exceeded he manufacturers MAX Pdiss rathings over the years, by adding a COOLING FAN to take away the extra heat? One thinks of MANY sweep tubes rated for so-called Pdiss of 16 watts and 20 watts that are regularly run at hundreds of watts of RF! The tubes don't seem to melt. I think of the ubiquitous 6JS6C with a rating of 30 watts. Yaesu ran a pair of these at 260 watts input in their FT101 series. Many guys ran them at 260 watts p.e.p. on SSB and 260 watts CW. Assuming 65% efficiency, you have 35% of 260 watts going into the plates. That is to say 91 watts split between the two tubes. UH oh - POP! But no, they didn't. Then when you throttle that FT-101 back to 40 watts input on AM and go to your 30% efficiency (if it is) then you are actually putting only 20 watts carrier per tube which is SAFER. Is that correct? How about some of the othre rigs that rated their 2 sweep tube finals for 560 Watts or even 800 watts!? Then youhave peak Pdisses of 140 to 200 watts between the two sweep tubes, most of which are rated for no more than 40 watts. On 22 Nov 2004 at 21:29, John Coleman, ARS WA5BXO wrote: I've got to get in on this HIHI. Some readers may not fully understand what you guys or talking about. So I will try to confuse it all some more. HIHI Plate dissipation is the heat that the plate of a tube is emitting. The manufacture of the tube has what is known as max plate dissipation limits. The 811A triode has a limit of about 65 watts. This means if the tube is in a circuit where it is putting out a steady carrier and this circuit is 75% efficient at is max level this would be 4 X 65 input power (Ep X Ip) and 3 X 65 output power (as measured by a RF Watt meter with no reflected power). This would be 260 watts input and 195 watts output with 65 watts wasted in heat of the plate. This would not be bad for CW. I don't think 75% efficiency is an achievable figure in a good linear operation even on peaks. As the drive level is reduced so is the output level (linearly we hope) but the plate current will not drop as fast. As a result the efficiency drops and it is possible for the plate dissipation to be greater even though the plate current is less. It is not a good idea to operate at the point where the plate dissipation is at its highest. In any linear amplifier audio or otherwise, proper design would be, to not exceed the plate dissipation at any time. How ever we all know that plate dissipation limits can be exceeded for a short duration provided that there is an equal or more amount of time that has a much less plate dissipation than the rating and that the time intervals or close enough to keep the overall temperature down on the tube. Exceeding Plate dissipation causes excessive secondary emissions and internal grid leakage. It is also the biggest cause of vacuum loss because of leaking seals at the anode connection. Poor vacuum causes more grid leakage and emission loss due to corroded heaters. Over temp on a tube is not good even for a short period of time. In a class B circuit with no input or output the plate dissipation must be below the limit. If the input is varying as it is with SSB or audio then the tube will pass through an area of much higher dissipation. This area is generally (but not always) somewhere near the 50% mark of peak drive and output. This means, the tube could actually be hot with just a carrier and, then cool down when the input is modulated with a tone. As I recall 811s do not (or just barely) show color at 65 watts dissipation. This would be static 2000V and 32 ma or 1500 volts and 43ma. Good practice would be to set bias some what below current for 65 watts dissipation. As input carrier is introduced a output carrier will also be created. It should be a linear progression until top end is met. During this progression the tube will go through various levels of efficiency and plate dissipation. Some of the places will be very close to or exceeding the limit of 65 watts. A point of best operation would be where the output is 25 % or less of the peak output POWER level (OR 50% of the RF output VOLTAGE) and the plate dissipation (input power
Re: [AMRadio] AM Usage with Linear AMPS
Geoff/W5OMR wrote: When you tune up you tune it for max output at the 200 watt level with full drive. At that tune setting the tube will be around 60% efficient. Assuming Class C about 60 to 70% yes. No. Class C is typically 70 to 75%. 60 to 65% is more likely for linear (AB1/AB2) operation. I have run a P&H Linear amplifier at these levels and even the 837s didn't glow red. But it may have been a little below 200 watts carrier. I only had it for a few weeks so it would not be a fair test. Thanks for explaining it in more detail for me. I just remember QST articles where a single 811A was run at 200 watts input as a linear amplifier or CW final and it did fine. The QST articles were probably talking about SSB or CW out of a single 811A at the 200w area. More than likely, it AM wasnn't considered in that test (*noting that QST is a publication of the ARRL, who would for a l-o-n-g time would NOT recognize AM as a valid mode of operation.) Maybe it was more than 30% efficient... that part still mystifies me! Sometimes I am dense though. Plate Voltage (Ep) * Plate Current (Ip) = DC Input. So, your quad 811A amp is running 1500v @ 400mA, you're running 600w DC input to the final. 150W per tube. That's to the max. When you tune the amp up for AM operation, leaving the amp at that -exact- tuning range, reduce the drive until you see only 150w, and probably a little less, to handle any asymmetry/transients in your voice*. 150W, modulated to 100% is around 600wPEP, but we're still talking DC INPUT, when you look at the 150W. So, 150 * 60% = around 90w of carrier output, which would be around 360W PEP output. Your mileage may vary, depending on Ep and Ip. If you just -have- to run a linear amplifier, instead of building up a plate modulated rig, at a MUCH higher efficiency rating, then build something with BIG tubes in it, that would handle the dissipation. like a pair of (or 3) 450TH's. 450W of plate dissipation, each. That'd bring you back up to the 1.5kW PEP level. That just might be a nice project... I could make a quad 450TL amp, and drive it with my Kenwood TS-680S I use mobile. (what a waste of a good tube!) 73 = Best Regards, -Geoff/W5OMR When you reduce the drive for AM operation you want to reduce the OUTPUT to 1/4 power, not the input power. The input power will be somewhere around 1/2 of full power when properly setup for AM. 73 Gary K4FMX
Re: [AMRadio] AM Usage with Linear AMPS
Donald Chester wrote: It doesn't get any better either. With modulation the dissipation does not decrease even though the efficiency increases at the peak power levels. The carrier power is still there 100% of the time at 30% efficiency. The audio is in the form of separate side bands that is additional power that the tube has to handle. Actually, it should get better. A properly operating amplifier with low level modulation, linear or grid modualted, should run a steady carrier output level and a constant DC input level, regardless of modulation. For the sake of discussion, let us assume 100 watts carrier output. The DC input will be about 300 watts @ roughly 30@ efficiency. With no modulation present, we have 300 watts input with 100 watts output. That leaves 200 watts dissipated in the tube plates. Now let's modulate 100% with a sinewave tone. The average rf power output will now be 150 watts, 100 watts carrier power plus 50 watts average sideband power. The DC input is still 300 watts, so the tubes are now dissipating only 150 watts as opposed to 200 watts with no modulation. The overall efficiency of the amplifier rises from 30% to 50%. If the tube plates are showing a glow, they should actually dim a little with modulation. Of course, the instantaneous efficiency is constantly varying over each cycle of the envelope waveform, from 0% at no output, to approximately 60% at maximum peak output capability of the amplifier. But it is AVERAGE power that determines how red the tube plates get, how loud the signal sounds over the air, and how much interference the signal produces. That is why the FCC's method of determining power output by p.e.p. is bogus. Don K4KYV Don, You are exactly right. I stand corrected. I remember that grid modulation are sometimes referred to as "variable efficiency modulation". The same principle applies to linear amplifiers with AM. When reducing power out to 1/4 as required for linear amplification the efficiency must drop to 1/2 of what it was at full carrier. At 100% modulation where 1/2 again as much power is in the output due to the audio, the efficiency also increases by 1/2 again as it is with only carrier. Like you said, the additional output comes from the plate dissipation as the input power stays the same. You rounded your numbers a little so the math does not come out exact in your example. But for those who wish to do their own: If an amp has 60% efficiency at full carrier reducing the output to 1/4 carrier will run it at 30% efficiency for the carrier. (exactly 1/2 the efficiency) 100% modulation will produce 50% more output and the efficiency will increase by 50% to 45%. (This is with a sine for modulation) These efficiency ratios must be maintained for linear operation. If the drive to the amp is not reduced to where the efficiency drops in half with the carrier, you will not be able to obtain 100% modulation without clipping in the amp. This is why you don't want to re-peak the output tuning on the amp when you reduce the drive. You change the efficiency when you retune. The carrier efficiency must be maintained at 1/2 the efficiency of full carrier which is the same level that modulation peaks will hit at full modulation. Orr explains it very nicely in the Radio Handbook in the modulation section. 73 Gary K4FMX
Re: [AMRadio] Ham Embarrasment
Geoff, How do you get on the mailing list for remote operation? Thanks Gary K4FMX Geoff wrote: I get mail from Keith LaMonica, because I'm interested in the remote HF radio operation. He's got a mailing list, dedicated to just that. This was in that list. 73 = Best Regards, -Geoff/W5OMR --- To TIME recipients: An article in your TIME magazine by Lev Grossman has been forwarded to my office. http://www.time.com/time/archive/preview/0,10987,1009913,00.html I do believe that Mr. Grossman has grossly been mis- informed and for such a prestigious magazine such as yours, one would think this type of gross error would have been avoided. Amateur Radio has been a magnificent hobby since the early 1920's for electronic experimenters that work tirelessly in their home labs and stations to break barriers and bring new technologies to the consumer world, not to mention the many uses the amateur radio operator achieved from these advances. If Mr. Grossman would do his homework, he would have discovered that what he refers to the 'embarassing' hobby was the platform for many of the devices he relies upon today. Amateur radio was many of the early engineers college education. Amateur radio operators, turned professional electronic engineers brought the world, most of the early technologies that brought us the radio receiver, the technology of television, the VCR - audio and video, high powered transmitters for AM, FM radio and TV stations, the complicated antenna systems used to transmit those signals, high powered audio amplifiers used in high fidelity and live concert stages and the list goes on. It was Art Collins W0CXX that brought Single Sideband technology to radio communications that carry vital communications world wide - from Air Force One, to virtually every transmission made by our government embassies around the world and every major commercial airliner in the sky. The late Arthur Godfrey, General Curtis Lemay, NBC space correspondent Roy Neal, Walter Kronkite, several of our US senators, many entertainers such as Joe Walsh of the Eagles, Patti Lovelace, Dave Bell, Hollywood movie Producer, Ronnie Milsap, baseball great Joe Rudi all the way to the late King Hussein, JY1 are just a 'few' of the many amateur operators that lives have been enriched AND, have enriched each and every person on the globe, including Mr. Grossman by Amateur Radio. NONE of this would have been accomplished as quickly and as economically if it were not for these early pioneers that spend countless late night hours in their home labs and stations. Embarrassing? You make the decision. I think this opens the door for the decision makers at TIME Magazine to do a feature article on the high level of technical expertise the great hobby of amateur radio brings to the world and I have not even touched upon the amazing amount of volunteer work that the 'hams' of the world brings to disasters. If it were NOT for ham radio operators volunteering their time and equipment in the heart of hurricanes, storms, disasters of all kinds many more lives would have been lost AND life line communications were established immediately in these areasand this continues today. Does Mr. Grossman call saving and affecting thousands of lives embarrassing? Obviously he does. I think it is time for TIME Magazine to rethink his horrible and erroneous statement and bring the REAL truth along with an apology to it's readers and the several million amateur radio operators world wide. I remain at your service to help you provide the truth about Amateur Radio. Best Regards, BOB HEIL, K9EID __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] AM Amps
Here is a ruff rule of thumb for amps on AM: If the amp takes 100 watts to drive it on ssb then it will take 100 watts pep of AM to drive it. 100 watts pep of AM means 25 watts of carrier with 100% modulation. You will also get 25% of the carrier out of the amp from it's pep output level. If it puts out 600 watts pep (collins 30L1) then you will get 150 watts carrier out when properly set up. If it took 100 watts pep to drive it on ssb it will take 25 watts carrier on AM. To see if the tubes will handle it figure the dissipation backwards. At 150 watts output that amp should be at around 33% efficiency (if properly tuned). 150 watts divided by 33% = 454 watts plate input power. Now subtract the 150 watts of output power you are getting from the 454 watts input power and you have around 304 watts going to heat in the plates. In the case of the 30L1 divide that by 4 (the number of tubes) and that leave about 76 watts per tube in dissipation. 811A's have a 65 watt plate dissipation ratting. So you are a little over. For short transmissions you can get by with it but no long buzzard transmissions. The power supply in the 30L1 is marginal also. It will get mighty hot. The other Gary's suggestion of limiting to 125 watts carrier out (500 watts pep)gets you right in the ball park on plate dissipation. 125 divided by 33% = 378 watts input. Subtract the 125 watts and that leaves 253 watts dissipated. Divide by 4 and that is about 63 watts per tube. For proper loading on the amplifier operating at 125 watts out with carrier it should be tuned for 500 watts output pep. The drive required can be figured pretty close by first calculating the gain of the amp at 600 watts output, its rated output. If it takes 100 watts to drive it to that output power that is a gain of 6. At 500 watts out the amp will still have a gain of 6 so divide 500 by 6 which gives about 83 watts pep of drive. divide that by 4 for the carrier needed. That should be around 20 watts. Keep in mind that the amp needs to be tuned at the pep level. One way to do that is to modulate the 20 watt carrier 100% with a tone or a long hlooo and tune the amp watching a scope. Another way is to use the ssb rig with an 80 watt carrier driving the amp and tune it for max output. Then hook the AM rig up with the 20 watts drive. You can roughly check to see if you tuned the amp right by looking at the efficiency that it is running when you think you have it tuned. Calculate the input power, plate current times plate volts. Divide the output power you are seeing on the watt meter by the input power. If the efficiency is around 30 to 35% you should be in the ballpark. Any greater efficiency and it tells you that amp is not loaded heavy enough. Or you have too much drive. More than you wanted to know. 73 Gary K4FMX Gary Blau wrote: I partially disagree, but with a -big- proviso. You'll have to find a way to reduce the Ranger output to the 10-15 watt level. Maybe the nicest way to do that is a variable screen voltage control, similar to what you'll find here: http://www.w3am.com/ranger.html but I'm sure there are other methods. Just don't run the stock Ranger straight into the amp without dealing with this in some way. Don't ask the 30L1 to do more than ~125 watts carrier. The 811's can't handle much dissipation. Same is true for the SB200 and its pair of 572B's. But they both will work fine like this. I ran an SB200 like this for a long time. Bigger amps with more plate dissipation, like the Henry or SB-220 are a safer bet, but you must be very careful nonetheless. 73, g Chris wrote: Hi Dick The 30L1 would far too over stressed but the Henry would be perfect, by the way thanks for buying my Ranger, 73 Chris RICHARD W GILLESPIE wrote: I just bought a Johnson Ranger and wonder if my 30L1 or Henry 2KD would work okay. 811's in the 30L1 and a pair of 3-500's in the Henry. Thanks. Dick/K5DIC
Re: [AMRadio] AM Amps
By "legal power out of the 813's" I assume you mean 375 watts carrier? If so there is no way the peaks are going to 1500 watts. A pair of 813's will not put out that much power in GG linear configuration. At least not very long. A pair of 813's in GG are good for about the same power out as 4 811A's. If you run them with more than 150 watts carrier out you will be flat topping with modulation, unless you keep the mod percentage very low. AT 375 watts carrier out at 33% efficiency that would require 1140 watts plate input power. That would be a plate dissipation of around 380 watts per tube! Cooked to well done in minutes! Now if you tune them so there is higher efficiency, the plate dissipation will be lower, but then your mod peaks will never reach any where near 100%. Even if your driver is modulated 100%. In AM linear service the efficiency of the amplifier must be 1/2 as much for the carrier as it is for the peaks. This is how the voltage doubles to obtain that peak power needed. Without that ratio you will have distortion and splatter. As you noted when running 600 watts carrier out you must back the modulation down. At that power level you have almost no headroom at all for audio. You are at near maximum capability of the tubes with just carrier. 73 Gary K4FMX ronnie.hull wrote: This aint rocket science at my shack. I have a pair of trusty old 813's in grounded grid with 3200 Volts on the plates. I drive them with my Ranger all the time with no problems at all. I always tune the ranger up to full power into a either a dummy, or my dipole. THEN switch the 813's into the line and then quickly dip the ranger. It usually will dip back to about 80'mils. I leave it right there and get legal power out of the 813's. If I want to bring the Ranger back up to full power, I can and it will drive those 813's to 600 watts and sounds great. I have been using this combination for 6 years and many of you have heard me on it. If I DO bring the ranger back up to 120 mils, I have to be careful of the audio drive, as it will tend to start to distort if the gain is up to high. But if I leave the Ranger at 80 mils, it works fine and I work coast to coast! Gotta love those old 813's! 73's de W5SUM __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] AM Amps
I know full well that there is no such thing as a 375 watt carrier limit to AM power in the FCC rules. I never said there was. I was trying to "clarify" Ronnie's statement about how much power he runs his 813's at when he says he runs them at legal power out. And since we don't know if Ronnie has a symmetrical voice pattern or otherwise, we can only assume it is symmetrical when discussing general power principles. Maybe he has the peaks phased so maximum peaks are in the negative direction? I don't know. Either way it appears as though he only has enough headroom for less than 50% modulation in the positive direction. On top of that the plate dissipation is around 380 watts per tube if the amp is tuned properly, which it can't be if it is not burning up tubes. That is the whole point, if you are paying attention. :>) Maybe you could tell us how much peak envelope power would be available from a pair of GG 813's at 375 watts carrier out with 100% modulation? 73 Gary K4FMX Geoff wrote: Gary Schafer wrote: By "legal power out of the 813's" I assume you mean 375 watts carrier? Why assume something that is false?? That statement is -designed- to put you on edge, Gary. Perhaps it's just my perception, but it simply appears as if you're not paying attention. NO WHERE does it say that 375w of carrier is the 'legal' limit. The LEGAL limit is 1500w PEP output. It's just a point of reference, that if you modulate a 375w signal with a sine-wave to 100% audio, then you will reach 1500w pep output. The truth of the matter is, we don't -speak- in sine-wave. Our voices are rather asymetrical. Some of us have voices that are rather 'peaked'. In order for the audio amplifying equipment to properly modulate 375w of carrier, instead of needing to only be 50% of the carrier, or 187.5w of needed audio, you -might- wind up needing an audio system with the capability of producing upwards of 600w of AUDIO. (ref: http://w5omr.shacknet.nu/~wa5bxo/asyam/Amplitude%20Modulation.htm) THIS IS NOT TO SAY that you'll be pushing your positive peaks that high, but in order to keep your signal clean, and well within "good engineering practice", you certainly don't want any flat-topping or distortion. Anything in the audio system that does -not- allow your audio to be clean and free of distortion then, by definition, wouldn't be operating within "good engineering practice". 73 = Best Regards, -Geoff/W5OMR __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] AM Amps
First you would need to tune it up at the 1500 watt out level. Then apply enough drive from the ranger so you have about 375 watts carrier out. That will be good for 100% modulation peaks. If you want to run more than 100% modulation then you would need to lower the carrier level with less drive. 73 Gary K4FMX Byron Lichtenwalner wrote: If you had an amp rated at 1500 pep rated for Continuous Commercial Service and were going to drive it with a Ranger, (with W3AM's modification as an example) where would you set the carrier level with no modulation? Byron, W3WKR __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] AM Amps
Geoff wrote: Gary Schafer wrote: First you would need to tune it up at the 1500 watt out level. Then apply enough drive from the ranger so you have about 375 watts carrier out. That will be good for 100% modulation peaks. Perhaps, if you were feeding nothing more than a sine wave to it. Do you wana think that one through again? :>) 73 Gary K4FMX
Re: [AMRadio] AM Amps
Geoff wrote: Gary Schafer wrote: I know full well that there is no such thing as a 375 watt carrier limit to AM power in the FCC rules. I never said there was. Ok, good. I was just making sure ;) Too many people believe that there's some 'magical mystification' about 375w of carrier output being the 'legal limit'. I was trying to "clarify" Ronnie's statement about how much power he runs his 813's at when he says he runs them at legal power out. And since we don't know if Ronnie has a symmetrical voice pattern or otherwise, we can only assume it is symmetrical when discussing general power principles. Maybe he has the peaks phased so maximum peaks are in the negative direction? I don't know. Either way it appears as though he only has enough headroom for less than 50% modulation in the positive direction. Agreed, there. And, I've been to Ronnie's shack. I'm pretty sure he doesnt' do any audio shaping, or phasing, or any other audio tricks on either the Ranger or the Globe King 500 he's running there. On top of that the plate dissipation is around 380 watts per tube if the amp is tuned properly, which it can't be if it is not burning up tubes. That is the whole point, if you are paying attention. :>) I was... it was just the 'legal limit' that caught my attention (yet again ;->) Maybe you could tell us how much peak envelope power would be available from a pair of GG 813's at 375 watts carrier out with 100% modulation? I'm not sure you can get more than around 1kW PEP output of a pair of 813's... and probably more like 800w. (3) in parallel would be a different story, though. 73 = Best Regards, -Geoff/W5OMR I would say you are pretty much on the mark there. I have a pair of 813's in GG also. I only run them at around 2500 volt and can get about 650 watts max out with 100 watts drive if I remember right. I ran them well over 3000 volts many years ago and got quite a bit more out of them but didn't have a decent watt meter then so I don't know exactly. 1000 watts out seems doable but they will be running around 1600 watts or more input. They will turn pretty red. Even on SSB at that power. 73 Gary K4FMX
Re: [AMRadio] AM Amps
Geoff wrote: I'm not sure you can get more than around 1kW PEP output of a pair of 813's... and probably more like 800w. (3) in parallel would be a different story, though. 73 = Best Regards, -Geoff/W5OMR I would say you are pretty much on the mark there. I have a pair of 813's in GG also. I only run them at around 2500 volt and can get about 650 watts max out with 100 watts drive if I remember right. I ran them well over 3000 volts many years ago and got quite a bit more out of them but didn't have a decent watt meter then so I don't know exactly. 1000 watts out seems doable but they will be running around 1600 watts or more input. They will turn pretty red. Even on SSB at that power. *whew* We agree on -something- ;-) But I'm enjoying the discussion. I may not be the most articulate individual around, and I'm -far- from reminding anyone of someone whom posses articulatino, but when it comes to someone saying "375w is the limit to run to get 1500w pep output", I can't swallow that. It's a true statement, if you were to apply a sine-wave (at an arbitrary rate... say, 1kc) to 100%, but as it's been said before, we don't -talk- in sine-waves. 73 = Best Regards, -Geoff/W5OMR But it is also true for voice modulation if you are talking about modulation peaks at 100% positive. Modulation is modulation. 73 Gary K4FMX
Re: [AMRadio] AM Amps
John, If you don't have any luck here try the Amps mailing list. Sure to find it there.[EMAIL PROTECTED] 73 Gary K4FMX John Coleman wrote: While on the Amplifier discussion, does any one know about a LK-800A by Amp Supply. It has 3 forced air cooled 800 watt plate dissipation, ceramic tubes, I think. It has some sort of a delay circuit to keep idiots from applying drive before the heaters or up to temp. This circuit has failed and now it doesn't ever allow keying. On the only schematic we have, there are no details about the timer delay circuit. It has a 555 timer and some other relays on a small circuit board. I'm hoping some one here has the needed info, else I have to reverse engineer the thing and will probably disable the stupid timer. John, WA5BXO __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] AM Amps
How do you reduce the drive for AM? I take it that is how you operate CW? 73 Gary K4FMX James M. Walker wrote: Hum, 4-1000A G.G. amplifier, 3000 VDC plate, 700 MA Plate I, 500 MA Grid I, with 125 Watts out of DX-100 running apprx 2100 W input and dissipating 670 watts plate = approximately 1430 watts output! While the carrier level into 50 ohm dummy load is 1400 watts measured and a really NICE orange glow! This is with a 200 cfm blower, air system socket and chimney. Jim WB2FCN - Original Message - From: "Jim candela" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Wednesday, January 12, 2005 7:07 PM Subject: RE: [AMRadio] AM Amps Darrell, That amp you built with the 4-1000 was a "killer" in more ways than one! Time for a confession.. Regards, Jim WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Darrell, WA5VGO Sent: Tuesday, January 11, 2005 6:04 PM To: Discussion of AM Radio Subject: Re: [AMRadio] AM Amps At 04:21 PM 1/11/2005 -0500, you wrote: In a message dated 1/11/05 12:14:43 PM, [EMAIL PROTECTED] writes: well all I can say is it works.. works well as a matter of fact, and has been for 6 years :) I typically run between 350 and 400 watts of carrier every day. It looks great on the scope. Modulation envelope is perfect. 100% modulation. In 6 years Ive only lost one tube, and I accidently broke that one. I have to agree with Gary. You're seeing 1600 watts PEP and 400W of carrier OUT with a pair of GG 813s??? Does not compute! Just curious, are you talking about 400W INPUT power to the linear under carrier only condx maybe? If so, this would work out to about 133W carrier OUT and each 813 dissipating about 133W which would make more sense. Dennis D. W7QHO Glendale, CA I'm with Dennis and Gary. To run a linear amplifier at 375 watts of carrier and 100% modulation, you will need around 800 watts of plate dissipation. For a short time a number of years ago, I tried running an AF-68 and a 4-1000A linear amplifier. I could never get more than around 450 watts of carrier and stay linearI didn't need a heater in the shack either. 73, Darrell, WA5VGO 73, Darrell, WA5VGO __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.6.10 - Release Date: 1/10/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.6.11 - Release Date: 1/12/2005 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] AM Amps
No, didn't mean it to be rhetorical. A legitimate question I thought. With some of the guys on here not quite understanding how to set up an amp properly for AM operation it didn't sound like you had yours set up properly if you were operating it like that on AM. Especially when you eluded that you only operated it at 1400 watts carrier into a dummy load. That would seem to indicate that you would expect peak power to be well over 1400 watts and into the illegal range. Which of course it would not be capable of. For AM operation with your setup the drive needs to be reduced to around 30 watts carrier after the amp is tuned up at the 1400 watt out level. Just wondering what method you use to reduce the DX100 output to 30 watts? 73 Gary K4FMX James M. Walker wrote: That's a rhetorical question right? Jim WB2FCN Gary Schafer wrote: How do you reduce the drive for AM? I take it that is how you operate CW? 73 Gary K4FMX James M. Walker wrote: Hum, 4-1000A G.G. amplifier, 3000 VDC plate, 700 MA Plate I, 500 MA Grid I, with 125 Watts out of DX-100 running apprx 2100 W input and dissipating 670 watts plate = approximately 1430 watts output! While the carrier level into 50 ohm dummy load is 1400 watts measured and a really NICE orange glow! This is with a 200 cfm blower, air system socket and chimney. Jim WB2FCN - Original Message - From: "Jim candela" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Wednesday, January 12, 2005 7:07 PM Subject: RE: [AMRadio] AM Amps Darrell, That amp you built with the 4-1000 was a "killer" in more ways than one! Time for a confession.. Regards, Jim WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Darrell, WA5VGO Sent: Tuesday, January 11, 2005 6:04 PM To: Discussion of AM Radio Subject: Re: [AMRadio] AM Amps At 04:21 PM 1/11/2005 -0500, you wrote: In a message dated 1/11/05 12:14:43 PM, [EMAIL PROTECTED] writes: well all I can say is it works.. works well as a matter of fact, and has been for 6 years :) I typically run between 350 and 400 watts of carrier every day. It looks great on the scope. Modulation envelope is perfect. 100% modulation. In 6 years Ive only lost one tube, and I accidently broke that one. I have to agree with Gary. You're seeing 1600 watts PEP and 400W of carrier OUT with a pair of GG 813s??? Does not compute! Just curious, are you talking about 400W INPUT power to the linear under carrier only condx maybe? If so, this would work out to about 133W carrier OUT and each 813 dissipating about 133W which would make more sense. Dennis D. W7QHO Glendale, CA I'm with Dennis and Gary. To run a linear amplifier at 375 watts of carrier and 100% modulation, you will need around 800 watts of plate dissipation. For a short time a number of years ago, I tried running an AF-68 and a 4-1000A linear amplifier. I could never get more than around 450 watts of carrier and stay linearI didn't need a heater in the shack either. 73, Darrell, WA5VGO 73, Darrell, WA5VGO __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.6.10 - Release Date: 1/10/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.6.11 - Release Date: 1/12/2005 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] AM Amps
3500 watts pep output would require a carrier of a maximum of 875 watts if it were 100% modulated. If the amp runs 65% efficiency at full output that means that the efficiency must drop to 1/2 that at carrier level or around 32% for proper AM operation. At 875 watts out with 32% efficiency would require an input power of 2734 watts for carrier. Subtract the 875 watts from that and you are left with about 1860 watts of plate dissipation power! That doesn't sound like any kind of CCS class B amplifier to me for a single 4-1000. Maybe a pair of 4-1000's? 73 Gary K4FMX James M. Walker wrote: In a properly designed and adjusted 4-1000A Class B amplifier, the approximate maximum power output in class "B" is 3.5 KW. That is CCS, and not ICAS. An amplifier of this output class was presented in a 195x Radio Engineers Handbook. The design works as the rig verifies, modes are AM/CW from the DX-100. Adjustments are left as an exercise for the student. Jim WB2FCN - Original Message - From: "Darrell, WA5VGO" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; "Discussion of AM Radio" Sent: Thursday, January 13, 2005 6:35 PM Subject: Re: [AMRadio] AM Amps Got to be CW, RTTY, etc. With AM you would either melt the tube down or splatter all over the band. 73, Darrell, WA5VGO At 04:49 PM 1/13/2005 -0500, you wrote: How do you reduce the drive for AM? I take it that is how you operate CW? 73 Gary K4FMX James M. Walker wrote: Hum, 4-1000A G.G. amplifier, 3000 VDC plate, 700 MA Plate I, 500 MA Grid I, with 125 Watts out of DX-100 running apprx 2100 W input and dissipating 670 watts plate = approximately 1430 watts output! While the carrier level into 50 ohm dummy load is 1400 watts measured and a really NICE orange glow! This is with a 200 cfm blower, air system socket and chimney. Jim WB2FCN __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] Space Bulliten
When did resonant antennas become a requirement for any type of operation? :>) 73 Gary K4FMX Geoff wrote: This will affect anyone operating on HF. Signals need good, proper, resonant antennas. After antenna, is power. Not a lot of power is needed, if you've got a good working antenna. But it's all for naught, if there's no propagation. 73 = Best Regards, -Geoff/W5OMR - Subject: Space-Weather-Bulletin Official Space Weather Advisory issued by NOAA Space Environment Center Boulder, Colorado, USA SPACE WEATHER ADVISORY BULLETIN #05-1 2005 January 14 at 03:51 p.m. MST (2005 January 14 2251 UTC) RAPIDLY GROWING SUNSPOT REGION <>On 10 January, a new sunspot group emerged and was assigned NOAA Region number 720. This sunspot group has grown rapidly and currently has an area of 1540 millionths of the size of the Solar disk (about 18 times the size of the Earth). So far this region has only produced minor flare activity (R1). However, its growth and complexity suggest that it is capable of moderate to strong levels of flare activity (R2 to R3 levels) during the next 7 days. . <> These types of flares lead to HF radio blackouts. The effects range from minor degradation of HF communication (R1), up to wide area blackouts on the daylit side of the earth for about an hour (R3). Data used to provide space weather services are contributed by NOAA, USAF, NASA, NSF, USGS, the International Space Environment Services and other observatories, universities, and institutions. For more information, including email services, see SEC's Space Weather Advisories Web site http://sec.noaa.gov/advisories or (303) 497-5127. __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] Physical Reality of Sidebands
Donald Chester wrote: From the beginnings of radiotelephony there has been a question whether sidebands exist as physical reality or only in the mathematics of modulation theory. Don, That is a question that can keep you up nights trying to visualize! The sidebands do exist in reality but not because of the way we may receive them or detect them. re narrow ringing filters in the receiver. The carrier also exists constantly with modulation but the reasoning tends to get a little fuzzy as the modulation frequency gets lower as you note. I don't believe that the carrier still exists because of tank circuit ringing when 100% negative modulation is reached either. The Q of the tank only allows for a couple of cycles at most when no carrier is present. It decays very quickly. With modulation, even at voice frequencies, the modulation frequencies are much lower and there are many more rf cycles for each audio cycle. So one audio cycle would be equivalent to many rf. Modulation is a multiplication process not one of adding audio to the carrier. Even though it works out the same when you add and subtract the modulating frequency to the carrier to figure where the side bands are. They don't get there by the addition / subtraction process but by the multiplication process. When looking at a signal with a spectrum analyzer you are looking in the frequency domain. When looking at a monitor scope you are looking in the time domain. When the modulating frequency gets very low it is hard to detect the side bands as you have noted. With very low frequencies as you describe, the carrier being off for 6 months and on again for 6 months, gets into how you are referencing it. Your reference must also be very long in order to still be in the frequency domain. The frequency domain and time domain kind of merge as I gather it. That is how it was explained to me. I am still kind of fuzzy on the issue though when it comes to low modulating frequencies as you describe. Another thought on the subject is to look at the opposite of what you describe. When mixing frequencies against a local oscillator to create a new frequency, you have the same modulation process taking place. You can look at the carrier, as it is usually way far away in frequency from the mixing signal, and it will appear the same when the mixing signal is present or not. You can in no way distinguish the difference. Good subject. 73 Gary K4FMX
Re: [AMRadio] Physical Reality of Sidebands
Bob Bruhns wrote: Indeed, 'tis a puzzlement. I can draw three continuous sine waves of apppropriate amplitude, frequency and phase, corresponding to carrier, upper sideband and lower sideband, and I can add them point by point, and I can duplicate a 100% modulated AM signal waveform as we understand it. I have to believe that this works backwards; if I make this waveform by modulating a carrier in an AM transmitter, then I am synthesizing the same continuous sine waves. Hi Bob, The three sin waves look like what is happening but in reality the am signal is not produced by adding sin waves. It is produced by multiplying them. It just happens that when you add them you come out with the same result so it appears that they are added. And to keep things simple that is how it has been taught over the years as another poster mentioned. 73 Gary K4FMX
Re: [AMRadio] Physical Reality of Sidebands
Jim Wilhite wrote: Out of curiosity Gary, where do you think the multiplication occurs? In the plate of the final(s), at the juncture of the plate and output network, or in the final network? I have pondered this one and have an opinion, but would like yours and others opinions. 73 Jim W5JO Hi Jim, I should have figured you would come up with that one. :>) In an oscillator it is really the tuned circuit that is the oscillator and the tube is just a switch that keeps the oscillation going in the tank. Same for the output tank on an amplifier. The tube is a switch that excites the tank. However with modulation you can do it with a diode and a resistor for the load so I would have to say that modulation takes place as a function of the switch action. But without the load there is no current so nothing happens. So it seems it may occur at the junction of the load and the switch? 73 Gary K4FMX
Re: [AMRadio] Stagger Tuning IF transformers with scope
Hi Scott, To do it with the scope you need a sweep generator synced with the scope horizontal trace. Then hook the scope vertical to the output of the IF stage. It is difficult to do without some sort of marker generator for the two frequencies you want for the bandwidth. You could use one signal generator and move it to each band edge and put a mark on the scope screen. Another way to stagger tune the IF is with just a signal generator and the S meter on the receiver. Assuming the receiver has good dial calibration of 1khz or better. Actually you don't even need a signal generator. You can use the crystal calibrator for the signal source. Tune in the calibrator signal and find the center of the band pass by maximum signal strength. Note that frequency on the dial. Now tune to one side and see what frequency where the S meter drops about 1 S unit. Do the same in the other direction. Add the two differences together and that is how wide the If is now. To widen it, tune to where you want the new band edge on one side. Now tune one of the IF cans to get a peak at that frequency. Move the dial to the other side of the signal by the same amount frequency wise and tune a different IF can for a peak there. Note that the total signal will be down some from when you started and the S meter will not read as high as originally. Repeat these same steps with other IF cans. Then recheck where the 1 S unit down points are on both sides of the signal. Also see that the difference comes out to the frequency where the middle should be. Sometimes it is easier to stagger the two coils in each can. Tune one high and one low. Do this a little at a time and recheck your 1 s unit down points often. That will give you an idea of the progress. When done tune across the signal and watch the S meter for "ripple". You will see it go up and down an S unit or so when tuning from one side to the other. You don't want to get too much ripple in there or it will cause distortion. You can play with the tuning a little to smooth out the ripple. Once you get the feel for how much things change you can do a pretty good job usually. Sometimes you run low on gain. Some receivers have such sharp IF cans that you can not get rid of the ripple when staggering them very far without loosing a lot of gain. 73 Gary K4FMX [EMAIL PROTECTED] wrote: It's embarrassing to ask, but I want to stagger tune the IF transformers in a 51J for a little broader AM response with my scope, and realized I don't know exactly what to do - I assume you use a sweep generator or FM sig wider than the bandpass, but don't understand how to use the scope to look at the response (and to think I got my license when you had to know something) - if there's a reference on line somewhere or someone can give me a hint I'd really appreciate it. Thanks, Scott __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
amradio@mailman.qth.net
Hi Ronnie, I repaired one awhile back. I glued on some new plastic strips with 2 part epoxy and it held fine. Leave the old strips on as much as you can to hold the coil together and place the new strips over the old. Peal off the loose stuff. If there is enough of the old that is in place but a little loose just epoxy it back in place. Yes there was another coil that they made with all tubing. It was for lower plate impedance tubes like a 4cx1000. The one with part tubing and part wire is for higher impedance tubes. I can't remember the part number of the other one. 73 Gary K4FMX ronnie.hull wrote: I have just become the proud father of a nearly mint b&w850A. From storage however, the plastic strips that support the front of the inductor, have warped somewhat. Any suggestions about fixing this, from those of you who have faced this same problem, would be greatly appreciated. On the subject of B&W Inductors, am I crazy, or, wasn't there a inductor/switch set that was similiar to the 850A but was solid tubing? cornfuzzed minds want to know :) 73's Ronnie - W5SUM __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] Old Novice Days
Geoff wrote: Bill Connelly wrote: Thank you! Bill, W3MJ At 12:09 PM 2/23/2005 -0600, you wrote: Bob Macklin wrote: <>In 1969 the 40M Novice segment was 7150 - 7200. In 1986 it was 7100 - 7150. Bob Macklin K5MYJ/7 Seattle, Wa. Before that. I got my ticket in Feb of 1984, and it was 7100 to 7200kcs Hold off on the thanks... after I read and re-read that, something didn't look correct... Let me try again, with these statements that I know (to the best of -my- current education) to be fact... I do not ever, at anytime, remember the Novice CW sub-band of 40m , being more than 50kc wide. I've always known the Novice CW sub-band of 40m to be from 7100 to 7150kc. There. That's what Ive been -meaning- to say and/or stick with. I, personally, don't ever remember the Novice band on 40m being as high as 7200kc -- 73 = Best Regards, -Geoff/W5OMR Geoff, I think you are right about it being only 50kc wide. I don't know when they changed but in the early 60's it was from 7150 to 7200. My one and only crystal then was 7175 kc. You young kids probably don't remember that. :>) 73 Gary K4FMX
[AMRadio] SSB AM revisited
SSB AM has been discussed before and was always thought the transmitter to have audio power down 3 db from regular double side band AM transmitter. This is because of only transmitting one side band and thus half the power in the side bands. A DSB AM transmitter has each side band 6 db down from the carrier. In thinking about it I was trying to come up with how we get the same PEP power with SSB AM as we do with DSB AM. It turns out that you can run 4 times the side band power in a single side band as you can when using double side band AM. With SSB AM 100% modulation the side band power equals the carrier power! It is not 6 db down as each side band is with DSB AM. If you look at PEP with AM, the voltage into the antenna doubles with modulation to make PEP 4 times what the carrier power is. With SSB AM the voltage also doubles to make PEP 4 times carrier power. But in this case it takes the same amount of power in the side band as there is in the carrier! Just to verify all this I hooked up the spectrum analyzer, scope and PEP watt meter to the old 20A. Here is how the numbers work out: On AM DSB. carrier power= 2 watts. carrier volts= 10 volts. side band power each = .5 watts. side band volts each = 5 volts. PEP of transmitter =8 watts. On SSB AM. carrier power = 2 watts. carrier volts = 10 volts. side band power = 2 watts. side band volts = 10 volts. PEP of transmitter =8 watts. When figuring PEP of an AM transmitter you must add the voltage of each component together and then square it and divide by the resistance it feeds. You can not add power directly. In the case of DSB AM the voltage of the carrier gets added plus the voltage of the upper side band plus the voltage of the lower side band. In the example above that equals 20 volts. 20x20=400. divide by 50 = 8 watts PEP. With SSB AM there is only the carrier and one side bands voltage to add together to find PEP. In the above example 10 volts carrier plus 10 volts side band = 20 volts. Squared= 400 divide by 50 = 8 watts PEP. But as you can see there is twice the voltage in the side band or 4 times more power in it than with double side band am. This still gives the same PEP. With 6 db more audio power in SSB AM than in one side band of DSB AM the recovered audio should be the same as with DSB AM. DSB AM was always thought to have a 6 db advantage because of having the second side band and being coherent in the detector. Seems this evens things out. Of course there are the distortion issues in the detector with SSB AM to deal with. With a little thinking you can see where you might be able to run more carrier power with SSB AM and not having to reduce the audio level as much as you would with DSB AM and have the PEP still stay within limits. Here are some numbers with the carrier increased to 3.34 watts (1.67 times) and audio down only by 3 db. carrier power= 3.34 watts. carrier volts= 12.93 volts. side band power = 1 watt. side band volts = 7.07 volts. PEP of transmitter =8 watts. 73 Gary K4FMX
Re: [AMRadio] Power Resistor
Jim, I have repaired those resistors by putting a clamp over the burned out spot. Usually works fine. 73 Gary K4FMX Jim Wilhite wrote: No minimum order required and no handling charge either. In the past, if they did not have the item in stock and had to ship some part later, they didn't charge shipping on the second package unless the high price of fuel has changed things. Good people to do business with. The problem with series (say 2 - 10k ) is mounting. Not enough room. Thanks for the suggestion Jim. 73 Jim W5JO - Original Message - From: "Donald Chester" <[EMAIL PROTECTED]> To: Sent: Sunday, March 20, 2005 2:41 AM Subject: RE: [AMRadio] Power Resistor Try Mouser at www.mouser.com or at http://www.mouser.com/catalog/621/437.pdf They have 10K, and 25K at 25 watts or 50 watts adjuatable. Maybe get a 10K fixed at 25 watt, and series with another 10K at 25 watt adjustable. If you can tolerate 25K this is a one piece solution for $11.61 + .29 twice for mounting ears. mouser is a Fast shipper! Do they require a minimum order for shipment? Don K4KYV __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
[AMRadio] K4KYV monitor scope
Don, If you are around, some time ago there was a discussion where you described what you did to your heath kit monitor scope to reduce the hum on the trace. I am working on mine and can't recall what all you did. Thanks Gary K4FMX
Re: [AMRadio] K4KYV monitor scope
Donald Chester wrote: If you are around, some time ago there was a discussion where you described what you did to your heath kit monitor scope to reduce the hum on the trace. I would have to dig up the documentation, but relying on my memory, I recall beefing up the HV filtering, rerouting the filament circuitry and replacing the magnetic shield on the scope tube. As I recall, I substituted a separate filament line for the original design that depended on the chassis for one side of the circuit. The piece of tin wrapped around the neck of the tube is worthless is a magnetic shield. I had an old military RTTY monitor that used a similar shaped scope tube, and cannibalised the special black anodised magnetic shield and managed to shoehorn it in place by relocating some of the original scope components. I got rid of most of the hum that shows up on the vertical trace, and the additional filtering got rid of the hum that modulated the brightness of the trace. I also modified it to add some astigmatism control, which results in a sharper, better focused and better defined image. The original designers could have done a much better job. The manual even mentions the problem; they pass it off as "insignificent" in a scope that is "only" designed to monitor modulation. Since I use mine only on AM, I pulled out the tube from the two-tone generator and vertical amplifier. That lightens the load on the failure-prone power transformer. I excite the vertical deflection plates directly with rf. Instead of running the rf feedline through the scope, I use a remote toroidal pickup link to feed the scope some distance away from the rf feedline. I had to locate it on the transmitter side of the antenna relay; otherwise the pickup link was inducing an intolerable level of noise from the scope into the receiver. Don K4KYV Thanks Don! Now I need to find some 1600 volt caps for the high voltage. I thought I knew where to get them but can't seem to find them now. Anyone have any idea? .15 mfd or greater at 1600 volts. Thanks Gary K4FMX
Re: [AMRadio] AF-68
Just a note about the supply Geoff, if it is the ac/dc supply be careful if you run it on dc. Most all of theme came from the factory setup for 6 volts! You will cook it if you run it on 12 volts and don't rewire it for 12 first. AC is ok either way. 73 Gary k4FMX Geoff wrote: I have one of these beauties. I am also now the proud owner of an AC/DC power supply from Multi. What I do NOT have is the connecting cable. Does anyone have one? thanks! 73 = Best Regards, -Geoff/W5OMR (/5 New Orleans, LA) __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] power ratings
[EMAIL PROTECTED] wrote: I have a junker HW-100 with a good PA section. How much power could I run as a linear amp using 2X6146 and what rating power supply would I need? Thanks. Ed K6UUZ 25 watts carrier with 100 watts pep output on the 6146's. 73 Gary K4FMX
Re: [AMRadio] power ratings
The best quality audio of all can be gotten from low level modulation and a linear amplifier. 73 Gary K4FMX Bob Macklin wrote: A comment about AM transmitters. A plate modulated AM transmitter requires a modulator of 50% of the power of the final to produce 100% modulation. These transmitters like the Johnson Ranger produce better audo than the screen modulation units like the small Heaths. Only the Heath DX-100 and TX-1 (Apachee) used plate modulation. But most of the airborne military transmitters used screen modulation to reduce the weight and power requirment. These all produce very good comunication audio. But if you want broadcast quality audio you need a real plate modulated rig. Bob Macklin K5MYJ/7 Seattle, Wa. "REAL RADIOS GLOW IN THE DARK" - Original Message - From: "kenw2dtc" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Tuesday, July 12, 2005 5:30 PM Subject: Re: [AMRadio] power ratings "Ken, as I read the rules, we are only allowed to run 375 watts carrier. With 100% modulation this will give us 1500 watts pep which is the max output allowed." ***Don, You are correct about the 1500 watts PEP. It could also be derived by 600 watts of carrier with much less than 100% modulation. There are also schemes where the carrier is almost 1000 watts and it is modulated downward at nearly 100% and still get the 1500 watts PEP. Another comment about linears in AM service. Those who do the math and run an SSB linear with the PEP equal to 4 times the carrier sometimes miss the calculation of the male voice which will usually modulate higher than 100% unless limited in the audio section. Thus many SSB amps do not have the headroom for good AM. __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] power ratings
kenw2dtc wrote: "But if you want broadcast quality audio you need a real plate modulated rig" "The best quality audio of all can be gotten from low level modulation and a linear amplifier." ***I disagree with both statements above. If properly set up and fixed with the proper audio chain, a plate modulated rig, a broadcast transmitter, a rice box and linear, a plate modulated rig and a linear or a class "E" rig could sound like "broadcast quality" and the listener would not be able to distinguish the difference. 73, Ken W2DTC But the difference could be measured. 73 Gary K4FMX
Re: [AMRadio] power ratings
Geoff wrote: Gary Schafer wrote: The best quality audio of all can be gotten from low level modulation and a linear amplifier. 73 Gary K4FMX However, highly non-efficient. --- 73 = Best Regards, -Geoff/W5OMR Efficiency doesn't matter anymore for hams. Output power is the limiting factor not input power. 73 Gary K4FMX
Re: [AMRadio] power ratings
Geoff wrote: Donald Chester wrote: The plate dissipation of the 6146's is the key. Your carrier steady on should not exceed the dissipation rating. This is about 50 watts if I remember right which would give you 200 watts PEP. So your power suppl;y should be capable of about 150 watts continuous and it will handle the 200 watts on peaks. I would beef up the fan so that I had a good amount of air passing the glass of the 6146's to keep the seals cool. In AM linear service, the carrier output should not exceed HALF the total plate dissipation. A 6146 runs about 25 watts plate dissipation, so with a pair of them, you should be able to run 25 watts out. With 100% modulation in the positive direction, that would be 100 watts pep. A properly functioning AM final capable of 100% modulation should run about 33% carrier efficiency. That means that two-thirds of the input power is dissipated in the plates of the final, and one third is delivered as rf output. When the carrier is modulated, the final actually becomes more efficient, so the plate dissipation is reduced under modulated conditions. The DC input should not vary, so that simply means that some of the DC input that was being dissipated as heat is now being converted to rf output in the form of sideband power. Is that where sideband energy then is created and therefore exists as long as there's a modulate AM carrier? I wasn't in on the big discussion about this, a few months ago. --- 73 = Best Regards, -Geoff/W5OMR The side band power is created in the low level modulated stage and amplified by the linear amp just like the carrier. However, the total amplifier power operates on the composite signal and not individually on each component of the signal. The composite signal looks like one signal to the amplifier. With modulation present the amplifier is operating at a better plate impedance match to the load at that power level. With modulation peaks it is operating at the load point where it was tuned to, its most efficient point. So as modulation increases the load point of the (properly tuned) amplifier has a better match and delivers more power out at that higher power level (modulation peaks). The efficiency of the amplifier increases as load point is approached. You can readily see how the efficiency changes with power level by varying the carrier drive level (no modulation) and calculating input power verses output power at different drive levels. For more insight look at "efficiency modulation" in some of the handbooks. 73 Gary K4FMX
Re: [AMRadio] power ratings
Donald Chester wrote: Gary K4FMX said: The best quality audio of all can be gotten from low level modulation and a linear amplifier. A linear amplifier has the same kind of distortion as a class-B modulator. That's true except with a linear amp most of the distortion products fall outside the audio bandwidth. 2nd and third harmonics etc. are outside the audio bandwidth. With tubes, the best quality audio can be had from low distortion plate modulators such as class-A series or Heising modulation, or pushpull plate modulators running class A or AB1. Except for the distortion introduced by the modulation transformer. Pulse-width series modulators produce perhaps the best audio. I suspect the best quality of all comes from the new class-E rigs. Agreed. According to the tube manuals, class-B audio service has inherent distortion levels on the order of 3-5%. It can be reduced with negative feedback. My Gates BC1-T manual claims less than 2% distortion at 100% modulation. The signal driving a linear amplifier has its own distortion, since the original signal has to be produced somehow. Pushpull class-A audio or series modulation, with feedback, might be a good candidate for the driver stage of a linear. If the linear is run properly in class AB1, that would be near the best possible audio out of a tube transmitter, even though the efficiency is not all that good. With low level modulation and a linear amp it is much easier to produce excellent audio than it is from high level plate modulation. Building a low power (driver) low distortion AM transmitter has fewer problems than high power low distortion transmitters. Class A direct coupled modulation schemes can be accomplished much easier at low levels than at high levels. Use of a balanced modulator can also eliminate the problems associated with occasional over modulation that plagues high level conventional modulation. Speaking of efficiency, an AM linear or grid modulated amplifier has close to the same overall efficiency as plate modulation, when calculated from the ratio of power drawn from the a.c. mains, to rf carrier output. A linear amplifier running AM has exactly the same efficiency as when it runs SSB. It's just that the duty cycle is different. That's true. An SSB amplifier at a power output level of 1/4 its full power has an efficiency level of exactly 50% of its full power out efficiency. If it is 66% efficient at full output it will be 33% efficient at 1/4 power output level. Just like it is with an AM signal as you say. Actually, since with the human voice, the average power is 7-8 dB lower than peak power (equivalent to around 30% modulation), the average efficiency of a SSB linear is similar to that of an AM linear because the efficiency of a linear is a function of the amplitude of the signal (0% at idling current, and a maximum of about 67% at maximum peak output just below the point of saturation or flat-topping). AM linears got their reputation as "low efficiency" on AM because of the 100% duty cycle carrier runs about 30% efficiency to allow enough headroom for the positive peaks. With an AM linear, you can see the glow on the plates DECREASE when you whistle into the mic to produce 100% tone modulation. The DC input is the same regardless of modulation, but the rf output is higher, since sideband energy is now included. That power has to come from somewhere, so the efficiency of the amplifier goes up to generate the sidebands. The advantage of plate modulation with AM is the ease of tuning up and QSY'ing. You simply dip the final and load to the desired carrier output, while maintaining enough grid drive to assure class-C service. With low-level modulation (linear or grid modulated), the rf drive level and degree of antenna coupling are critical to the modulation linearity of the final. With a rice box type exciter and amp for low level modulation all one has to do is turn the knob to insert full drive, tune both final and load controls for maximum output and then reduce drive to 25% of full output and you are good to go. 73 Gary K4FMX
Re: [AMRadio] A bit of Viking Valiant help
I agree with Jim. I would check to see that the clamp tube adjustment is set correct first. Sounds like you don't have enough drive and the clamp tube is not cutting off the screens. 73 Gary K4FMX Jim candela wrote: John, I am not a Valiant owner, but you sure seem to have a annoying and expensive problem. I keep thinking that your DC operating point is wrong somehow. Since the finals are class C, there should be enough bias to completely cut off the finals in the absence of drive. Maybe try this on CW mode and see what the key up cathode current is. I think it should be zero milliamps. Today's line voltage is typically higher than back in the 50-60's, so spec bias may not be enough today. Got a Variac? What is your filament voltage? Seven volts is too high. Also the screen voltage might be a little high too. I'd concentrate looking at this in CW mode, and Linear SSB mode. I seem to recall that a Valiant has some kind of switch to allow a SSB adapter to drive it and the 6146's run in linear mode. If you have no cathode current in CW key up, and linear mode is idling fine without a rising cathode current over time, then the tubes, and DC parameters are not the problem. I suspect however that you will have trouble with these tests, and the problem is seen static, in the absence of RF drive. I might be wrong, so read on. If the problem is seen with drive, and on the lower frequencies as you mention, then think that the RF plate load impedance is wrong, and tube efficiency is so poor that they get hotter and hotter by the second, and go into a thermal runaway. I see this problem when trying to make a poor 6DQ5 work on 6 meters in my Gonset G-76. No can do, 6 meters on a G-76 is a joke. I am not sure what a Valiant can do, but my guess is that 200 watts DC input on AM should give you about 150 watts RF output (150/200 * 100 = 75%). A 6146 normally should not show any color in the plate. Are yours blushing? If the RF plate impedance is wrong, and efficiency is poor, then it's time to scrutinize that pi-network for problems. Some of the loading capacitors may have gone south, and are only used on the lower frequencies. If you suspect a VHF parasitic oscillation, look for sudden jumps in grid current , or cathode current while adjusting the controls for plate and grid tuning. Also a neon bulb near the plate of a 6146 (can mount to a pop sickle stick) should glow orange. The color turns more purple at VHF. Keep in mind that this is general advice, and that others with more first hand Valiant experience may nail this with one stab instead of me with my buck shot approach. Hope this helps. Why would this be: "It is my understanding that sometimes subbing in the "'B" for the early 6146 just doesn't cut the mustard." Could it be that we need to adjust the DC parameters for the 'B' like lowering the screen voltage a little, or a little more fixed grid bias? Or is this tube unsuitable for use in a Valiant for some other reason? The 'B' was used a lot in AB1 liner use with plate voltages up to 1000 volts. Maybe the 'B' is not tame in a Valiant, and wants to go into a destructive VHF parasitic oscillation often enough to make us curse them? Regards, Jim Candela WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of GBrown Sent: Saturday, August 27, 2005 1:01 PM To: Discussion of AM Radio Subject: Re: [AMRadio] A bit of Viking Valiant help Just a wild a-- guess, but I thought that the Valiant used only 6146's, not the "B" 6146. It is my understanding that sometimes subbing in the "'B" for the early 6146 just doesn't cut the mustard. Regards, Gary...WZ1M - Original Message - From: "John Lawson" <[EMAIL PROTECTED]> To: Sent: Saturday, August 27, 2005 1:56 PM Subject: [AMRadio] A bit of Viking Valiant help I'm in the middle of a long, slow project to get my Valiant back in service. I've changed out the bigger power tubes, solid-state replacements for the 866s, and partially re-capped the rig, specifically the RF power section. After finding (expensively) out that 'W' 6146s just don't work, I replaced the finals with new 'B's and power is now being transferred to the antenna / dummy load. Main bug: On the bands below 20M, however, and getting 'worse' as the frequency gets lower, the rig "runs away" after 15 - 30 seconds - the plate current rises fatser and faster and then needs to be shut down, lest another set of 6146s gets wasted. ;} I have neutralized the transmitter per the manual, seems ok. Bias also set per sepc. LV rectifier tubes have been chacked (on a Weston 686) and seem within spec, though their performance under load is measurable only in situ. I left the doorknob cap alone because it's fine electrically and not cracked or discolored. Do the sypmtoms sound familiar to anyone? Before I spend a bunch more hours wearing out the transmit switch, I thought I'd ask those who have a lot more experience than I
Re: [AMRadio] Linear Efficiency on AM
With an AM linear the efficiency at carrier must be / will be exactly one half what it is at PEP. Provided it is tuned properly. 73 Gary K4FMX John E. Coleman (ARS WA5BXO) wrote: I would say that is about right Brian. There has been some discussion about this here in the past. It has been shown that in some cases the efficiency actually is less at carrier level and goes up to 35% with modulation when working properly. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, September 28, 2005 5:06 AM To: Discussion of AM Radio Subject: RE: [AMRadio] Pi-Net vs Link Couple ON another group they claim that you can get AT BEST 35% efficiency with AM LInear mode with ANY class linear amplifier. __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami
Re: [AMRadio] GG 813 Linear in GE Ham News
A pair of 813s in GG are only good for 150 watts carrier out on AM. 73 Gary K4FMX [EMAIL PROTECTED] wrote: Hello All, The thread on final circuits has been great to follow especially with the mention of 813's. It is still a very cost effective tube and in good supply NOS since the audio crowd has yet to make much use of them. I have a copy of GE Ham News from Nov-Dec 1959 that features a "Kilowatt Grounded-Grid Linear Amplifier" to quote the cover. It uses a pair of 813s GG with a standard Pi Net output configuration 5 band switched 80 -10 mtrs. Looks real easy to build and with the exception of the B&W filament choke FC-15, I have most of the needed parts or can find them. The construction article is well documented and pictured. Is anyone is familiar with this amplifier or better yet knows of one being built? If 160 meters would be easy to extend to with more L & C where needed then it would work well for anyone with a good drive source. For those that do not have the Ham News Issue I can scan a copy and e-mail it. Thanks for any info, Bill KB3DKS/1 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami
Re: [AMRadio] GG 813 Linear in GE Ham News
W5OMR/Geoff wrote: Gary Schafer wrote: A pair of 813s in GG are only good for 150 watts carrier out on AM. 73 Gary K4FMX I'm not trying to start anything here, Gary, but that statement seems to be in stark contrast to what you said, yesterday... With an AM linear the efficiency at carrier must be / will be exactly one half what it is at PEP. Provided it is tuned properly. 73 Gary K4FMX What would the efficiency be of an AM Linear at carrier. (or maybe I'm not reading this correctly, because I've yet to have coffee this morning, and I -know- I probably should'n't be posting messages in this state... ;-)) -- 73 = Best Regards, -Geoff/W5OMR Hi Geoff, Yes both statements are true. Remember that the PEP is 4 times the carrier power with a 100% modulated AM signal. A pair of 813s are good for about 600 watts PEP output. So that limits carrier power to 150 watts if 100% modulation is used. You can squeeze a little more power out of the 813s but they start to turn a little red. I have had a pair of 813s in grounded grid that I built about 30 years ago. Tough tubes. The "efficiency at carrier" that I was referring to is the efficiency of the amplifier at the power level that the carrier runs when any amplifier is set up for AM operation. Like the 813s, 600 watts PEP out requires that the carrier be operated at 150 watts output. If the amplifier has say 60% efficiency at the full PEP level then at 1/4 the power output the efficiency will be 1/2 of what it was at full power or 30% in this case. This is not only true for AM operation but for SSB operation as well. As long as the amplifier is to remain linear this efficiency ratio must exist. (see Orr's radio handbook. see "efficiency modulation") If that efficiency ratio is not maintained then the amplifier is not operating linearly. If you readjust the loading at carrier level to increase the power then it will no longer be linear when the modulation is applied. 73 Gary K4FMX
Re: [AMRadio] Linear Efficiency on AM
Hi Eddy, Yes that is also a good rule. 73 Gary K4FMX [EMAIL PROTECTED] wrote: Gary... Look at the tube charts for the tube(s) you are planning to use, take note of the plate dissipation...your carrier output should be HALF of that figure for safe use as an AM linear. ~73~ Eddy VE3CUI - VE3XZ With an AM linear the efficiency at carrier must be / will be exactly one half what it is at PEP. Provided it is tuned properly. 73 Gary K4FMX John E. Coleman (ARS WA5BXO) wrote: I would say that is about right Brian. There has been some discussion about this here in the past. It has been shown that in some cases the efficiency actually is less at carrier level and goes up to 35% with modulation when working properly. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, September 28, 2005 5:06 AM To: Discussion of AM Radio Subject: RE: [AMRadio] Pi-Net vs Link Couple ON another group they claim that you can get AT BEST 35% efficiency with AM LInear mode with ANY class linear amplifier. __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami
Re: [AMRadio] GG 813 Linear in GE Ham News
Hi Jim, No magic in the 600L. If you run it at 100 watts carrier out then it has to be capable of 400 watts PEP output in order to be linear. That would be around 660 watts input. Assuming 60% efficiency in AB2 grid driven. At the 100 watt carrier level the efficiency would be around 30% so input power would be about 333 watts. Plate dissipation would be 233 watts! 813s will tolerate that for awhile. But I don't think the 600L will put out 400 watts PEP? At least not while being linear. You may be able to see that much out of it at tune up if driven hard but I would bet it gets driven closer to class C with that much power out. 73 Gary K4FMX Jim candela wrote: Gary, Yes your correct. That said a 813 has conservative Pd rating of 125 watts whereas tubes like the 572 which appear similar in plate area are rated for 160 watts Pd. The rule of thumb is for AM use is that the max carrier output is 1/2 the Pd of the tube(s) + feedthrough power (G-G circuit), so for two 813's we have (125 + 125)/2 + 25 (guess) = 150. This assumes an efficiency that is about 33% carrier alone, and 66% at 100% sine wave modulation. I bet we can get closer to 200 watts out for ICAS service and still have headroom for 100% modulation from a pair of 813's. Those tubes better be forced air cooled, and you better be talking without pause since the tubes will cool down with modulation (efficiency doubles at 100% sine wave modulation). This rule of thumb doesn't seem to apply to my Central electronics 600L linear which has a one 813 grid driven in AB2 mode. This amplifier can put out 100 watts carrier and modulate it fully to + 100%. This implies the tube is dumping 200 watts (no modulation) for 100 watts output. There is color in the tube for sure, but 200 watts? I don't think so. Maybe those broadband couplers in the patented 600L somehow boost the efficiency. I have never figured out why the 600L can do that. Jim WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Gary Schafer Sent: Wednesday, September 28, 2005 9:24 PM To: Discussion of AM Radio Subject: Re: [AMRadio] GG 813 Linear in GE Ham News A pair of 813s in GG are only good for 150 watts carrier out on AM. 73 Gary K4FMX [EMAIL PROTECTED] wrote: Hello All, The thread on final circuits has been great to follow especially with the mention of 813's. It is still a very cost effective tube and in good supply NOS since the audio crowd has yet to make much use of them. I have a copy of GE Ham News from Nov-Dec 1959 that features a "Kilowatt Grounded-Grid Linear Amplifier" to quote the cover. It uses a pair of 813s GG with a standard Pi Net output configuration 5 band switched 80 -10 mtrs. Looks real easy to build and with the exception of the B&W filament choke FC-15, I have most of the needed parts or can find them. The construction article is well documented and pictured. Is anyone is familiar with this amplifier or better yet knows of one being built? If 160 meters would be easy to extend to with more L & C where needed then it would work well for anyone with a good drive source. For those that do not have the Ham News Issue I can scan a copy and e-mail it. Thanks for any info, Bill KB3DKS/1 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.8/114 - Release Date: 9/28/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.8/114 - Release Date: 9/28/2005
Re: [AMRadio] GG 813 Linear in GE Ham News
W5OMR/Geoff wrote: Hi Geoff, Yes both statements are true. Remember that the PEP is 4 times the carrier power with a 100% modulated AM signal. if it's modulated with a sine-wave, that's a true statement. A pair of 813s are good for about 600 watts PEP output. So that limits carrier power to 150 watts if 100% modulation is used. I understand that, but in a grounded grid arrangement, as it's already been said here, there's the exciter drive power that's added to the signal. So, in order for there to be 100% modulation, you must modulate the exciter, as well. The "efficiency at carrier" that I was referring to is the efficiency of the amplifier at the power level that the carrier runs when any amplifier is set up for AM operation. Like the 813s, 600 watts PEP out requires that the carrier be operated at 150 watts output. Thereabouts. Again, if you're modulating it with a sine-wave, then it holds true that 100% modulation is 4x the carrier output. However, we don't speak in sinewaves, as John/WA5BXO, Don/K4KYV and Bob(Bacon)/WA3WDR have so eloquently stated in http://w5omr.shacknet.nu:81/~wa5bxo/asyam/Amplitude%20Modulation.htm If the amplifier has say 60% efficiency at the full PEP level then at 1/4 the power output the efficiency will be 1/2 of what it was at full power or 30% in this case. This is not only true for AM operation but for SSB operation as well. As long as the amplifier is to remain linear this efficiency ratio must exist. (see Orr's radio handbook. see "efficiency modulation") If that efficiency ratio is not maintained then the amplifier is not operating linearly. If you readjust the loading at carrier level to increase the power then it will no longer be linear when the modulation is applied. Which, to me, would be another good reason why you shouldn't plate-modulate a grounded-grid (aka 'linear') amplifier. -- 73 = Best Regards, -Geoff/W5OMR Geoff, I am ONLY talking about a linear amplifier here. The drive signal is already modulated. If you are modulating the final stage these efficiency rules discussed here do not apply. Unless you would be talking about grid modulation and then they "do apply". It does not matter what type of signal is modulating the signal when the linear amp is involved. Whether it is a sine wave or speech or anything else. The PEP rule still applies for 100% modulation! You can not exceed 100% positive peak modulation if the carrier is set at any level greater than 1/4 the PEP output capability of the amplifier. Unless you want to operate it in a non linear mode. 73 Gary K4FMX
Re: [AMRadio] GG 813 Linear in GE Ham News
You got it Geoff!! :>) 73 Gary K4FMX W5OMR/Geoff wrote: Gary Schafer wrote: See? I -knew- I was getting muddled again. (~sigh~) Gary, let me apologize for not understanding your statements, but I'll stand by what I said to be wholly true. I've been corrected, and it's a true statement. Read below" Gary wrote: It does not matter what type of signal is modulating the signal when the linear amp is involved. Whether it is a sine wave or speech or anything else. The PEP rule still applies for 100% modulation! You can not exceed 100% positive peak modulation if the carrier is set at any level greater than 1/4 the PEP output capability of the amplifier. Unless you want to operate it in a non linear mode. Geoff Wrote: <>>I Disagree with that. Gary's statement is true. He is speaking of the PEP max output capability of the AMP. If the PEP maxoutput of the amp is 1000 watts then regardless of the symmetry of the audio, <>250 watts is the max carrier it should run on output. If asymmetrical then you would need to reduce the carrier to maybe 100 watts output. At 250 watts carrier output the amp would reach saturation before 100% modulation in any case. Sorry, sir. -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] GG 813 Linear in GE Ham News
In this case that is near correct. There is some feed through power also present. But the limiting factor is not always one half total plate dissipation. If the tubes were run in class A rather than B then output would be limited to much less than half the plate dissipation. At 33% efficiency in class A at full PEP the efficiency for the carrier would be 16.5%. Carrier power would then be limited to 41.25 watts plus a little feed through power. That's with an input of 250 watts. 73 Gary K4FMX Mike Dorworth,K4XM wrote: Actually, only one half of plate dissipation. The ICAS dissipation for a single 813 is 125 watts, CCS is 100 watts.. This is the maximum carrier for reasonable tube life. Efficiency is low without modulation., increases during modulation. Limiting factor is one half total dissipation.Sorry but the facts are so. Mike - Original Message - From: "W5OMR/Geoff" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, September 29, 2005 6:03 AM Subject: Re: [AMRadio] GG 813 Linear in GE Ham News Gary Schafer wrote: A pair of 813s in GG are only good for 150 watts carrier out on AM. 73 Gary K4FMX I'm not trying to start anything here, Gary, but that statement seems to be in stark contrast to what you said, yesterday... With an AM linear the efficiency at carrier must be / will be exactly one half what it is at PEP. Provided it is tuned properly. 73 Gary K4FMX What would the efficiency be of an AM Linear at carrier. (or maybe I'm not reading this correctly, because I've yet to have coffee this morning, and I -know- I probably should'n't be posting messages in this state... ;-)) -- 73 = Best Regards, -Geoff/W5OMR __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami
RE: [AMRadio] need help
The input impedance should be very near what the value of the resistor is. In this case 170 ohms. The 4-400's will most likely be run in AB1 so no grid current. I would put in a 50 ohm resistor instead. You should get enough drive with it. Figure what the bias voltage will be on the tubes. Then figure what the peak voltage will be from the exciter at 50 ohms. If the peak voltage will be greater than the bias voltage on the tubes then you have enough drive. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > Sent: Wednesday, October 19, 2005 10:46 AM > To: amradio@mailman.qth.net > Subject: RE: [AMRadio] need help > > I'd have used an MFJ 259B to actually measure the input Z. Alternatively, > you can always use a small tuner to "tune" the input. I do that anyway > with my Drake L4B, (use a small MFJ mobile tuner with meter). > > 4-400's, eh? Nice amp! If your plate voltage is high enough, you ought > to > get serious power out of that baby! > > 73, Ed, VA3ES > > > From: Edward B Richards <[EMAIL PROTECTED]>: > > I want to drive a linear amplifier with a rice box that requires a 50 ohm > load. > The linear amp uses an input to a 170 ohm, 80 watt swamping resistor to > ground, then > through a .001 mfd capacitor, then through a VHF parasitic suppressor > consisting of 4 turns of wire around a 47 ohm resistor, to the grids of > a pair of parallel connected 4-400A tubes. > > What I need to know is the impedance of the input. Is it close to 50 ohms > or do I need to use a matching network between the rice box and the > linear amplifier. > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami
RE: [AMRadio] Re: need help
I just looked up the 4-400 and I see it requires more bias than I had remembered for AB1 operation. It requires -130 volts with 2500 on the plate and 750 on the screen. So a 50 ohm resistor with 100 watts would only provide around 100 volts peak drive voltage. Not quit enough. A 100 ohm resistor should provide around 140 volts peak with 100 watts. That should work with little drive to spare. Probably the easiest would be a 200 ohm resistor (close to the 170 ohm resistor). A 4:1 balun should match it close to 50 ohms. A 200 ohm resistor and 100 watts should provide close to 200 volts peak drive voltage. I did this setup (balun and resistor) with a pair of grid driven 1625,s driven by my 20A. It worked well. Voltages were less of course! Stray capacitance will change things a bit. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of ne1s > Sent: Thursday, October 20, 2005 12:30 PM > To: Discussion of AM Radio > Subject: [AMRadio] Re: need help > > With a 50 ohm grid load on 4-400s, I think you'll find you'll get very > little amplification from the stage - the 40400 grid(s) want(s) to see > more > voltage. I went throught this exercise one (on paper), so went with a 1:16 > balun into a 800 ohm non-inductive resistor network in the actual design. > Problem was, I couldn't make it broadband enough to cover more than 3 > consecutive bands at a time, and finally resorted to a T network on the > input, loaded with about 2000 ohms worth of resistors. > > -Larry/NE1S > > Gary Schafer writes: > > > The input impedance should be very near what the value of the resistor > is. > > In this case 170 ohms. The 4-400's will most likely be run in AB1 so no > grid > > current. > > I would put in a 50 ohm resistor instead. You should get enough drive > with > > it. Figure what the bias voltage will be on the tubes. Then figure what > the > > peak voltage will be from the exciter at 50 ohms. If the peak voltage > will > > be greater than the bias voltage on the tubes then you have enough > drive. > > > > 73 > > Gary K4FMX > > > >> -Original Message- > >> From: [EMAIL PROTECTED] [mailto:amradio- > >> [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > >> Sent: Wednesday, October 19, 2005 10:46 AM > >> To: amradio@mailman.qth.net > >> Subject: RE: [AMRadio] need help > >> > >> I'd have used an MFJ 259B to actually measure the input Z. > Alternatively, > >> you can always use a small tuner to "tune" the input. I do that > anyway > >> with my Drake L4B, (use a small MFJ mobile tuner with meter). > >> > >> 4-400's, eh? Nice amp! If your plate voltage is high enough, you > ought > >> to > >> get serious power out of that baby! > >> > >> 73, Ed, VA3ES > >> > >> > >> From: Edward B Richards <[EMAIL PROTECTED]>: > >> > >> I want to drive a linear amplifier with a rice box that requires a 50 > ohm > >> load. > >> The linear amp uses an input to a 170 ohm, 80 watt swamping resistor to > >> ground, then > >> through a .001 mfd capacitor, then through a VHF parasitic suppressor > >> consisting of 4 turns of wire around a 47 ohm resistor, to the grids > of > >> a pair of parallel connected 4-400A tubes. > >> > >> What I need to know is the impedance of the input. Is it close to 50 > ohms > >> or do I need to use a matching network between the rice box and the > >> linear amplifier. > >> > >> > >> __ > >> AMRadio mailing list > >> Home: http://mailman.qth.net/mailman/listinfo/amradio > >> Help: http://mailman.qth.net/mmfaq.html > >> Post: mailto:AMRadio@mailman.qth.net > >> AMfone Website: http://www.amfone.net > >> AM List Admin: Brian Sherrod/w5ami > > > > > > __ > > AMRadio mailing list > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:AMRadio@mailman.qth.net > > AMfone Website: http://www.amfone.net > > AM List Admin: Brian Sherrod/w5ami > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami
RE: [AMRadio] Re: need help
Brian, It sounds like your 4-400's may have been in grounded grid? The -130 volts is easy to get with a little 120 to 120 volt transformer. No current involved with AB1 operation. You don't need a regulated supply. A pot across the supply to adjust the voltage works fine. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > Sent: Saturday, October 22, 2005 3:26 PM > To: Discussion of AM Radio > Subject: RE: [AMRadio] Re: need help > > It seems like my homebrew 4-400A pair used a 35 Volt zener in the > cathode return to bias off the resting current during key up or > silence between words on SSB. > > I can see why a 130 volt diode would need to dissipate > considerably more power as heat. > > Of course you could use a bipolar transistor with it's base held > at the appropriate voltage of 130V DC if it had a good > heatsink and could handle the 104 watts. > > On 22 Oct 2005 at 12:06, Jim Candela wrote: > > > Brian, > > > > This would eliminate 1 of 3 supplies needed. If > > the zener could hold the filament CT at 130 volts, > > then the plate would need to increase to 2630, and > > screen to 880 to restore the DC operating point as > > before. > > > > The zener would need to handle the combined 4-400 > > plate and screen currents, which could be upwards of > > 800ma for two 4-400's at max CW output. That zener > > would dissipate 104 watts! (.8 X 130). I don't think > > this is a very practical approach, but it is for > > biasing hi mu triodes in GG service where the zener > > wattage need is much lower. > > > > I have a Fisher stereo tube hi-fi amplifier that > > uses 7591's in P-P for about 30 watts / channel. This > > Fisher uses a weird combination of cathode bias on the > > output tubes to provide fixed bias. They use two of > > the 12AX7's with series connected filaments in the low > > level speech amp as a output tube cathode resistor. > > This provides 24 volts bias, and this is all bypassed > > for audio. Then they divide the 24 volts down with a > > divider to in effect provide a output tube quiescent > > current adjustment. This is neat because there is NO > > hum from the low level 12AX7's because their filaments > > are pure DC driven. > > > > There is ONE big problem with this approach. Since > > the 7591's are in AB1 mode, the cathode current > > increases with audio level. This increases the bias > > voltage as well making the 12AX7 filaments "pump" with > > audio peaks. The compromise here is to heavily bypass > > the filaments with a large capacitor, and to not crank > > the music too loud. > > > > I fought with this for a while, and not wanting to > > leave good enough alone, I added a active shunt > > regulator across the filament "cathode resistor" and > > made the turn on point just about 10% higher then what > > the cathode bias was running at. The result was pretty > > amazing since the overload point of this amplifier > > went up about 25% from before when using a sustained > > sine wave drive. > > > > The cathode bias situation with the 4-400 AB1 grid > > driven amplifier is workable, but I think the first > > glance simplicity of this idea is offset by a new set > > of issues similar to what I went through with my > > Fisher audio amplifier. > > > > Regards, > > Jim Candela > > WD5JKO > > > > --- [EMAIL PROTECTED] wrote: > > > > > What about using a 130 volt 5 Watt zener diode in > > > the cathode? > > > > > > On 21 Oct 2005 at 21:48, Gary Schafer wrote: > > > > > > > I just looked up the 4-400 and I see it requires > > > more bias than I had > > > > remembered for AB1 operation. It requires -130 > > > volts with 2500 on the plate > > > > and 750 on the screen. > > > > So a 50 ohm resistor with 100 watts would only > > > provide around 100 volts peak > > > > drive voltage. Not quit enough. > > > > > > > > A 100 ohm resistor should provide around 140 volts > > > peak with 100 watts. That > > > > should work with little drive to spare. > > > > Probably the easiest would be a 200 ohm resistor > > > (close to the 170 ohm > > > > resistor). A 4:1 balun should match it close to 50 > > > ohms. > > > > A 200 ohm resistor and 100 watts should provide > > > close to 200
RE: [AMRadio] High Voltage Power Supplies
Hi Eddy, The first thing I would do is get rid of those resistors and capacitors across the diodes! They can cause more problems than they cure. Especially if the resistors are carbon type. They change values tremendously. But if you want to still use old vintage diodes you should have resistors and capacitors across them. But use film resistors rather than carbon. I would put in all new diodes like 1n4007 or 1n5408, s. With modern diodes you should not put any resistors or capacitors across them. They can upset the reverse current balance in the diode string and actually cause failure. If you can use a bridge instead of a full wave circuit you will also have fewer problems with transients. With a bridge circuit there can be no reverse transients across the diodes as the large filter capacitors are always across the diodes. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Ed Swynar > Sent: Sunday, October 30, 2005 10:07 AM > To: Discussion of AM Radio > Subject: Re: [AMRadio] High Voltage Power Supplies > > Hi Jim, > > Many thanks for all the info! > > Well, mine is the "classic" late 70's era string of 7 diodes per leg, each > paralleled with a resistor / disk capacitor combo. The transformer is, > indeed, centre-tapped, & the design is full-wave rectification, the output > of which goes directly to a series of "parallel resistor-equalized" > high-voltage electrolytics. > > The transformer itself is a classic --- an old Fred Hammond job, with a > cast > iron(!) frame! The thing weighs-in at a "mere" 90 pounds! I got it surplus > NOS from an old surplus house in Montreal some 30 years ago now... > > I took a suggestion of Bry's, Jiim, & placed an RCA plug-in type surge / > transient suppressor that I happened to have available between the p.s. & > the AC outlet --- that is one thing that I'd never done before. If / when > the supply fails again in future, I'll most likely "upgrade" the silicone > string with some of the newer, more robust chunks of silicone that were > simply unavailable 30-odd years ago... > > ~73!~ Eddy VE3CUI - VE3XZ > > > > > - Original Message - > From: "Jim Candela" <[EMAIL PROTECTED]> > To: "Discussion of AM Radio" ; > <[EMAIL PROTECTED]> > Sent: Sunday, October 30, 2005 9:42 AM > Subject: Re: [AMRadio] High Voltage Power Supplies > > > > Eddy, > > > > It might be helpful if you describe that power > > supply topology. Is it full wave with transformer > > center tap, full wave bridge, and is the filter a pi > > type, choke input filter, etc. If this is an option > > for you, make a sketch, and scan it into a JPEG file, > > and upload it to the net soemwhere. I have net space > > if you email it to me. This way we can all look at > > your schematic, and comment better without guessing. > > > >In general diodes fail from two transient factors. > > The first is current surge, and the second is > > avalanche reverse voltage breakdown. Since you added a > > step/start circuit already, the current surge issue > > should be contained. That leaves reverse breakdown. As > > Brian mentioned, a transformer primary varistor (like > > V130LA10A, for 115 volts, or V250LA10A, for 220 volts) > > might help from power line transients. > > > > If you look at the Bill Orr handbooks around 1970, > > Bill goes into detail describing diode failure modes, > > and ways to protect them. This includes a custom > > series R-C across the transformer secondary, and > > across the filter choke (if choke input). Today's > > diodes are tougher, and this precaution is often > > unnecessary so long as good diodes are used, and the > > diode PIV rating is at least 2X what the formulas > > state you need. However diodes like the 1N4007 (1A 100 > > PIV) need protection, whereas diodes like the 1N5408 > > (3A 100 PIV) are a lot more rugged. In researching > > diodes, look for the term "controlled avalanche". > > These are the best because they can take repetitive > > PIV spikes beyond rating without turning into a piece > > of wire. The 1N4001 to 1N4007 series are not in this > > catagory. Unfortunately the data sheets sometimes omit > > the "controlled avalanche" term. > > > > Regards, > > Jim Candela > > WD5JKO > > > > --- Ed Swynar <[EMAIL PROTECTED]> wrote: > > > > > 'Morning All, > > > > > > I'm curious as to why I have to replace the silicon > > > diode strings in my 2500 VDC power supply about > > > every 8-10 years, or so...I just went through the > > > exercise again early this morning --- turned on the > > > B+ to my 2 x 813 linear, & got nothing back for my > > > trouble but smoke from inside the enclosed p.s. > > > unit... > > > > > > Opened it up, & the resistor across the relay in my > > > time delay circuit --- transformer primary side --- > > > was fried. I checked the conductivity of both legs > > > of my diode string (it's a full-wave set-up), & sure > > > enough, one leg was A-OK, but the other
RE: [AMRadio] Millen High Voltage Connectors
If you over tighten the millen connectors they will crack the shell of the chassis part pretty easily. You may not realize they have cracked. This can be a leakage point. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of david knepper Sent: Tuesday, January 10, 2006 8:05 AM To: [EMAIL PROTECTED]; amradio@mailman.qth.net Subject: [AMRadio] Millen High Voltage Connectors Thanks to all of you for your insightful suggestionis. In using coax connectors and coax cabling, I would recommend that one uses the red high voltage cable so as to clearly know the difference between an R.F. connection and a high voltage connection. I am going to try another set of Millen connectors since the input seems to be that the ones that I used were just defective. Most of the ARRL, etc. homebrew construction projects used those Millen H.V. connectors. Perhaps, expanding the mounting hole on the chassis slightly might place less strain on the insulation properties. Thank you again for taking the time to assist me. Dave, W3ST Publisher of the Collins Journal Secretary to the Collins Radio Association www.collinsra.com - the CRA Website Now with PayPal CRA Nets: 3805 Khz every Monday at 8 PM EST and 14255 every Saturday at 12 Noon EST __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
RE: [AMRadio] Negative Loading circuits - good, bad, or ?
Did you know that clipping an asymmetrical audio signal produces even order harmonics where clipping symmetrical signals produces only odd order products. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bob Bruhns Sent: Wednesday, January 11, 2006 9:43 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Negative Loading circuits - good, bad, or ? Thanks, Larry, I'll be interested in that. I understand that one large AM network - Clear Channel, I believe - is cutting their AM audio bandwidth to 5 KHz to make distant AM reception better (less splash from adjacent channels). I remember back in the late 60s, a little 250 watt daytime station on 540 KHz in Islip, Long Island ran some sort of clipping to sound louder. I don't know about splatter, but it really didn't sound good that way. It was pretty loud, though. But in amateur operation, some gentle curvature can curb the peaks that would get sharply snipped off by overmodulation, without a lot of splatter. Overall, it would probably reduce the general splatter level somewhat. Also it would be useful to have some kind of diode and resistor to catch peaks that do overmodulate, and keep them from making a voltage spike that could blow the modulation transformer. But if the circuit is being used to achieve high audio levels, then a low pass filter ought to follow the diodes. And the transient performance of the filter must be such that overshoot is minimized, because overshoot would overmodulate and splatter too. Generally a non-overshoot filter gives a soft cutoff rather than a sharp cutoff, unless it is complex and high order. I use low level asymmetrical clipping, and I can filter that with a 3.5 KHz low-pass filter in crowded conditions when I push the clipper hard. I accidentally found that a side chain servo loop could have its time constant aligned with the modulator, and produce very good clipping control, so that's how I do it. The clipper is really a limited amount of extremely fast peak limiting compression, with a time constant around a millisecond or so, riding on the slower 0.2 second time constant of the peak limiter, with a slower time constant coupled on a resistive divider for some slow average compression action as well. using a moderately complex RC network as a gain control loop filter. Because of this time constant, sibilents are treated with a more peak limiting action so there is less intermodulation, and lower frequency stuff is softly clipped. I shorten the time constant and increase the audio drive to push this harder, accepting some distortion for punch. When I push it like that, I use the low-pass filter, which is just a second-order Sallen-Key. I got a comment on how narrow the signal was, and yet it sounded clear because of upper midrange boost. The millisecond range time constant of the servo-clipper avoids a lot of high frequency harmonic generation before the audio hits the filter. Bacon, WA3WDR - Original Message - From: "Larry Will" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Wednesday, January 11, 2006 7:07 PM Subject: Re: [AMRadio] Negative Loading circuits - good, bad, or ? > Bacon, > > > I'll pull out a copy of the NRSC spec on the AM B'CST audio shelving > filter when I get a chance and pass along some details. > > > > Larry > > At 11:16 AM 1/11/2006, you wrote: > >Any distortion of the modulating waveform causes > >harmonic distortion and therefore splatter. The > >sharper a waveform discontinuity is, the more > >high-level harmonic energy it contains, and that > >harmonic energy becomes splatter on the air. This > >is why a low-pass filter is used in speech > >clipping systems. But the sharp clipping caused > >by overmodulation can not be filtered at the audio > >level. > > > >The extreme sharpness of clipping resulting from > >overmodulation is the reason that overmodulation > >causes so much splatter. The idea of the diode > >loading system is to produce a softer clipping > >that produces much less splatter than raw > >overmodulation. Additional diodes and resistors > >are often added to provide protective loading for > >the modulator on negative peaks that would have > >been unloaded in simple diode systems or with no > >diodes at all. This protective loading reduces > >voltage spikes that can destroy the modulation > >transformer. > > > >Some distortion is still produced with the diode > >loading system, and therefore some splatter will > >result. But unless there is some other problem, > >the splatter is much less severe than raw > >overmodulation, and the high frequency products > >caused by this action can be filtered at the audio > >level. You can add a high level splatter filter, > >although that will limit your high frequency > >response. You can have a few filters or a few > >filter settings, like 10 KHz for clear conditions, > >6 KHz for intermediate conditions, and 3.5 KHz for > >crowded con
RE: [AMRadio] Web page appears in opposition to RM-11306
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John E. Coleman (ARS WA5BXO) Sent: Tuesday, January 17, 2006 5:11 PM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] Web page appears in opposition to RM-11306 As for measure of power, it was 1KW DC input MAX as measured by the product of plate voltage and plate current meters with a time constants of .25 sec. As long as the product of the two meters did not exceed 1KW then you were legal. Typically, when these conditions were properly monitored, the max output obtainable by a legal SSB station was about 1500 watts PEP. I jokingly say, "the manufactures of SSB desktop equipment were sore about the AM stations that could get 750 to 800 watts of carrier and modulate it to 3000 watts PEP output (SINE WAVE) with out their plate current moving". Not joking, by the use of natural asymmetrical audio I was able to get about 7 KW PEP output with no plate current increase. Also there seemed to be a lot of dummying down of folks about that time. So, 1500 watts PEP output is about the same as ever for a SSB station but was a kick in the teeth for big iron home brewers of AM stations. John, WA5BXO 1500 watts PEP output is not the same as ever for SSB. The SSB guys lost right along with the AM guys on the maximum power level. At 1 kw average, or indicated on the plate meter, average output on SSB is around 600 watts. The PEP level of that much power will range anywhere from 3000 to 5000 watts. Just the same as it will with AM less of course the difference in amplifier efficiency. Watch the output power meter on your SSB rig when it is operated at 100 watts PEP output. The average output (on an average reading wattmeter) will indicate only around 15 to 20 watts unless you are using lots of compression or ALC. When not hitting any ALC the average will be quite low. However in years bygone most people thought that PEP was automatically twice what average power was. That is true with a two tone test signal but of course not with voice. Most amplifiers in those days were not built to deliver much more than 2 kw pep output so most did not realize what they had lost. A lot of folks thought they gained power with the new rules as now you could run around 3000 watts input indicated on the plate meter (in CW) for 1500 watts output. Many were confused about what PEP really was, including the manufacturers if you look at some of the old spec sheets on SSB gear. 73 Gary K4FMX
RE: [AMRadio] 32V-2 speech amp question
Hi John, I think this "hi-fi" thing gets carried a little far with a lot of people. I agree with you that most sound "not so good" with narrow receiver filters. Like you say unless it is a pretty much local qso you can't use wide bandwidth on the receiver. There is a lot of energy in the low frequencies. They do little for intelligibility. But if they are present they take away modulation power from the more usable frequencies in the audio bandwidth. The low frequencies will over modulate the transmitter before the mid range frequencies will so that limits the amount of energy that you can apply to the more useful mid-range. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of John E. Coleman (ARS WA5BXO) > Sent: Monday, January 23, 2006 11:19 AM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] 32V-2 speech amp question > > The 32V driver is certainly adequate for the specifications of the > rig. I might add that the specifications in fidelity are fine for me. I > think it and the 75A4 receiver could do better on THD. However, I think > Craig was looking for more fidelity. This might be a good time for me to > inject the Woos of HiFI. HIFI is OK for use on ground wave without > selective fading and of course when the spectrum is void of other QSOs. > The > problem that I have is the QRM/QRN that accompanies cross country QSOs > when > the band is open for that type of propagation. I narrow up the RCVR to > get > a better signal to noise ratio and that's when I begin understand the > problems of having bass without treble. I'm talking bass below 100 CPS. > It > sounds great when with a wide band pass and assuming the XMTR is passing > treble out to 15KHZ. But when you narrow down to 6-8 KHZ you need to roll > the lows of starting at 200HZ and eliminate them below 75HZ. I don't like > 60 CPS hum so I switch to a small very desk top speaker or cheap head > phones > to eliminate the bass. The XTMR would do better in this case not > transmitting the low bass but instead putting the energy into low > distortion > limited band width audio. > > This takes me to the new RMs that or in place. I can see all the sides as > having made good points. And I just don't know what to do. I feel that > the > FCC is going to get annoyed at the whole thing and wash there hands of it > and I don't know where that will leave us. > > John, WA5BXO > > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Brett gazdzinski > Sent: Sunday, January 22, 2006 7:04 PM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] 32V-2 speech amp question > > Keep in mind, the input impedance is very high, 1 meg at the mike > input stock radio. No transformer on the mike input in the 32v series. > I thought the driver transformer was adequate, its very large for a driver > transformer, the > DX100 has a postage stamp, the 32v had a fist sized driver transformer. > > I use a pair of KT88 tubes as modulators and don't use the driver > transformer > (gave it away a long time ago). If you run the high impedance mike preamp > in > the > rig and want some hifi, you have to run the mike preamp tube off DC. > I just did 1/2 wave (1 diode) and an electrolytic cap. The size of the cap > sets > the voltage the filament runs at. > The DC does not need to be pure, even rough DC will eliminate hum. > > Neg feedback, regulated voltage on the mod tube screens, large coupling > caps > will get you a long way to a good sounding 32V. > Brett > N2DTS > > > > > -Original Message- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of John > > Coleman ARS WA5BXO > > Sent: Sunday, January 22, 2006 11:03 AM > > To: 'Discussion of AM Radio' > > Subject: RE: [AMRadio] 32V-2 speech amp question > > > > I have not driven it externally before Craig but have some > > experience with the circuitry and the driver XFMR is a weak > > link in the > > circuit the XFMR barely has enough iron and coupling > > coefficiency in it > > to pass the low frequencies that the rig is designed for. As a matter > > of fact if the cathode resistor of the driver stage drops in > > resistance, > > as they or known to do with heat, the driver plate current > > will quickly > > saturate the driver XFMR causing the bass frequencies to look like a > > trapezoid instead of sine wave. If you were going to go with and > > outboard amplifier I would include a better driver XFMR as part of the > > external circuit and go to the grids directly. > > > > John > > Coleman > > > > -Original Message- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of Craig Roberts > > Sent: Saturday, January 21, 2006 10:19 PM > > To: Discussion of AM Radio > > Subject: [AMRadio] 32V-2 speech amp question > > > > Has anyone tried driving the mod input transformer of the > > 32V-2 (or V-3) > > > > directly with an outboa
RE: [AMRadio] AM Transmitter Advice??
He is telling you that a pair of 813's as a linear are good for only 125 watts of carrier output on AM and that it takes tubes with at least 800 watts plate dissipation to run the legal limit on AM linear. 73 Gary K4FMX 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of W1EOF > Sent: Monday, January 30, 2006 5:36 PM > To: Discussion of AM Radio > Subject: RE: [AMRadio] AM Transmitter Advice?? > > Dennis, > > I was with you until the end where you say: "Bottom line -- If you're > going > to build a linear do it right and go for a pair of 4-400's, single 4- > 1000A, > 3-1000Z or one of the big Russian tubes I've seen on eBay recently." > > Assuming one is going to build a linear, and so putting aside other issues > such as linear vs plate modulation, why do you think it makes a difference > what tube is used? Are you referring to running a linear at greater than > legal limit?. > > 73, > > Mark W1EOF > > > > > -Original Message- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > > Sent: Monday, January 30, 2006 5:01 PM > > To: [EMAIL PROTECTED] > > Cc: amradio@mailman.qth.net > > Subject: Re: [AMRadio] AM Transmitter Advice?? > > > > > > Linears for AM -- here we go again for at least the third time in > > the past 12 > > months. > > > > Basic considerations: > > > > 1. Under carrier only conditions a correctly designed and > > adjusted linear > > amplifier will be operating at about 33% efficiency. So, with a > > pair of 813's > > the math works out to 125 watts of carrier, obviously not worth > > the effort if > > you're starting off with a 100 W carrier exciter. > > > > 2. The linear must be initially tuned up at the peak RF output > > value which, > > in turn, requires that the exciter (or some other source) must be > > capable of > > providing the input necessary to do this. Typically, his would > > be 4 times > > the carrier value but expect to hear a lot more on this from the > > "asymmetrical > > speech waveform" crowd. > > > > 3. "Real AM" can only come from a plate modulated class C PA in > > the view of > > certain members of this community. At the same time, big mod iron is > > expensive and hard to find. Also, for a legal max rig the wall > > plug efficiency of > > "high level" and "linear" is not that much different in the final > > analysis. > > > > Bottom line -- If you're going to build a linear do it right and go for > a > > pair of 4-400's, single 4-1000A, 3-1000Z or one of the big > > Russian tubes I've > > seen on eBay recently. I use my HB 3-1000Z amp on both SSB and > > AM, BTW. Works > > FB. > > > > Good luck with the project. > > > > Dennis D. W7QHO > > Glendale, CA > -- > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.1.375 / Virus Database: 267.14.22/239 - Release Date: 1/24/06 > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
RE: [AMRadio] AM Transmitter Advice??
Actually the 10 watt ratting on the CE 10A/B is 10 watts PEP input. That gives around 5 to 6 watts output PEP for available drive. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Bob Bruhns > Sent: Friday, February 17, 2006 11:23 AM > To: Discussion of AM Radio > Subject: Re: [AMRadio] AM Transmitter Advice?? > > 12AX7s have surprised me with their power > capabilities before, but 20 watts output with 30 > watts input is 67% efficiency, and that means that > the 20 watts output is the PEP output of the > 3-12AX7 linear. I think that the 10W rating with > a 6AG7 is PEP as well. > > Bacon, W3WDR > > > - Original Message - > From: "Jim Candela" <[EMAIL PROTECTED]> > To: "Discussion of AM Radio" > > Sent: Friday, February 17, 2006 7:29 AM > Subject: RE: [AMRadio] AM Transmitter Advice?? > > > > > > > > Hi All, > > > >I recently had a conversation with a ham in > San > > Antonio (forgot his call), and he told me that > he > > built a unique linear amplifier for his central > > electronics 10a, and for tubes he chose 3 type > 12AX7 > > in parallel grounded grid. He said he could run > 30 > > watts input (300v @ 100ma) with no problems, and > about > > 20 watts out. I find it odd though that a 10a > can do > > 10 watts with a single 6AG7, and 20 watts is > only a > > 3db boost. > > > > To my way of thinking, a linear amp needs to > boost > > your power at least 6 db (~1 'S' unit) to be > worth the > > trouble. For us AM'ers, going from 100 watts to > 375 > > watts carrier does not meet the 6 db boost > criteria, > > and that explains why a good antenna on a DX-100 > is > > better than a average antenna on a Globe King > 500. > > > > Still, as I once posted last year, a dual 304TL > > grounded grid linear seems to fit the bill as a > 6 db > > 'brick' capable of 400 watts AM carrier output > with > > 100 watts AM input, or said another way it takes > 400 > > watts PEP and boosts it to 1600 watts PEP. There > was > > an old W6SAI construction project about this > (single > > 304tl GG amp), and I recall that the setup in > class C > > could run 1 kw dc input with over 1 kw rf output > > because of the low gain, and massive amount of > > feedthrough power from the exciter that finds > it's way > > to the output. This was a way around the FCC > power > > rules of the day. > > > > Regards, > > Jim > > WD5JKO > > > > --- Donald Chester <[EMAIL PROTECTED]> wrote: > > > > > >Assuming one is going to build a linear, and > so > > > putting aside other issues > > > >such as linear vs plate modulation, why do > you > > > think it makes a difference > > > >what tube is used? Are you referring to > running a > > > linear at greater than > > > >legal limit?. > > > > > > Well, go ahead and try building a legal limit > linear > > > that runs a pair of > > > 807's in the final. > > > > > > > > > __ > _ > > > > > > This message was typed using the DVORAK > keyboard > > > layout. Try it - you'll > > > like it. > > > http://www.mwbrooks.com/dvorak/ > > > http://gigliwood.com/abcd/ > > > > > > > > > > > > __ > > > > AMRadio mailing list > > > Home: > > > > http://mailman.qth.net/mailman/listinfo/amradio > > > Help: http://mailman.qth.net/mmfaq.html > > > Post: mailto:AMRadio@mailman.qth.net > > > AMfone Website: http://www.amfone.net > > > AM List Admin: Brian Sherrod/w5ami, Paul > > > Courson/wa3vjb > > > > > > > > __ > > > AMRadio mailing list > > Home: > http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:AMRadio@mailman.qth.net > > AMfone Website: http://www.amfone.net > > AM List Admin: Brian Sherrod/w5ami, Paul > Courson/wa3vjb > > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
RE: [AMRadio] FM transmitter
> If you want to hear your AM roundtable while you are called away to the > telephone or using the bathroom, get a good speaker, attach it to your > receiver, and turn up the volume. > An old cordless phone would do the trick. 73 Gary K4FMX
RE: [AMRadio] Modulator design needed
Just remember if you are going to use a tube phase inverter rather than a driver transformer the modulator tubes need to be run in AB1 and not AB2. You can't run any grid current without a driver transformer. This leaves out 807's as modulators as you can't get very much power out of them in AB1 but they are fine in AB2 as they are used in most rigs. Dx100 etc. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Peter Markavage > Sent: Sunday, March 26, 2006 1:34 PM > To: amradio@mailman.qth.net > Subject: Re: [AMRadio] Modulator design needed > > 12BY7 drives the driver transformer which, in turn drives the EL-34's. > > Build a phase inverter, like many of the Hi-Fi amps that don't use a > driver transformer to drive the EL-34's. > > Pete, wa2cwa > > On Sun, 26 Mar 2006 13:19:06 -0500 "Mike Sawyer" <[EMAIL PROTECTED]> > writes: > > Bob, > > I suggest you look at the schematics again. The output of the > > 5763 goes > > no where near the modulator. I don't have the schematics in front > > of me but > > I have done some extensive work in the audio section. > > Mod-U-Lator, > > Mike(y) > > W3SLK > > - Original Message - > > From: <[EMAIL PROTECTED]> > > To: <[EMAIL PROTECTED]>; "Discussion of AM Radio" > > ; > > "Discussion of AM Radio" > > Sent: Sunday, March 26, 2006 12:59 PM > > Subject: Re: [AMRadio] Modulator design needed > > > > > > Mark, > > > > Take a look at a Heathkit Apache schematic, (TX-1), for ideas. > > > > There is NO driver transformer. The 5763 driver goes to the Mod > > transformer > > and the EL-34s feed it for audio. > > > > Bob - N0DGN > > > > -- Original message -- > > From: "W1EOF" <[EMAIL PROTECTED]> > > > > > > I've been gifted a nice mod transformer so I can build a modulator > > for my > > > Johnson 6N2. I don't have a driver transformer so I'm looking for > > a design > > > which doesn't need one. I'm sure the schematics are out there, but > > I keep > > > finding ones with the driver transformer. Same with all my old > > radio books > > > that I've looked at so far. Can someone point me in the direction > > of a > > > good > > > design that is online, or one that you can share with me via > > email? > > > Thanks! > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
[AMRadio] RE: Modulator design needed
The 807's in the Viking and DX-100 run in AB2. In AB1 you wont get more than around 45 to 50 watts of audio before they start drawing grid current. In AB2 they will produce 120 watts of audio. 73 Gary K4FMX > -Original Message- > From: ne1s [mailto:[EMAIL PROTECTED] > Sent: Monday, March 27, 2006 1:06 PM > To: [EMAIL PROTECTED]; Discussion of AM Radio > Subject: Re: Modulator design needed > > While other tubes may do better, I've had good luck using AB1 807s in > VikingI/II/DX-100 class transmitters - they'll do 100% cleanly. > > -Larry/NE1S > > Gary Schafer writes: > > Just remember if you are going to use a tube phase inverter rather than > a > > driver transformer the modulator tubes need to be run in AB1 and not > AB2. > > You can't run any grid current without a driver transformer. > > This leaves out 807's as modulators as you can't get very much power out > of > > them in AB1 but they are fine in AB2 as they are used in most rigs. > Dx100 > > etc. > > > > 73 > > Gary K4FMX > > > > > >> -Original Message- > >> From: [EMAIL PROTECTED] [mailto:amradio- > >> [EMAIL PROTECTED] On Behalf Of Peter Markavage > >> Sent: Sunday, March 26, 2006 1:34 PM > >> To: amradio@mailman.qth.net > >> Subject: Re: [AMRadio] Modulator design needed > >> > >> 12BY7 drives the driver transformer which, in turn drives the EL-34's. > >> > >> Build a phase inverter, like many of the Hi-Fi amps that don't use a > >> driver transformer to drive the EL-34's. > >> > >> Pete, wa2cwa > >> > >> On Sun, 26 Mar 2006 13:19:06 -0500 "Mike Sawyer" <[EMAIL PROTECTED]> > >> writes: > >> > Bob, > >> > I suggest you look at the schematics again. The output of the > >> > 5763 goes > >> > no where near the modulator. I don't have the schematics in front > >> > of me but > >> > I have done some extensive work in the audio section. > >> > Mod-U-Lator, > >> > Mike(y) > >> > W3SLK > >> > - Original Message - > >> > From: <[EMAIL PROTECTED]> > >> > To: <[EMAIL PROTECTED]>; "Discussion of AM Radio" > >> > ; > >> > "Discussion of AM Radio" > >> > Sent: Sunday, March 26, 2006 12:59 PM > >> > Subject: Re: [AMRadio] Modulator design needed > >> > > >> > > >> > Mark, > >> > > >> > Take a look at a Heathkit Apache schematic, (TX-1), for ideas. > >> > > >> > There is NO driver transformer. The 5763 driver goes to the Mod > >> > transformer > >> > and the EL-34s feed it for audio. > >> > > >> > Bob - N0DGN > >> > > >> > -- Original message -- > >> > From: "W1EOF" <[EMAIL PROTECTED]> > >> > > > >> > > I've been gifted a nice mod transformer so I can build a modulator > >> > for my > >> > > Johnson 6N2. I don't have a driver transformer so I'm looking for > >> > a design > >> > > which doesn't need one. I'm sure the schematics are out there, but > >> > I keep > >> > > finding ones with the driver transformer. Same with all my old > >> > radio books > >> > > that I've looked at so far. Can someone point me in the direction > >> > of a > >> > > good > >> > > design that is online, or one that you can share with me via > >> > email? > >> > > Thanks! > >> __ > >> AMRadio mailing list > >> Home: http://mailman.qth.net/mailman/listinfo/amradio > >> Help: http://mailman.qth.net/mmfaq.html > >> Post: mailto:AMRadio@mailman.qth.net > >> AMfone Website: http://www.amfone.net > >> AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > > > > > > __ > > AMRadio mailing list > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:AMRadio@mailman.qth.net > > AMfone Website: http://www.amfone.net > > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb >
RE: [AMRadio] RE: Modulator design needed
> -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > Sent: Monday, March 27, 2006 10:23 PM > To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; amradio@mailman.qth.net > Subject: Re: [AMRadio] RE: Modulator design needed > > > In a message dated 3/27/06 4:48:02 PM, [EMAIL PROTECTED] writes: > > > > The 807's in the Viking and DX-100 run in AB2. > > > > I know the VII manual sez AB2 but no way with that triode connected 6AU6 > driver (AB1.25 maybe). A popular mod was to replace with a parallel > connected > 12AU7 which doesn't give enough kick either and the stock driver > transformer won't > handle AB2 power levels in any case. The stock VII audio system can > provide > just enough output for good sounding 100% modulation with a hot pair of > 807s and careful adjustment. Regulating the screens at 300 volts will > help a > lot too. Don't know what Heath did about the problem, but note that DX- > 100s > (pair of 1625s) usually sound quite good on the air. > > I modified my VII for proper AB2 operation with a 6AQ5 driver, 5W driver > xformer, negative feedback, and regulated screen and bias supplies. > Works FB but > a non-trivial undertaking. Swapped a pair of EL-34s for the 807s in > another > VII; regulated the screens but left the rest of the audio string original. > Worked just as well as the AB2 mod and MUCH easier to do. > > > Dennis D. W7QHO > Glendale, CA Part of the problem with the Viking II is that the modulation transformer has the wrong ratio. The modulator tubes are not loaded heavy enough and they go into clipping too soon. They designed it that way deliberately, I suppose to get a little high level clipping without the rig being able to severely over modulate. I think if you look at the grid voltage with a scope you will find that it does go into AB2 on modulation peaks. 73 Gary K4FMX
RE: [AMRadio] LV Supply
For 1 amp an LM317 voltage regulator should work just fine. Then you can just use a large capacitor on the supply in front of it and job done. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Rick Brashear > Sent: Wednesday, April 12, 2006 9:03 AM > To: Discussion of AM Radio > Subject: Re: [AMRadio] LV Supply > > Oops! I'm either going to have to start proof reading my posts better > or stop writing them so late at night. I meant to say "1 amp" maximum > load... Sorry for the goof. > > Rick > > > > Rick Brashear wrote: > > > Hi all... > > > > I am looking for suggestions on choke/capacitor combinations for a > > 13.8 vdc, 10 amp maximum load supply. I'd like to have the benefit of > > choke input regulation. I thought I had stuff here that would work, > > but have not found it yet, so I'll buy more and I want to be sure I am > > calculating things correctly before I let go of the hard earned cash. > > > > Thanks for any suggestions and help. > > > > Rick/K5IZ > > > > > > __ > > AMRadio mailing list > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:AMRadio@mailman.qth.net > > AMfone Website: http://www.amfone.net > > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > > > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
RE: [AMRadio] Modulator for DX60 available
EF Johnson mad a similar screen modulator to the one WRL made. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Rev. Don Sanders > Sent: Friday, April 14, 2006 11:56 AM > To: Discussion of AM Radio > Subject: Re: [AMRadio] Modulator for DX60 available > > Geoff, while you may not have seen it, > WRL made a screen modulator for a > couple of their CW only small transmitters > back in the 60's that was external to the > transmitter and plugged into an accessory > socket on the back of the transmitter. > Rather rare now. > BTW, I have copy of 2 articles for a > Bias-shift modulator from the 50's and > how to apply it to a DX60 for high > level plate modulation. It uses a > modulation choke for a form of > Heising modulation and used the > built in controlle modulator to drive > the modulator tube- usually the same > type as the final tube./ I recently > found a 6 henry 200 mil choke and > I am going to try it on my DX60B. > Healthfully yours, > DON W4BWS > - Original Message - > From: "W5OMR/Geoff" <[EMAIL PROTECTED]> > To: "Discussion of AM Radio" > Sent: Friday, April 14, 2006 9:27 AM > Subject: Re: [AMRadio] Modulator for DX60 available > > > > Alan Beck wrote: > > > > > I am sorry, did we work out how it could be interfaces with a DX 60? > > > Normally there is a transformer in parallel with the output plate I > > > think and modulation is applied to the other side to "squish" the RF > > > at Audio frequencies. > > > Is this what you mean by output iron? > > > > > > > > > John Lyles wrote: > > > > > >> I have a self contained, commercial looking modulator chassis that > > >> would work well with a DX60 sized rig. It uses a pair of 807s and has > > >> the input and output iron and driver tubes. It came from a SK's pile > > >> this summer. If there is interest, I would part with it to help out a > > >> DX60 conversion to high level plate modulation. Its a small thang. > > >> Technical details available upon request. > > > > > > > Alan, I'm pretty sure John's statement was meant to say that the > > external modulator he had, would work with a rig that was around the > > same size (ie: power output of around 50w) as a DX-60. > > > > Of course, we all know that typical high-level plate modulated AM > > requires a modulation transformer that is connected in series with the > > B+ supply from the power-supply of the final, to the final stage > > itself. The audio generated by a typical push-pull Class B modulator is > > coupled via the modulation transformer to the B+ line. > > > > I might be mistaken, but I don't think I've ever seen an 'external' > > modulator deck that was built with the intention of screen/grid > > modulating an RF final. > > > > Hope that helps clear up some confusion. > > > > -- > > 73 = Best Regards, > > -Geoff/W5OMR > > > > A: Yes. > > > > > Q: Are you sure? > > > > >> A: Because it reverses the logical flow of conversation. > > > > >>> Q: Why is top-posting annoying in email? > > > > > > > > __ > > AMRadio mailing list > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:AMRadio@mailman.qth.net > > AMfone Website: http://www.amfone.net > > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
RE: [AMRadio] antenna tuners
Hi Alan, No need to go away! You will get lots of good info here and asking / discussing is how to understand. As to resonant antennas, it makes no difference in how well they radiate. Resonance of the antenna is not required. SWR is not all that bad either as long as the transmitter sees a match, especially the solid state rigs. When open wire feed line is used there is usually very high SWR on the feed line. If you connect 450 ohm line to a half wave dipole which is normally in the 50 to 70 ohm range you have high swr on the feed line. And no, high swr on a feed line will not cause it to radiate. What causes feed line radiation is an unbalance between the two wires in the feed line. High SWR on coax line will cause a little more loss in the feed line due to the higher currents involved across the lower impedance of the coax. That is why when using open wire line that is 400 to 600 ohms, there is much less loss. The same power across a higher impedance means less current and less current going through the feed line wire means less power loss. An antenna tuner just matches the impedance seen at the transmitter end of the feed line to the 50 ohm transmitter output. If there is high swr on the feed line, any power reflected from the antenna is not wasted it is just re-reflected back to the antenna and eventually gets radiated. At HF even fairly high swr on coax lines does not cause excessive loss. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Alan Beck > Sent: Thursday, April 20, 2006 5:45 AM > To: AMRadio@mailman.qth.net > Subject: [AMRadio] antenna tuners > > I don't believe in them. > > If you can't resonate your antenna, then what are you doing? > > If you use a tuner, you are creating a voltage divider effect that > creates a reactive load in your shack, to ground that makes your antenna > "feed line + radiating elements". > > Over the years, the importance of having at least a 2:1 match with at > least 1.5:1 some where in the the antenna design. > > Proper antenna design for your favorite frequencies is the best choice. > > I currently use a multi-element dipole to cover 80,40,20,15 and 10 meters. > > I just use a VSWR bridge and back off the power when the SWR rises close > to 2:1. > > I am not saying my answer is the best, I am only stating my opinion. > > Just like microphones in the sound work I help out with at church. If > they are not singing into the mic, I cannot "fix it" without creating a > gain structure that is sucking up to feed back" > > You need to fix your problems at the source. > > I our cases, it is resonance of your antenna, by some means. > > Even my hamstick on my jeep does great due to attention to resonance. > > 73 > Alan > VY2WU > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
RE: [AMRadio] antenna tuners
> > Another factor causing loss with a high SWR is dielectric losses at the > recurring high rf voltage points along the line. At low impedances, it is > the resistive loss in the wire, and at high impedances, it is dielectric > losses that combine to cause signal loss. But SWR is much, much less > critical than most hams have been led to believe. It is my understanding that at HF only resistive loss comes into play. Dielectric loss isn't a problem until you get into vhf. 73 Gary K4FMX
RE: [AMRadio] antenna tuners
This is another tidbit to keep in mind for those that still may think that an antenna has to be resonant to give 1:1 swr. A dipole antenna rarely is 50 ohms at resonance. It is very dependent on height above ground as to what impedance it presents at the feed point. It can range anywhere from below 30 ohms to above 70 ohms. So if you cut your antenna so that you have 1:1 swr at the transmitter end of the coax, the antenna is probably not tuned to resonance! You have detuned the antenna to change its impedance that the coax sees. Only rarely does a resonant antenna turn out to be 50 ohms. 73 Gary K4FMX
RE: [AMRadio] antenna tuners
Hi Dave, What the MFJ will show you at the end of your feed line is the result of the feed line and antenna as you noted. The only way to know where the antenna itself is resonant is to measure it right at the antenna. Or you can measure it through a 1/2 wave length of feed line which will reflect what is at the antenna to the other end. However that is only good at one frequency, where the feed line is exactly 1/2 wave length. A coax length of anything other than a 1/2 wave length is going to transform the impedance seen at the antenna (if it is not 50 ohms) to something else at the other end of it. By having the meter in the shack showing a low swr or finding the frequency where the swr dips does not mean that is where the antenna is resonant. It only means that is the frequency where the impedance is transformed to best match the transmitter. It is not necessarily the resonant frequency of the antenna. If the antenna resistance at resonance is not 50 ohms, changing its length (or frequency) will introduce reactance which adds or subtracts from the resistance until it presents 50 ohms at a particular frequency. Note that it will present 50 ohms to the feed line but it will no longer be resonant. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of david knepper > Sent: Friday, April 21, 2006 5:22 AM > To: [EMAIL PROTECTED]; Discussion of AM Radio > Subject: Re: [AMRadio] antenna tuners > > Could you please explain, using an MFJ antenna analyzer, what is the meter > showing on the instrument? > > I would think that the total system, that is feedline and flat top or > antenna if you prefer, is resonating at the point shown on the meter? Or > am > I wrong? In any case, I love that device for checking out the "resonant" > point of the antenna system - note that I did not say just antenna. > > > Thank you > > Dave, W3ST > Publisher of the Collins Journal > Secretary to the Collins Radio Association > www.collinsra.com - the CRA Website > Now with PayPal > CRA Nets: 3805 Khz every Monday at 8 PM EST > and 14255 every Saturday at 12 Noon EST > - Original Message - > From: "Gary Schafer" <[EMAIL PROTECTED]> > To: "'Discussion of AM Radio'" > Sent: Thursday, April 20, 2006 10:12 PM > Subject: RE: [AMRadio] antenna tuners > > > > This is another tidbit to keep in mind for those that still may think > that > > an antenna has to be resonant to give 1:1 swr. > > > > A dipole antenna rarely is 50 ohms at resonance. It is very dependent on > > height above ground as to what impedance it presents at the feed point. > It > > can range anywhere from below 30 ohms to above 70 ohms. > > > > So if you cut your antenna so that you have 1:1 swr at the transmitter > end > > of the coax, the antenna is probably not tuned to resonance! You have > > detuned the antenna to change its impedance that the coax sees. > > > > Only rarely does a resonant antenna turn out to be 50 ohms. > > > > 73 > > Gary K4FMX > > > > > > __ > > AMRadio mailing list > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:AMRadio@mailman.qth.net > > AMfone Website: http://www.amfone.net > > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
RE: [AMRadio] antenna tuners
> -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of kenw2dtc > Sent: Friday, April 21, 2006 11:31 AM > To: [EMAIL PROTECTED]; Discussion of AM Radio > Subject: Re: [AMRadio] antenna tuners > > Gary K4FMX said: > > > By having the meter in the shack showing a low swr or finding the > > frequency > > where the swr dips does not mean that is where the antenna is resonant. > It > > only means that is the frequency where the impedance is transformed to > > best > > match the transmitter. It is not necessarily the resonant frequency of > the > > antenna. > > Would you agree that if the SWR was less than 1.5:1 at a given frequency > that one could say that the "ANTENNA SYSTEM" was resonant at that > frequency? Would you also agree that the antenna would take the same > amount > power, minus the feedline loss, as if the antenna were resonant? > > 73, > Ken W2DTC You could say anything you want. You could employ an antenna tuner to an antenna and line that by themselves have 20:1 swr at 50 ohms and tune the tuner until there is 1:1 coming out of it. You could then say that your "antenna system" was resonant. If the plate tuning network on your transmitter would match that same antenna and feed line directly without the antenna tuner, you could again say that your "antenna system" was resonant. It all depends on how much you want to include as your "antenna system". As long as you don't confuse yourself as to what is really happening at the antenna itself. My original comments were addressing the question of whether or not the antenna itself needed to be resonant for maximum performance. Which it does not have to be. Antenna resonance has nothing to do with the "amount of power that an antenna will take". The amount of power it will take has only to do with the construction of the antenna itself. Will it arc somewhere or melt the wire down etc. The amount of power that the feed line will take (over a flat line)is largely determined by the swr on the line. How hot it will get from the added current as a result of the swr or if it will arc from the added voltage due to high swr. 73 Gary K4FMX
RE: [AMRadio] antenna tuners
> -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Donald Chester > Sent: Friday, April 21, 2006 7:56 PM > To: amradio@mailman.qth.net > Subject: Re: [AMRadio] antenna tuners > > > > > I don't believe in them. > > > > > > If you can't resonate your antenna, then what are you doing? > > > I prefer to use just one dipole, centre-fed with open wire line, and use > multiband tuners to operate that same antenna on several bands. That way > it > is uniformly efficient all the way across each band, and I don't have the > clutter of multiple dipoles strung all around each other, or the > compromise > of an "all-band" antenna such as a trap dipole. > > With a proper tuner, the antenna, feedline and ATU all make up a resonant > system. Resonance can be changed by changing the length of the antenna, > the > length of the feedline, or the adjustment of the tuner, but it's the whole > system that is placed in resonance, not just the antenna wire itself, as > in > the case of a simple coax-fed dipole. > > Don k4kyv Hi Don, Let's say you changed the output impedance of your transmitter from 50 ohms to say 200 ohms. (changing nothing on the tuner) Would the "antenna system" (antenna, feed line and tuner) still be "resonant" as you had them tuned when you had the transmitter set for 50 ohms output? If you now retune the antenna tuner to accommodate the 200 ohm output of the transmitter, will the "antenna system" again be resonant? :>) :>) 73 Gary K4FMX
RE: [AMRadio] antenna tuners
> -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Donald Chester > Sent: Friday, April 21, 2006 7:15 PM > To: amradio@mailman.qth.net > Subject: RE: [AMRadio] antenna tuners > > >From: "Gary Schafer" <[EMAIL PROTECTED]> > > > > Another factor causing loss with a high SWR is dielectric losses at > the > > > recurring high rf voltage points along the line. At low impedances, > it > >is > > > the resistive loss in the wire, and at high impedances, it is > dielectric > > > losses that combine to cause signal loss. But SWR is much, much less > > > critical than most hams have been led to believe. > > > >It is my understanding that at HF only resistive loss comes into play. > >Dielectric loss isn't a problem until you get into vhf. > > I would say it depends on what kind of balanced line you use. If it is > well > insulated, real open wire line, with ceramic or low-loss plastic > spreaders, > there is probably negligible dielectric loss at hf or even lower vhf. But > if it is solid dielectric feedline, or even that pseudo-open wire line > stuff > that is basically heavy duty TV lead-in with square holes punched in the > dielectric, I suspect there would be dielectric losses even at hf, and > that > they would increase with substantial SWR. > > The same goes for solid dielectric or foam type coax. > > However, for moderate SWR's, the loss is much less serious than most hams > have been led to believe. > > Don k4kyv Actually the dielectric losses don't have much effect until high vhf and into UHF. Changing the dielectric material in coax from a solid to air dielectric where there is very little dielectric material, makes no significant difference in loss at HF. But the reason the loss goes down with air dielectric is because the center conductor is made larger and has less resistance loss. The center conductor has to be made larger to maintain the same impedance line. I think I read somewhere that the open wire line with the holes punched in the dielectric was no better as far as loss goes than if the holes were not there. But punching the holes allows for a little higher impedance line by lowering the capacitance so that lowers the loss. But the presence of less dielectric material itself had no effect on loss. Real open wire line will usually have less loss than the TV style line with the solid or punched dielectric between the wires because real open wire line will have a higher impedance than the other stuff. Usually the TV style line even if advertised as 600 ohm line is lower impedance. The punched hole stuff I think is advertised as 450 ohm line but turns out to be lower than that. 73 Gary K4FMX
RE: [AMRadio] antenna tuners
> > The point is, adjusting any one or combination of the following: the PA > tank > settings, the antenna tuner settings, the antenna turner coupling coil (if > link coupling is used), the length of the open wire feeder, the length of > the antenna, will affect the resonant frequency and thus the reactance vs > resistance of the network that couples the amplifying device at the final > amplifier to the aether. > > Don k4kyv > The question was meant to invoke some thought about what parts of the system come into play when we say things are "resonant". As we see from Don's explanation we can go right down to the final tank circuit when talking about making the antenna system resonant. The following will be true when the tuner is adjusted to provide a non reactive 50 ohm output to the transmitter: Assuming a 50 ohm link, if the link in the final is resonant (reactance is zero) then once the plate is dipped, moving the link to change coupling should not change plate resonance. If the link is not resonant then it will affect the plate circuit resonance when its coupling is changed. If the antenna tuner does not match the link on the transmitter the link will have a reactive component that will effect transmitter plate tuning. Now the transmitter plate tuning will be part of the whole "antenna system resonance". This is why I don't like to refer to the "antenna system" being resonant. Too many things can be involved and we loose sight of what we really mean. The same is true if you feed a coax fed dipole directly from the pi network output of your transmitter. Or use a tuner that is not tuned for a flat match to the transmitter. The plate and load tuning becomes part of the "antenna system tuning" if you are to use that terminology. If we think of feed lines as transformers (whether they are open wire or coax) and antenna tuners as variable transformers it makes things easier to see. When using an antenna tuner and we tune the reactance out of the circuit so we only see a resistive component we can say it is resonant. But what is really resonant? The antenna is not, the feed line is not, the tuner is not. The only thing resonance means in this case is that the capacitive and inductive reactances at the tuner are equal. It confuses many people. 73 Gary K4FMX
RE: [AMRadio] antenna tuners transmission lines and more
Hi John, Boy you can tell you are an AM'r with the long post! :>) In some of the following I am saying the same thing as John with a little different explanation. Some is a bit of a correction. Lots of good stuff from John! I don't consider myself an expert either. This was going to be rather short but... SWR: The swr on a line can be found by measuring voltage peaks or current peaks on the line as you described. To truly measure swr the line must be at least a quarter wavelength long. What we normally measure with our swr meters or watt meters is an impedance ratio, which can be done on any length of line. The impedance ratios are representative of the standing wave ratios but we are not directly measuring standing waves. The impedances are compared to a resistor in the Swr Bridge. LINE LOSS: High swr "can" be an indication of wasted power but in the form of feed line loss if the feed line is a low impedance line such as coax. High swr can produce very currents on the line which result in I squared R loss. High swr on a higher impedance line is not usually much of a problem because the I squared R loss is much lower due to the current being less just because the line is higher impedance. TUNERS WASTING POWER: A tuner can dissipate substantial amounts of power depending on the load it is trying to match and if it is not adjusted properly. Even one with high quality components. For example the most common T type tuner can be misadjusted with the improper L /C ratios causing very circulating tank currents which heat the coil substantially. But if adjusted properly this is not usually a problem. REFLECTED POWER TO THE FINALS: As you noted high swr is an indication of reflected power on the feed line but that reflected power does not make it back to the finals in the transmitter. The reason it does not is because any reflected power that comes back down the line is re-reflected back to the antenna and eventually gets radiated. It gets re-reflected by what is called a conjugate match at the antenna tuner or the final tuning. A conjugate match presents an equal and opposite match to the line at the antenna tuner end of the line as what the mismatch to the line is at the antenna. If the line presents an inductive reactance at the tuner then the tuner must present an equal amount of capacitive reactance to the line. That is what some people call "resonance". That gives a flat, no swr, between the radio and the tuner. All the reflected power that came back to the tuner will be reflected back to the antenna at that point. RADIATION RESISTANCE: The definition of radiation resistance is, The total EM power radiated in all directions divided by the square of net current causing the radiation. In other words radiation resistance is equal to, a resistor if substituted for the antenna, that would absorb the same amount of power that the antenna radiates. Radiation resistance is not the feed point resistance of an antenna. The feed point resistance of an antenna also includes resistive losses in the wire. Power dissipated in that resistance is wasted in heat. FOLDED DIPOLE: The radiation resistance of a folded dipole is the same as that of a regular dipole. Even though the "feed point resistance" is 4 times as high for a folded dipole its radiation resistance is the same as a regular dipole. The folded element in the folded dipole only acts as an impedance transformer just like a 4:1 balun would do. The same holds true for a vertical monopole with a folded element to raise the feed point resistance. The radiation resistance is still the same as if the monopole were fed in the normal manor at the bottom against ground. SHORT ANTENNAS: A short antenna will radiate just as well as a full length antenna. As a matter of fact an infinitely small antenna will radiate just as well as a 1/4 wave or 1/2 wave length antenna. The problem is getting the power into the short antenna. A loaded mobile antennas radiation resistance is usually very low, in the order of a few ohms. Adding a loading coil to raise the feed point resistance to 50 ohms still leaves the radiation resistance of the antenna itself at those low few ohms to work against ground in getting power into the antenna for it to radiate. The coil dissipates most of the power applied in heat. If only 1 watt actually is radiated by a short mobile antenna it will produce the same signal strength as a full quarter wave length antenna with the same amount of power radiated. RADIATION RESISTANCE OF A FULL WAVE DIPOLE: I believe the radiation resistance of a 1/2 wave dipole is in the neighborhood of 2000 to 4000 ohms. I think it is the same as what the impedance at the end of a 1/2 wave antenna would be. I saw once how to calculate it. I will have to dig around again. Again I believe that an infinitely long dipole will have a similar radiation resistance to the full wave dipole. RHOMBIC ANTENNA: A rhombic is a different antenna than just a long dipole.
RE: [AMRadio] antenna tuners transmission lines and more
> -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Brian Carling > > The power may not be wasted very much in the tuner, BUT > REFLECTED power goes back into the RF final and is disippated > in the famil amplifier device(s) - at least many people have > written articles for decades describing that marticular "myth" > or so-called "FALSE STATEMENT." I am not so sure it is false > though! Look at your bird wattmeter, or any other directional wattmeter, in a line that shows reflected power. Note that the forward power reading will be higher than the actual power delivered by the transmitter. Example: If your transmitter puts out 100 watts and it feeds a load that presents 20 watts reflected, your wattmeter will read 120 watts forward and 20 watts reflected. If you look in the bird manual it will tell you to find the amount of power delivered to the load you subtract the reverse power reading from the forward reading. In this case you would subtract the 20 watts reflected from the 120 watt forward reading. That gives you 100 watts delivered to the load. The same amount of power that the transmitter is putting out. There is no reflected power left to get back to the finals! Prove it to yourself: Put a wattmeter at your transmitter. Run some coax to an antenna tuner, then another wattmeter, then a 50 ohm dummy load. Adjust the tuner so the first wattmeter shows 20 watts reflected and 120 watts forward. The wattmeter at the load will read 100 watts. The tuner is simulating a mismatched load while you are able to measure actual power into the load. Or you can use a non 50 ohm load and measure the voltage across that load to find actual power into the load. See my explanation in my other post about reflected power as to how it happens. 73 Gary K4FMX
RE: [AMRadio] DRM from Las Vegas this week
Some of this seems a little backwards. The typical CB 1/4 wave antenna is a rather low angle radiator not a high angle radiator. The major lobe is very low, less than 10 degrees. Many higher angle lobes do occur however. Antenna height as a great effect on take off angle, typically lower angle at greater heights. Ground conductivity has a great effect on sky wave signals as part of the signal is reflected from the ground and adds to the direct part of the signal. Even antennas mounted high off the ground. It is not only the ground conductivity in the close in area but also in the far field that matters, especially with a vertically polarized antenna. The "local" coverage is line of sight so it has little influence by ground conductivity as you say. Ground wave propagation (more correct, surface wave) is highly attenuated much above 3 Mhz so at 11 meters there is almost no ground wave at all. "Suppressing the sky wave signal on 11 meters"? Sounds like a job for a fractal antenna. :>) The better you make the "local" wave the better you are going to make the sky wave signal as Steve notes. I would have to agree with Steve, sounds like a good DX antenna! 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Larry Will > Sent: Friday, April 28, 2006 6:59 PM > To: Discussion of AM Radio > Subject: Re: [AMRadio] DRM from Las Vegas this week > > Steve, > > Your points are correct and well taken but not the whole story. No > doubt that F2 skip can be very low angle and rhombics used at HF are > designed for that. (Takeoff angles of say 2 to 10 degrees with good > suppression above that) And local bcsting on 26 MHz would have > trouble with F2 skip. But E skip (the usual CB kind) and nighttime > AM are another matter. My station had the tall towers to protect > co-channel stations at 350 to 600 miles AT NIGHT not to cancel > skywave close in (35-60 miles) at critical hours. This is not unusual. > >The typical 1/4 wave CB antenna has a very high angle of radiation > and thus dumps most of the power at 25 to about 70 degrees thus fully > illuminating the E layers day and night. It doesn't mater whether > the antenna is on the ground or on a tower, the skywave radiation has > nothing to do with ground conductivity (nor does the local coverage > from a 26 MHz transmitter. The "direct" wave is what you pick up > locally on 26 MHz, the poor GC causes the "ground" wave to not travel > very far even with very high power. > > TCI has a very solid reputation on designing HF antennas and I am > sure that they can propose or have even installed anti-skywave > antennas for the 12 meter shortwave band (where the DRM tests were done). > > > Larry > > > At 02:15 PM 4/28/2006, you wrote: > > >Larry wrote: > > > > >Think AM. At WCZN we used a .42 wavelength vertical which has great > > >null suppression at medium elevation angles. (20-40 degrees as I > > >remember without looking it up.) See any text on vertical radiators. > > > >I understand that well, but it isn't the same situation. One medium wave > you > >want to eliminate the higher angles of radiation to avoid creating > >interference to your own ground wave coverage out toward the fringe. > >But your low angle > >of radiation is putting a lot of energy straight out toward the > >horizon, which > >would be good for DX (the skip distance is much farther out). Losses > from > >the MF wave being in contact with the ground reduces that somewhat, but > not > >much. On the Virginia coast I had a 5/8-wave tower on 1310 kHz that > >got reception > >reports from Africa. > > > >In the situation on 26 MHz the same rules apply, only the ground losses > are > >lower as the antenna is well above the ground (space wave rather than > ground > >wave). In any case, if you put a lot of energy out toward the horizon > you'll > >have great DX. > > > >I could design an antenna that would put the minimize the DX by aiming > the > >main lobes down from a tall tower or mountain into a valley - as is done > with > >beam-tilt on FM andf TV antennas. But the DRM rep indicated they > >were using a > >simple dipole on the tower - I'm pretty sure that will talk around the > world > >when 11m opens up. > > > >Even the minor lobes on a beam-tilted antenna would propagate long > distances > >on 11m. For "local" broadcasting 26 MHz seems a poor choice. Remember > that > >4-watt CB was meant to be local, but when ever the band opens you'd hear > a > >might roar of thousands of those rigs "skipping" in. > > > >Steve WD8DAS > >__ > >AMRadio mailing list > >Home: http://mailman.qth.net/mailman/listinfo/amradio > >Help: http://mailman.qth.net/mmfaq.html > >Post: mailto:AMRadio@mailman.qth.net > >AMfone Website: http://www.amfone.net > >AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > >
RE: [AMRadio] Re - response to input to screen grid amplifier
This sounds like a class C linear screen driven amp. I couldn't find the article on it but W9VMQ built such an amp using 6DQ5's in the early 60's. I think he also did some experimenting with the 813 also. I think the article was in Ham Radio magazine. Maybe someone can do a search for it. Probably around 1963 to 1965? 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of John E. Coleman (ARS WA5BXO) > Sent: Tuesday, May 23, 2006 7:34 PM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] Re - response to input to screen grid amplifier > > Bill does the screen have a DC path to ground through the tuning coil? I > see no way that you can have grid current with no RF on the Grid. Perhaps > there is a hidden wire connecting the grid and the screen together. > > I am sending you a PDF on the 813 just to make sure that you have a > correct > one. > > > John, WA5BXO > > > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
RE: [AMRadio] How the reply button works
Every other list that I subscribe to operates the way you now have it set. That is how I would prefer it to be. Reply: goes only to the sender. Reply to all: goes to the list. When you set it the other way the only way to reply to an individual is to cut and past his address. Everyone should be encouraged to reply to the list with any info that may be of interest to most. 73 Gary K4FMX > Everyone, please send your vote to list so we can all feel confident > in the final decision. I say we close the poll by next Sunday, 18
RE: [AMRadio] Tower Construction
Be careful when giving this advice. A UFER ground is a good SUPLEMENTAL ground in a tower base but it should not be the only ground. A large area like a floor of a building provides more surface for the lightning to dissipate. A tower concrete foundation may not be large enough by itself and there is the possibility of poor connections inside so that the concrete crack from a lightning strike if it is the only ground connection. It is always recommended that ground rods be attached to each tower leg in addition. 73 Gary K4FMX > > DO RUN THE GROUND THROUGH THE CONCRETE! Take a look at the information on > this site first though. You may be glad you did. > > http://www.scott-inc.com/html/ufer.htm > > Best Regards, > Steve White, W5SAW > SW Commercial Electronics > > > -Original Message- > From: Ed Swynar [mailto:[EMAIL PROTECTED] > Sent: Saturday, June 10, 2006 2:16 PM > To: Discussion of AM Radio; [EMAIL PROTECTED] > Subject: Re: [AMRadio] Tower Construction > > > Hi Dave, > > I have a 48' tall, tapered, self-supporting "Delhi"-brand tower --- 6 > sections at 8' long each. > > The prescribed / manufacturer's recommendation is to bolt a 3' straight > formed extention at the base of each leg (total of 3), & to "suspend" > these > (a temporary wooden "cradle" will do admirably, as the cement sets) in a > hole dug 4' square, & 4-1/2' deep --- the cement is to come but a few > inches > below the bottom legs of the actual tower section. > > Oh yes --- the bottom 1' of the square hole is to be "belled" outward a > foot, or so. > > The documentation says this is good for heights of up to 64', or so...I've > never gone beyond 48', & have never, EVER had an ounce of trouble in the > two > locations that I've had my tower up. > > BTW, the top of the tower as an old Cornell-Dubelier AR-44 rotator, & a > 3-element Hy-Gain TH3 MkIII triband yagi... > > Use "industrial"-grade coarse cement, & do NOT run any ground leads > through > the block itself! > > ~73~ Eddy VE3CUI - VE3XZ
RE: [AMRadio] Tower Construction
>This affords you the > opportunity > to bond the tower, rebar, AND several copper clad ground rods together for > the best possible DC ground for your tower. If you want an RF ground > return > for your installation, install a heavy duty copper ring and bond it to the > ground rods. > Best Regards, > Steve White, W5SAW > SW Commercial Electronics A good lightning ground is also a good RF ground. This means several radials should be installed along with the ground rods. A ring connecting ground rods around the tower does nothing for a lightning ground. The lowest impedance is in a straight line out away from the tower. A sharp turn at the junction of the "ring" to get over to the next ground rod in the "ring" looks like a high impedance path to the lightning as the sharp turn has considerable inductance. Also the other ground rods in the ring are already at the same potential as they are connected directly to the tower. The lightning will be carried out away from the tower in all directions. There will be no current carried by the ring connection so it is a waste of wire. The ground system would be better served by using that wire for another radial. 73 Gary K4FMX
RE: [AMRadio] Re: upside down reply buttons, sending to whom, and tops VS bottoms and other non AM tech stuff
> -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of W5OMR/Geoff > Sent: Monday, June 12, 2006 10:52 PM > To: Discussion of AM Radio > Subject: [AMRadio] Re: upside down reply buttons, sending to whom, and > tops VS bottoms and other non AM tech stuff > > John E. Coleman (ARS WA5BXO) wrote: > > >This is almost like discussing politics on the air. HIHI > >But I will make a comment here any way. > > > >Dino and Geoff > > > > [much deleted] > > > >Brian > > > > [... again...] > > > John, your comments didn't go unread by me... but the way the list is > set up now, I'm fairly certain that only *I* got your reply. > > This is what the major crux of the problem is. Most people, when on a > list, just hit 'reply', and go. When the list is setup the way it USED > to be, the reply would go to the list. That's the way a Discussion list > is SUPPOSED to be.. so folks can DISCUSS (in my not so humble opinion). > > When you only reply to the sender, who has put something on the list, > then everyone else on the list suffers if someone only replies to the > sender, because the rest of the list can not benifit from the wisdom and > knowledge of someone's reply to a question. > > It is for that reason, above most all others, that I say leave the reply > option in the list software, as a reply-to-list function. If you -need- > to reply to an individual, then click 'reply to all' and that will THEN > include the original sender (as well as the list), and then it's a > simple matter of removing the discussion list address, so that the reply > only goes to the individual, instead of the whole list. Geoff, The problem is, it does not work that way! The way it was set up before, hitting "reply" or "reply to all" did exactly the same thing! They would both reply ONLY to the list. Neither would list the sender if you wanted to reply only to him. The way it is now you have a choice. 73 Gary K4FMX
