Re: [AMRadio] 78 records
Anyone know what the old thick records are worth these days? 73 Gary K4FMX -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio- boun...@mailman.qth.net] On Behalf Of jon baker Sent: Thursday, January 21, 2010 7:19 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] 78 records Larry, The 80 RPM records were made for the Edison players, which used a real diamond stylus. They are ruined by playing on a Victor or other player with a steel needle. One of my Edison records was recorded by Thomas himself, a plea for War Bonds during WW1. Please save the thick ones for a real Edison machine. Jon AD5HR --- On Wed, 1/20/10, Larry WA9VRH wa9...@dishmail.net wrote: From: Larry WA9VRH wa9...@dishmail.net Subject: Re: [AMRadio] 78 records To: Discussion of AM Radio in the Amateur Service amradio@mailman.qth.net Date: Wednesday, January 20, 2010, 8:17 PM Hi Bob, Go ckeck out the local antique malls. We visit one in Princeton Il about 50 miles North of Peoria that have tons of 78's. I am always looking for the 80 rpm's that are at least twice as thick for the windup phonographs. 73 Larry WA9VRH If you can't find any there is an antique place here in Peoria that may have some. I can stop by there on my way home one day. Larry - Original Message - From: Bob Peters rwpet...@swbell.net To: 'AM' amradio@mailman.qth.net Sent: Wednesday, January 20, 2010 3:10 PM Subject: [AMRadio] 78 records Hi guys, Maybe a little off topic but I need a couple 78 records preferably big band type. I just got a nice am/sw radio and record player with a 15 inch speaker that is 4 feet tall and about 20 inches wide. Had the turntable fixed and cartridge fixed so all is working and no records. Thanks, Very Best 73's, Bob W1PE Mesquite,TX http://www.w1pe.com http://www.myhamshack.com/W1PE/ Blog __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail- archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail- archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail- archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Speaker question
If you guys want some real base response I have a pair of 30 inch sub woofers each mounted in 36 cubic foot enclosures with 1 1/2 inch thick walls. These will supply true 16 Hz response with very low distortion. And they will shake your pant legs if you desire. They are for sale if someone is interested. For a general purpose speaker a car radio oval speaker is hard to beat. 73 Gary K4FMX -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio- boun...@mailman.qth.net] On Behalf Of CL in NC Sent: Tuesday, October 20, 2009 5:13 PM To: amradio@mailman.qth.net Subject: [AMRadio] Speaker question I looked over the speakers at Parts Express just to see what they have. The freq resp. of that $20 woofer is up to 2200 cycles. There was a 'Pro' speaker that went to 6600 cycles. Can a 10 diameter speaker, achieve a wide response when it has to move that large of a cone? The single 8 and 10 inch speakers in the old cabinet TV's and radios, I wonder what they would have tested out to freq. resp. wise. Always thought those old radios and TV's sounded good because it was bassy due to the large speaker. When you cranked up the treble, if it even had that option, it would get tinny sounding and lower audio out. They never did any fancy encloser either, just a hole in the cabinet somewhere and some wood screws. I still use an 8 speaker from a 1950's era Silvertone BW console TV, and still sounds great. Forget foam suspended speakers, the air pollution always attacks the foam and they give up the ghost. But, that seems to be all you can find in the larger speakers now-a-days. Charlie, W4MEC in NC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Speaker question
Hi Jim, I used to have these things hooked up to my hi-fi system. They were built to be used with original Quad electrostatic speakers with a Mark Levinson reference system, if you know what that was. One of the most accurate, clean sounding systems of the day. They still do an excellent job but now I have powered subs that don't take up so much room. These things are setting back in the corners of a room. 73 Gary K4FMX -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio- boun...@mailman.qth.net] On Behalf Of Jim Wilhite Sent: Tuesday, October 20, 2009 6:54 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Speaker question Roll those things to the door and feed them with a audio amp at 20 cycles and listen to the dogs howl. What size is your studio anyway? :) Jim/W5JO - Original Message - From: Gary Schafer garyscha...@comcast.net If you guys want some real base response I have a pair of 30 inch sub woofers each mounted in 36 cubic foot enclosures with 1 1/2 inch thick walls. These will supply true 16 Hz response with very low distortion. And they will shake your pant legs if you desire. They are for sale if someone is interested. For a general purpose speaker a car radio oval speaker is hard to beat. 73 Gary K4FMX __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Henry Plate Current Meter needed
There are some henry parts on QTH.com for sale. Not cheap but he does have the meters. Ad #733267 - 73 Gary K4FMX -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio- boun...@mailman.qth.net] On Behalf Of ronnie.hull Sent: Tuesday, April 07, 2009 5:24 PM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] Henry Plate Current Meter needed well I bought myself a henry 2k desktop that lasted one week :( I need a plate current meter. This is the OLD style henry with the tear drop shaped meters. Please help me salvage this amp and not have to throw it in the dumpster LOL Thanks Ronnie W5SUM __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] FW: Heath Apache symptoms
I accidentally erased the original message so replying here. With drifting plate current and low grid drive the first thing I would check is the adjustment of the clamp tube circuit. Low grid drive will cause the clamp tube to reduce screen voltage. Or maybe the clamp circuit is adjusted right and you just don't have enough grid drive. All bands?? 73 Gary K4FMX -Original Message- From: amradio-boun...@mailman.qth.net [mailto:amradio- boun...@mailman.qth.net] On Behalf Of George Brand Sent: Wednesday, January 07, 2009 11:23 AM To: amradio@mailman.qth.net Subject: [AMRadio] FW: Heath Apache symptoms Amen John! When I first bought a DX-100 at a swap, I took it to work and carried it up two flights to the workshop. (worked for a radio station) Got it up there and thought dang, I must be getting old 'er something Sat down, put feet up to read to my horror the !...@#$%^*() weighed 100 lbs soaking wet. I had the freight elevator take it down... As the owner of two Apaches, I'd like to see the answers posted to the list George wa8sco - I am not as strong as I was when I became a Novice over 50 years ago. Before you laugh, let me say that if you are LUCKY, maybe you will live to get WEAK!! Hi!! HI!! Thanks in advance and 73, John, K5PGW __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body.
[AMRadio] 5514 tubes
I acquired an rf section with a pair of 5514 tubes in it awhile back. Does anyone know what a 5514 is? They look a little like an 811 or 812 Thanks Gary K4FMX __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Re: New AM Swap list
No one was erroneously put on the swap list. All that was done was to split up the Am radio list into AM radio and AM swap list. All the subscribers were also set up on the AM swap list by the kindness of the list administrator. It is no different than when the list was moved to another server and all the members were moved by the administrator. But since some people apparently bitched about being signed up on a list without them doing it themselves (probably before they read what was going on) the administrator removed all from the new list and advised everyone to sign up themselves. So much for him trying to be helpful. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Saturday, March 08, 2008 10:36 PM To: amradio@mailman.qth.net Subject: [AMRadio] Re: New AM Swap list What did I do wrong? First, I received a welcome message telling me how to unsubscribe. Then a received a Dear John with no information other than you're out! I and many others received the same stuff in their inboxes recentlyleaving me to wonder when I had subscribed to another email list..then it occured to me, someone without asking first, dumped my email address among others into a new list. You knowit would have been great to have been told about such a new list -BEFORE- someone subscribed me to it. My email address is not a free for all for anyone to use as they see fit. Domain names get black listed when acts like the above mentioned occurs. Next time whomever creates a list...create it, test it with your own email addresses then put the word out. Auto subscribing some email addresses that are not yours to list without prior consent is just plain wrong. Bob Carter - KC4QLP __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Drake L-4B on AM
-Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of A.R.S. - WA5AM Sent: Thursday, March 06, 2008 10:43 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Drake L-4B on AM On Thu, Mar 6, 2008 at 9:37 AM, kenw2dtc [EMAIL PROTECTED] wrote: BTW, I tuned the amp for exactly 1500 watts output, then reduced the drive to exactly 25 watts without re-tuning the amplifier Actually the best way is to tune for 1500 watts out and reduce the drive until the output is 375 watts under carrier conditions. Also if you have one of those male voices that that will peak more in one direction than the other (if the audio is phased correctly) you must also de-rate the output power even more. Naturally, a scope and an audio generator is the preferred way to tune up a linear under AM conditions. 73, Ken W2DTC You're right Ken. I think I used 25 watts as a good figure, however 544 watts of carrier should modulate to over 2100 watts with a pure sine wave. I may try it again later and reduce the drive level to the point where the carrier output reaches 375 to see the difference. I suspect if anything the eff. will drop even more... Thanks. Brian / wa5am With an amp properly tuned for AM operation the carrier efficiency should be (theoretically) exactly 1/2 of what it is at PEP or full carrier out. Also drive power should be right around 25% of what it takes for full carrier. An amp that puts out 1500 watts with 100 watts of drive should put out around 375 watts with 25 watts of drive, assuming the amp is linear. Not all amplifiers are perfectly linear so this can vary one way or the other a little. This particular amp would have a gain of 15. The gain of 15 figure should hold close no matter how much drive is applied. The output should always be 15 times the drive power if the amp remains linear. The efficiency will vary with drive power. All these parameters are assuming that once the amp is tuned up for maximum output that the tuning is not touched as drive power is varied. If the efficiency of this same amp is 60% at full power out (1500 watts) then the efficiency at 375 watts out should be right close to 30%. As modulation is applied the efficiency of the peak envelope power will be 60%. 73 Gary K4FMX __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] New AM Swap list
Go here and start fresh. Forget about your old password for the swap list. http://mailman.qth.net/mailman/listinfo/amswap 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jim Isbell, W5JAI Sent: Wednesday, March 05, 2008 1:20 PM To: Discussion of AM Radio in the Amateur Service Cc: [EMAIL PROTECTED] Subject: Re: [AMRadio] New AM Swap list Well, I was happy with the first subscribe, but now I cant figure out how to get subscribed again. When I go to the site in the first post on how to change settings it refuses my pasword??? On Wed, Mar 5, 2008 at 9:17 AM, A.R.S. - WA5AM [EMAIL PROTECTED] wrote: Tell u want I'll do guys. I'll delete all memberships from the AMSWAP list and let everyone subscribe manually. Thanks Guys!! On Wed, Mar 5, 2008 at 9:05 AM, Bob Bruno - K2KI [EMAIL PROTECTED] wrote: What's the old saying? You can please some of the people, some of the time, Most of the people, most of the time but you can never please all of the people, all of the time. :-) 73, cul... Bob de k2ki JT Croteau wrote: Good idea Brian, but I bet you are going to get a lot of flames from people who don't like to be automatically subscribed to reflectors. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail- archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. -- Money is only temporary, radios are forever - Jim Little aka the old dawg/K5BAI __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail- archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. -- Jim Isbell If you are not living on the edge, well then, you are just taking up too much space. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] {ADMIN NOTICE TO SELLERS AND BUYERS ON THIS LIST}
I normally don't like to get involved in this kind of thing but will put in
my 2 cents this time. I have to agree that it would be much simpler to have
the reflector set up with the reply to and reply to all to work like
most all other reflectors are set up. That, in my opinion, would solve most
of the problems.
I think this was debated long ago and it was decided that both replies
should go to the reflector so that the list doesn't miss anything. Well
this is what happens. Most people try to do the right thing, but don't
realize at the time what will happen.
I think the warnings about don't reply to ads on the list about equal the
number of violations. So that doesn't save much archive space either.
Concerning extra stuff getting on the list with these replies, It seems to
me that there is much more junk on the list about bashing the ARRL or
something else that seems to go on and on, compared to a few replies to for
sale items. Of course maybe that is what this list is destined for rather
than good AM discussions.
I about wear out the delete key with this junk and have come close to
unsubscribing from the list many times. The for sale replies are small
compared to the rest of the junk posts.
73
Gary K4FMX
-Original Message-
From: [EMAIL PROTECTED] [mailto:amradio-
[EMAIL PROTECTED] On Behalf Of Edward B Richards
Sent: Friday, February 29, 2008 10:49 AM
To: amradio@mailman.qth.net
Subject: Re: [AMRadio] {ADMIN NOTICE TO SELLERS AND BUYERS ON THIS LIST}
I am purposely sending this to the list so others see how I feel about
the situation. I am one of the sellers that use this reflector. About
once a month I post an ad for tubes or parts or equipment. I try to
comply with the rules but being human and old, I forget because this
reflector is different from the others I subscribe to. The other
reflectors go only to the person posting the message when you hit reply
. You have to hit reply all to post it to the reflector. Only this
reflector does it go to the list when you hit reply.
__
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the word unsubscribe in the message body.
[AMRadio] Watt meters
Don wrote: There is no such thing a an rf power meter, at least when we are talking about an instrument that most amateurs could afford. The so-called wattmeters are really rf voltmeters calibrated to the read the level of power delivered when the measured voltage is imposed across a known resistance. Most rf wattmeters are calibrated to work into a 50 or 72-ohm load. At any other load impedance, the reading is erroneous. While a true wattmeter is an absorption type of instrument, the wattmeters like the Bird and many other thru line meters measure voltage and current to determine power on the line. They will accurately measure at impedances other than 50 ohms too. You just subtract the amount of reflected power indicated from the forward power indicated for true forward power. It also doesn't matter if the load is reactive either as these type wattmeters will read true within their capability. 73 Gary K4FMX __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Re: MODULATION POWER REQUIRED
The waveform of the rf signal is not the same thing as the waveform of the envelope pattern of a modulated waveform. We could term this modulation power of the transmitter to distinguish it from PEP. When we talk about the average power output, or mean power output of a transmitter, we are talking about the average that is integrated over several cycles of the waveform of the audio that modulates the carrier. With PEP, you are selecting the one highest peak, which may occur infrequently, or possibly only once during the entire transmission, and basing your power output reading on the average rf power during that peak. This has very little to do with the apparent loudness of the signal, or the amount of interference it may generate. 73 Gary K4FMX __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Re: MODULATION POWER REQUIRED
The average VOLTAGE of a sine wave is meaningless. You don't use it to calculate average power. We are looking for the RMS value. The RF signal is always composed of sine waves no matter if there is modulation or no modulation. It also doesn't matter what the wave shape of the modulating signal is either, tones, voice or whatever, the RF coming out of the transmitter is still going to be sine waves. If it were not there would be serious harmonics generated. When we are talking about PEP and the average power over one or more cycles we are talking about the RF cycles of the transmitter. Each part of the audio envelope, even the narrowest peaks, are going to be composed of (contain) many RF cycles in each of those peaks. Being that all of those RF cycles are pure sine waves the rules of .707 times the peak voltage to find RMS voltage will always apply. The amplitude of those RF cycles will vary with the modulation envelope level. To measure PEP we pick a point that is the highest part of the modulation envelope (peak) and there will be many many pure RF sine waves contained there. We want to find the average power in those sine waves at that particular time. If you have a fast enough scope you can see exactly what is happening. Look at a transmitter modulated with a tone and you will see the familiar modulation envelope. Spread that way out by increasing the sweep speed and turn up the brightness and you will see all the RF cycles under the modulation envelope. Those are all pure sine waves and will always be. A 3.8 MHz signal with 1000 cycle modulation on it will show a 1000 cycle modulation envelope and contained in that envelope there will be 3800 RF cycles. You can break that down further and say that half of that audio envelope will be positive and half negative. So then the positive half will have 1900 RF cycles. We could break that down further and find how many cycles are near the peak if we wish. But the point is they are all RF cycles and good sine waves on which power is measured. If you are modulating the transmitter with speech the RF power still comes out in perfect sine waves regardless of the modulating waveform. If you were trying to measure audio power at the audio frequencies in this manner then it would not be pure sine waves with speech. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jim Candela Sent: Friday, February 15, 2008 9:54 AM To: amradio@mailman.qth.net Subject: [AMRadio] Re: MODULATION POWER REQUIRED Don, It seems that we have defined PEP power pretty well: Well, PEP is defined as the AVERAGE power over at least one RF cycle at the most powerful point of the envelope. Now, since we do not speak with sine waves, the average power point of the envelope is going to be less than 0.636 (sine wave average) of the peak value. With many voices the average might be 0.2 to 0.5 of the peak. Doesn't this mean we can increase the peak power until the PEP as we have defined it hits 1500 watts? It seems that many of us confuse peak power with Peak Envelope Power. The definitions are different. If I have this correct, then unprocessed voice peaks can be increased until the PEP legal limit is achieved, and the carrier level might be a lot more than 375 watts. Maybe the KW1, or Johnson Desk KW at Hi-Tap are still legal? Regards, Jim __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Modulation power required
MODULATION POWER REQUIRED Since the discussion the other day about reducing drive when using a linear amp seemed to have some interest maybe this will be of interest to some also. For a plate modulated final it is common thought that if you have a 100 watt input final amp that you need 50 watts of audio to modulate it 100%. But what does that really mean? You look at the modulator tube specs in the handbooks and they show how much power they will produce into a certain load. Start doing the math to figure out what that load is and things start to get a little fuzzy sometimes. Take a final that has 1000 volts and draws 100 mA. That is 100 watts input and common knowledge says that we need 50 watts of audio for 100% modulation. To find the load impedance we divide plate voltage by plate current so we have 1000/.1 = 1 ohms that the modulator is going to see. We know that the peak modulator voltage must match the final plate voltage for 100% modulation so lets do it that way first. With 1000 volts audio applied to the final from the modulation transformer (this is peak voltage) it is working into 1 ohms. To find the power required we do E squared /R. So we have 1000x1000=1,00 divide by R which is 1 ohms. That gives us 100 watts. Wait a minute!! Isnt it only supposed to take 50 watts to modulate that 100 watt final? Heres the thing that lots of people overlook: The 50 watts that is often quoted is AVERAGE audio power and that is talking about using a sin wave single tone. The peak power in a 50 watt sin wave signal is 2 times the average so all this works out. The point is that we must remember when we are figuring modulation voltage and power across the plate resistance that we are dealing with peak voltages and currents. The average power of a sin wave is going to be ½ that amount. When we say that a transmitters power output increases by 50% with modulation we are talking about average power of the modulation. A transmitter with 75 watts carrier (same as above with 75% efficiency) out will contain 37.5 watts total side band power so the total transmitter power out will increase to 112.5 watts with full modulation. But remember that this is with the transmitter modulated with a single tone sine wave audio power. Average voice power is going to be quite a bit less than that as average voice is anywhere from ¼ to something less than that. Now we get to PEP, peak envelope power. Remember our peak modulating voltage above shows that we need that voltage to be the same as the DC plate voltage for 100% modulation. That effectively doubles the plate voltage at the instant the audio sin wave is at its peak (peak audio voltage plus DC plate voltage). When plate voltage is doubled so does current get doubled. This makes for 4 times the power at the instant of the audio signal peak than what we had with just the carrier. Just as the peak modulation voltage is only there for the duration of the audio peak, so is the peak plate voltage there for that duration and so is the peak power there for the duration of the audio peak. That is where the PEP (peak envelope power) figure comes from. It is the power that is being generated during the peak (or crest) of the modulation signal (envelope). The PEP that we are concerned about is the output PEP of the transmitter and you can work it backwards if you observe the output power of the transmitter. Our same transmitter above that produced 75 watts carrier out and had a total side band power of 37.5 watts average will be used. You can not add powers together when figuring PEP; you must add the voltages first then calculate the power just as we did with the peak input power of the final in the above. But here is the catch! The Peak Envelope Power is the COMPOSITE of all the signals involved. That means the two individual side bands and the carrier. Just as these 3 components make up the familiar modulation envelope that we are used to looking at on the scope. --- 75 watts into 50 ohms has a voltage of square root of PxR. So the square root of 75x50= 61.2 volts. Now we find the voltage in EACH of the side bands: The total side band power is 37.5 watts so each side band will contain 18.75 watts. 18.75 watts into 50 ohms = 30.6 volts. Now we add all the voltages together: 30.6 + 30.6 + 61.2 = 122.4 total volts P = E squared /R. To find the PEP, 122.4 squared = 14982/50 ohms = 299.6 or rounded to 300 watts. 4 times the carrier power. We are using RMS voltages here rather than peak voltages. Shouldnt we be using peak voltages as we did in the plate circuit? Well, PEP is defined as the AVERAGE power over at least one audio envelope cycle. So we need to use the average power of the carrier at least. Average power is derived from RMS voltage so we use the RMS voltage of the carrier. With the side band part which represents the envelope we used the RMS voltage of each
RE: [AMRadio] Modulation power required
Thank you John! You are absolutely right. That should have been; at least one RF cycle at the peak of the audio envelope. That's what I thought I wrote but I guess the gremlins messed it up. :) What you are talking about, seeing it on a scope can be easily done as you describe if you have a fast enough scope and you trigger on the envelope. By expanding (using a faster sweep time) you can see each individual RF cycle under the audio envelope waveform. You will see many RF cycles for each audio cycle and see the different amplitudes of each RF cycle across the audio waveform. 73 Gary K4FMX -Original Message- From: John Coleman [mailto:[EMAIL PROTECTED] Sent: Thursday, February 14, 2008 4:56 PM To: [EMAIL PROTECTED]; 'Discussion of AM Radio in the Amateur Service' Subject: RE: [AMRadio] Modulation power required Perfectly and beautifully said Gary, except for one thing and some may not have caught it. I make this sort of mistake all the time so I'm glad I'm not the only one, HIHI. I hope you don't mind my adding in a little here just for clearing up a little detail. Original paragraph said: Well, PEP is defined as the AVERAGE power over at least one audio envelope cycle. So we need to use the average power of the carrier at least. Average power is derived from RMS voltage so we use the RMS voltage of the carrier. The above statement is defining the average power over one audio cycle would be the 2 sidebands power plus the carrier power as you said before. For PEP it should read: Well, PEP is defined as the AVERAGE power over at least one RF cycle at the most powerful point of the envelope. I have been asked this so many times so I feel compelled to expand on it. While looking at a envelope display on the scope and picking a place on the screen where the envelope is at the tallest peak then expand your scope horizontally to a mile wide display so as to see one or two RF wave forms at the place where the envelope peak was and measure the average power of the one or two RF waves at that point. Since we can't expand the scope to a mile wide display we must calculate the values as Gary said and imagine what we might see. John, WA5BXO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Modulation power required
-Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Bob Macklin Sent: Thursday, February 14, 2008 5:19 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Modulation power required Why not just calibrate a Trapezoid display for MAXIMUM PEP? The just watch the trapezoid display? Watching a single cycle on a scope is a difficult thing to do. HOW DO YOU AVERAGE PEP ON A SINGLE CYCLE? E squared / R will give average power. 73 Gary K4FMX __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Modulation power required
Bob, As John says it's just part of the definition of PEP that the FCC gives. I would suspect that their wording is meant to preclude anyone coming up with some creative ways to get around what they have in mind. They say it must be measured over at least one RF cycle. That means that you may measure as many cycles as you wish as long as you are measuring them at the peak or crest of the modulation envelope. The easiest way to measure PEP is to just measure the highest peak of the modulation envelope on your scope like John mentioned. You measure the peak to peak value, divide that in half for the peak value, multiply by .707 to give RMS, square that and divide by your load impedance (50 ohms). That gives you average power at the peak of the modulation wave form which is Peak Envelope Power. 73 Gary K4FMX -Original Message- From: Bob Macklin [mailto:[EMAIL PROTECTED] Sent: Thursday, February 14, 2008 6:33 PM To: [EMAIL PROTECTED]; Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Modulation power required E squared / R will give average power. So how do you do that on a single cycle? Bob Macklin K5MYJ Seattle, Wa, Real Radios Glow in the Dark - Original Message - From: Gary Schafer [EMAIL PROTECTED] To: 'Discussion of AM Radio in the Amateur Service' amradio@mailman.qth.net Sent: Thursday, February 14, 2008 3:13 PM Subject: RE: [AMRadio] Modulation power required -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Bob Macklin Sent: Thursday, February 14, 2008 5:19 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Modulation power required Why not just calibrate a Trapezoid display for MAXIMUM PEP? The just watch the trapezoid display? Watching a single cycle on a scope is a difficult thing to do. HOW DO YOU AVERAGE PEP ON A SINGLE CYCLE? E squared / R will give average power. 73 Gary K4FMX __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail- archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Using a Ranger as a driver
While it is true that for 100% modulation the modulation voltage must be equal to the final plate voltage. But it is also misleading to say that it is strictly a function of modulation voltage. If it were only voltage needed then we could use a very high step up ratio modulation transformer to accomplish modulation. The modulation transformer secondary works into a certain load impedance (resistance) supplied by the final plate circuit of the RF stage. While it is true that the modulation voltage must match the final plate voltage (for 100% modulation), it must also supply current to that load impedance in order to be able to produce that voltage. Voltage times that current equals power required of the modulator. After all, all of the side band power of the modulated signal comes from the modulator. If we have a transmitter that is not 100% modulated by a certain amount of audio power and we decrease the power of the RF stage the modulation power will remain the same but the modulation percentage will increase. By increasing the load impedance of the RF stage (by reducing its plate current) the modulation transformer can produce more modulation voltage because it is working into a higher load impedance. But if we don't turn down the modulation level the modulator will still produce the same amount of power that it did before. The difference is the voltage out will be higher and the current lower. This is assuming that the final is still not being over modulated. If we go too far at letting the modulation voltage rise on the RF stage by further reduction of the RF stage plate current we will run out of plate swing room on the modulator tubes. The impedance rise on the RF stage is reflected back to modulator tubes. When that happens clipping will occur in the modulator plates. At this point we would need to change the modulation transformer ratio so that the modulator tubes see a lower impedance to keep them operating within their plate current range. 73 Gary K4FMX OTOH, the modulator is looking at a load that is determined directly by The RF stage ratio of Ep/IP. For some reason most people look at modulator power as a determination of modulation percentage and this is some what misleading. It is really easier to just say that the peak audio voltage delivered by the modulator must equal or exceed the DC voltage on the final RF amp for 100% modulation. If the DC voltage is 600V on the RF class C final then the modulator must be capable of at least 600V peak or 1200 Volts peak to peak, because for 100 percent modulation the DC on the final must vary down to 0 Volts and up to twice the DC value. If a XMTR is unloaded to draw less plate current (Ip) the plate voltage will remain at the same voltage. If there is less current being pulled by the final but the voltage is the same then the Z seen by the modulator is higher than before. The higher resistance that the audio is looking into makes it easier to produce the needed voltage. It is easier for the one modulator (the same mod XFMR ratio) to modulate a 60 watt rig with 600V than a 100 watt rig with 600 Volts. Matching the impedance is not necessary. It is often confused with the statement that says when the load Z equals the source Z there will be maximum power transfer. This is a true statement. But power transfer is not the issue here. Getting the voltage on the final to swing from 0 to 2*DC with out distortion, that is the issue. Of course we won't to do that at a power level determined by our needs. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Using a Ranger as a driver
Yes Jeff, the peak voltage supplied by the modulator must be equal to the final plate voltage. The modulator voltage adds to the plate voltage to make the voltage double during positive modulation peaks. On negative modulation peaks the modulation voltage subtracts from the plate voltage making it go to zero. The peak to peak modulation voltage will be 2x plate voltage. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Geoff/W5OMR Sent: Wednesday, February 13, 2008 12:35 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] RE: Using a Ranger as a driver Gary Schafer wrote: While it is true that for 100% modulation the modulation voltage must be equal to the final plate voltage. No. Not equal to, but *twice* as much. 2*Ep But it is also misleading to say that it is strictly a function of modulation voltage. What other voltage is present at the plate (other than the DC supply voltage) if not for the AC voltage achieved by the modulator? High-level plate-modulation, we're talking about. The modulation transformer secondary works into a certain load impedance (resistance) supplied by the final plate circuit of the RF stage. While it is true that the modulation voltage must match the final plate voltage (for 100% modulation), 2*Ep. -- Driving your AM Rig without a scope, is like driving your car at night, without headlights. (K4KYV) -- 73 = Best Regards, -Geoff/W5OMR __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Using a Ranger as a driver
Yes of course you are right John. I tried to simplify the power out of the modulator explanation but didn't do too well. The modulator power does drop off as its load impedance is increased. Percentage of modulation increases with the square of power increase. So 50% modulation requires only 1/4 the power that 100% requires. 73 Gary K4FMX -Original Message- From: John Coleman [mailto:[EMAIL PROTECTED] Sent: Wednesday, February 13, 2008 1:19 PM To: [EMAIL PROTECTED]; 'Discussion of AM Radio in the Amateur Service' Subject: RE: [AMRadio] RE: Using a Ranger as a driver Yes more than voltage is required; current from the modulator is also required. The amount of current depends on the EP/IP ratio of the final. So as the final is loaded heavier for more IP then the modulator will be required to produce more current as well as the previously required voltage for 100% modulation. If the RF Final is tuned for less current the Modulator will also reduce its audio current output while the audio voltage rises. But the current will reduce faster than the voltage increases so that the modulation power is actually less even though the rig may now be over modulated. This can be proven by setting the modulation to about 50% with a tone, then make note of the modulator current of the class B modulators. Now while the rig is modulating, putting power into a dummy load, reduce Ip of the final by re-tuning a little till the current is about 50%. Note the modulation percentage level on the scope has increased and the class B modulators are drawing less current. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Wednesday, February 13, 2008 11:20 AM To: 'Discussion of AM Radio in the Amateur Service' Subject: RE: [AMRadio] RE: Using a Ranger as a driver While it is true that for 100% modulation the modulation voltage must be equal to the final plate voltage. But it is also misleading to say that it is strictly a function of modulation voltage. If it were only voltage needed then we could use a very high step up ratio modulation transformer to accomplish modulation. The modulation transformer secondary works into a certain load impedance (resistance) supplied by the final plate circuit of the RF stage. While it is true that the modulation voltage must match the final plate voltage (for 100% modulation), it must also supply current to that load impedance in order to be able to produce that voltage. Voltage times that current equals power required of the modulator. After all, all of the side band power of the modulated signal comes from the modulator. If we have a transmitter that is not 100% modulated by a certain amount of audio power and we decrease the power of the RF stage the modulation power will remain the same but the modulation percentage will increase. By increasing the load impedance of the RF stage (by reducing its plate current) the modulation transformer can produce more modulation voltage because it is working into a higher load impedance. But if we don't turn down the modulation level the modulator will still produce the same amount of power that it did before. The difference is the voltage out will be higher and the current lower. This is assuming that the final is still not being over modulated. If we go too far at letting the modulation voltage rise on the RF stage by further reduction of the RF stage plate current we will run out of plate swing room on the modulator tubes. The impedance rise on the RF stage is reflected back to modulator tubes. When that happens clipping will occur in the modulator plates. At this point we would need to change the modulation transformer ratio so that the modulator tubes see a lower impedance to keep them operating within their plate current range. 73 Gary K4FMX OTOH, the modulator is looking at a load that is determined directly by The RF stage ratio of Ep/IP. For some reason most people look at modulator power as a determination of modulation percentage and this is some what misleading. It is really easier to just say that the peak audio voltage delivered by the modulator must equal or exceed the DC voltage on the final RF amp for 100% modulation. If the DC voltage is 600V on the RF class C final then the modulator must be capable of at least 600V peak or 1200 Volts peak to peak, because for 100 percent modulation the DC on the final must vary down to 0 Volts and up to twice the DC value. If a XMTR is unloaded to draw less plate current (Ip) the plate voltage will remain at the same voltage. If there is less current being pulled by the final but the voltage is the same then the Z seen by the modulator is higher than before. The higher resistance that the audio is looking into makes it easier to produce the needed voltage. It is easier
RE: [AMRadio] RE: Using a Ranger as a driver
Hi Jim, I think what John is saying is that you do NOT want to retune when you lower the plate voltage in order to maintain the same plate impedance. If you were to half the plate voltage with a modification to the transmitter then during tune up you would want to tune up to half the plate current that you had with full voltage before the modification. That will give you the same plate load impedance and the modulator tubes will see the same impedance. You are now operating at 1/4 the power you were when you had twice the plate voltage. But maintaining the same load impedance on the modulator is not necessarily important: See below. When reducing power by reducing screen voltage the plate voltage is going to remain the same and plate current is going to be less, so the plate impedance will be higher and the modulator will see a higher impedance also. Now the modulator will not be able to produce as much power as it did before because the modulator plates will flat top (go into limiting) with the lighter load on them. That is if you try to pull the same amount of audio out of them as you did before when they were working into the lower load impedance. But this is not a bad thing because with reduced power in the final you don't need as much audio to modulate it with. The load impedance that the modulator tubes see is not important as long as it is low enough to be able to produce enough power to fully modulate the transmitter before the modulator tubes voltage swings to the saturation point. If the load impedance is too low the tubes will work too hard trying to produce enough power out and will operate in the non linear part of the plate curve. Some transmitters are deliberately designed to have the modulator tubes flat top and act as limiters to keep the modulation percentage below 100%. The venerable Johnson Viking 2 is such an example. The modulation transformer that they chose provides a little too high a load impedance to the modulator tubes so that they go into clipping before 100% modulation is achieved. Their idea of a soft clipper. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jim Wilhite Sent: Tuesday, February 12, 2008 10:00 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] RE: Using a Ranger as a driver Ok John, I have but a few observations and questions that might steer everyone through this. I am having trouble understanding how the Z the modulator see is greater if the plate load impedance goes down. If the Plate Z is = to the Ep divide by 2 times the Ip and you change one value how does the Z remain the same. Even if you maintain the same ratio doesn't the plate Z change as a result? In your example you change both at the same ration which maintains the same impedance. Ep 600 Ip200 ma. Zp= 600 divided by 2 times .2 = 600/.4 = 1500 Ep300 Ip100 ma. Zp = 300 divided by 2 times .1 = 300/.2 = 1500 The ratios stay the same, but what I question is if you reduce the plate voltage of a tube but load it to the same value of Ip or near it, the impedance changes on the secondary of the mod transformer, which I guess, is where the divide is. I have seen many people make this mistake. Because if you do, to maximize power or whatever reason, the impedance seen by the primary of the mod transformer is not optimum. In the discussion of the way to drive the amplifier no one pointed out that you must maintain the ratio of Ep to Ip. This is where I kept sticking. Now the question becomes, why did Johnson say to load the Ranger to rated plate voltage and current but insert the pad between the transmitter and amplifier? Just guessing here, but I would bet that amateurs of the 50s were much like those of today. All knobs and stated reading must be to the right. Or is there something that is seen on the primary of the mod transformer by the Class A or B modulator tubes we haven't discussed yet? Jim/W5JO Hi Jim, What I said was, or tried to say, when a Class C rig is unloaded so as to draw less current, that is, to tune the loading and plate circuit so that the plate dip is lower current than it was when it is tune up for max. The plate voltage will stay about the same but the plate current is less and you have less RF output as well of course. In this scenario the ratio of Ep / Ip is greater. The Z that the modulator sees is greater. Now if the plate voltage is lowered with out retuning anything, the plate current will fall as the plate voltage falls and the ratio of the two remains the same. Basically when a class C rig is set and not retuned, the Ep:Ip ratio is set and the plate current should follow the plate voltage up and down linearly. The RF should follow the plate voltage up and down as well. Some tubes and circuits need a little help with this. Such as using grid
RE: [AMRadio] Re: Carrier with one sideband
Nice display Jim! But put it in the double side band position and reduce the carrier to -60 db or so and notice that you have exactly the same wave form as that of the SSB with carrier at -6db, which is equal to the side band energy in this case. It is not the transmission of the single side band with carrier that gives the distortion but the envelope detector in the receiver. With only one side band and carrier the detector can't make up its mind which signal is supposed to be the carrier and which is the modulation when you have higher levels of modulation. The result is high levels of second harmonic distortion generated in the detector. As long as the modulation percentage is kept to a lower level the distortion is minimal and it sounds fine. If you use a receiver with a rather sharp filter and listen to a regular AM signal and tune off to one side (which is often done when heavy qrm is present) you generate the same kind of signal at the detector in your receiver. You greatly reduce one side band of the signal reaching the detector and it sees SSB with carrier. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jim Tonne Sent: Thursday, February 07, 2008 7:48 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Re: Carrier with one sideband Gents: First, this is my first post to this interesting group and I hope you take what I have to say constructively. This business of SSB on AM, etc., is of interest to me on a technical basis. But let's do a computer simulation of this thing. To this end I have written a computer program which allows you to select various AM modes and the program then shows you the transmitted envelope and the associated spectrum. It is temporarily posted here: http://tonnesoftware.com/ModTutor.exe That file is just a barefoot executable without all of the usual Window$ garbage. It should run on most Windows computers. If not e-mail me and I'll make a full-blown install routine. I am suggesting you download the program and run it. Click on the opening screen option Single sideband and then click on Ideal lower sideband. See the transmitter output as a carrier. Then click on Carrier= 0 dB. Then on Carrier=-6 dB. Then on Carrier=-12 dB. Not real pretty, is it? Now click on Double sideband and on Carrier=0 dB. I think the folks on this group will find the routine as interesting as others have. - Jim WB6BLD __ Our Main Website: http://www.amfone.net AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Halli HT37 Phasing Mod problem
If you are trying to align it using a tone and looking for a flat response on the scope and you have any hum in the circuit you will never get it aligned. Hum can come from poor filter caps in the power supply or audio leads picking it up. The best way that I have found to align phasing rigs is to talk into the mike while listening to the opposite side band and tune things for minimum (best side band suppression). A nice long ooh works good. You will need to switch side bands and do the same on the other as they interact. You can tune it for really great suppression on one side band while the other one won't be so great. Find the point where the suppression is nearly equal on each side band while listening to the opposite side. Sometimes the Rf phasing coil will have little effect when tuning it. It depends on how tightly it is coupled to the next stage. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, November 27, 2007 11:59 AM To: amradio@mailman.qth.net Subject: [AMRadio] Halli HT37 Phasing Mod problem Hello, I have been trying to get this like new HT37 on the air for awhile. The audio phasing modulator has been near impossible to properly ballance espeially using the manual instructions. So far have replaced a leaky low pf brown drop silver mica that corrected some of the problem but still am not able to get a properly phased output from the modulator. The audio seems ok up up to the rf stage where it won't align. The carrier osc is on freq ok but the carrier phasing adjustments do not work out. Where would be a good location to apply a ballanced audio signal to bypass most of the original circuit?. Has anyone come up with an alignment procedure using modern test gear? Thanks, Bill, KB3DKS/1 __ Our Main Website: http://www.amfone.net AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] 51J3 price
Can someone tell me what a 51J3 is going for these days? One was donated to our club and they would like to sell it to raise funds for some projects. The 51J3 is in very nice condition. Has top and bottom covers. Thanks for the help. Gary K4FMX __ Our Main Website: http://www.amfone.net AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Re: GB AM vs SSB???
-Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Bob Macklin Sent: Friday, April 06, 2007 11:52 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Re: GB AM vs SSB??? RBethman comments: As to SSB, the KWS-1 IS fine. As to AM - It transmits a carrier and ONLY one SIDEBAND. Thereby being POOR for DSB with carrier since it ONLY O-N-E sideband with CARRIER. This is the same way the video portion of a TV signal has been transmitted for over 50 years! What is wrong with SSB-AM? Vestigial SB? Bob Macklin K5MYJ Near Seattle, Wa Wow! There sure seems to be a lot of SSB bashing going on here lately. Some of you guys sound like some of the unwashed SSB guys that bash AM. Just reverse the AM and SSB words and you couldn't tell the difference! Seems to me all would be better off sticking to the facts rather than inventing stuff to bolster your preferred points. SSB AM is not as good as full DSB AM but it is also not as poor as some believe it is. A properly set up SSB AM rig can sound pretty good. Modulation level does have to be kept down some as Don says or the receiver detector distortion goes up rapidly as you approach full modulation. As you near 100% modulation the receiver detector can't tell the difference between the carrier and the modulation signal. Second harmonic distortion results. When I say set up properly, there are few that know how to do that right. Most that run SSB rigs on AM, in the DSB with carrier mode have a hard time making them sound good on AM and it is mostly the fault of not setting it up properly. Some sound very nice. Want to see what good SSB AM sounds like? Just tune off to the side of a good sounding AM signal with your receiver so that the filter cuts one side band off but not enough to reduce the carrier. The audio level will drop a little and distortion may rise slightly but it will still sound pretty good. You are hearing the same thing as if it was transmitted with only one side band. This same trick is often done when there is heavy qrm on one side. You listen to SSB AM and don't even realize it! As to Collins S line receivers sounding better than some of the rice box receivers, I haven't heard one. I have several 75S-1, 75S-3, 75S3A etc. receivers. All have more distortion than my Kenwood TS430. I measured each with a distortion analyzer, and you can hear the difference, and the TS430 runs rings around any of the Collins receivers in audio quality. So just because it's old doesn't readily mean that it is better. 73 Gary K4FMX __ AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] THE VIKING II AND FRIED HAM
It is a good idea to use a separate fuse for the high voltage and the low voltage. With one fuse only you can have a short on the low voltage and it will cook the low voltage transformer and never blow the fuse. BTDT. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, March 28, 2007 5:52 PM To: [EMAIL PROTECTED] Cc: amradio@mailman.qth.net Subject: Re: [AMRadio] THE VIKING II AND FRIED HAM The internal fuse in the Viking II is in line with the low and high voltage transformer primaries and protects both. As stated before, there is no prorection for the antenna relay socket unless the original fused line plug is used. This is not a good idea and it should be replaced as you said, with internal fuses. If wired correctly, only one additional fuse would be needed to protect both sides of the line and the lead to the relay socket should be moved ahead of the fuse to protect that outlet. 73, John, W4AWM I replaced the single internal fuseholder with a double one and used the second holder for a single fuse in the hot side of the line only and replaced the line cord with a 3 conductor and 3 prong prang. ** See what's free at http://www.aol.com. __ AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Low modulation
Just a note about work bench tops if you happen to be doing this high voltage testing on the bench. Some bench top surfaces like kitchen cabinet counter tops that are made of formica are very conductive! Be careful. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of D. Chester Sent: Monday, February 19, 2007 11:24 AM To: amradio@mailman.qth.net Subject: Re:[AMRadio] Low modulation To test the modulation transformer for sure, try high voltage a.c. on it. The insulation may be breaking down at higher voltage, while appearing normal at 110 v.a.c. __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Tranny Test
You had best have something to protect that microameter when you turn on the supply as the capacitance of the transformer windings will look like a short to the meter until the charge equalizes. Running it up with a variac would be ok. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of John Lawson Sent: Monday, February 19, 2007 3:38 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Tranny Test Re: quasi-pseudo hi-pot testing of your transformer - if you have a device that produces the required 800-1000 VDC - and can access that voltage (such as a bench supply, one of the other power supplies in the transmitter - or even a Ranger maybe) then [carefully!] attach the positive lead of that source to the windings (tie the leads toggether) thru a suitable microammeter and ground the tranny frame... any leakage will show up on the microammeter. A panel-mount 0-20 uA DC meter, mounted on a piece of plastic, will do. If you use a DVM - just insulate it well - put it in series - don't let any part of it get near ground or you - set the meter, step back - turn on the HV - check the reading. Shouldn't be very many microamps to ground. Note that any significant ripple, or other AC disturbances, in the HV source, will confuse the reading, due to capacitive and inductive coupling of those components. Use 'pure' DC. Remember to tie the transformer HV leads together - the object is to measure any current flow from the body of the windings, thru the insulation, to the frame - NOT from one side of the winding to the other - which would only be a few ohms DC resistance. Cheers John KB6SCO DM09fg __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Megger
There are different types of meggers. You may be better off with a hi-pot tester. http://www.somis.org/BVT.html 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Rick Brashear Sent: Tuesday, February 13, 2007 11:59 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Megger Brian, I'll use it to test transformers, chokes, etc. I am asking about the right instrument? No doubt, I am as green as a gourd on this one. Thanks, Rick What are you going to use it for Rick? __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] test
Test ___ Amradio mailing list List Home: http://w5ami.net/mailman/listinfo/amradio_w5ami.net Partner Website: http://www.amfone.net Post: mailto:Amradio@w5ami.net
Re: [AMRadio] test
Hi Jim, Testing my patience with the computer! Trying to figure out how to edit the address history file for the send to in outlook. Can't figure out how to add or delete an address from it. Whenever I send something to someone it automatically adds the address but I don't know how to do it otherwise. 73 Gary K4FMX _ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Wilhite Sent: Thursday, January 04, 2007 10:21 PM To: Discussion of AM Radio Subject: Re: [AMRadio] test Blood test, drug test, breathing test or driving test? Hi Gary: Jim W5JO From: Gary mailto:[EMAIL PROTECTED] Schafer Test ___ Amradio mailing list List Home: http://w5ami.net/mailman/listinfo/amradio_w5ami.net Partner Website: http://www.amfone.net Post: mailto:Amradio@w5ami.net
RE: [AMRadio] PEP for AM
P E P (AM) % Modulation = (( PEP - PC) / PC) *100% Example: Carrier Power PC = 100 W, PEP = 400 W. Determine % Modulation M% = (( 400 - 100) / 100) *100% = ((20-10) / 10) *100% = 100% Hmmm, let's see, 400 watts -100 watts = 300 watts. Divided by 100 watts = 3. Times 100% = 300% modulation.. I think they forgot the square root of the powers in the formula. Looks like that may add to the misconception. But I'm not sure they left out the square root symbol. Could that be the reason for the double parentheses on the left? Since most word processing programs do not have easy access to mathematical symbols, and e-mail programs may not have them at all, a special set of symbols has evolved for mathematical expressions. I am not totally familiar with them, and I sometimes get totally lost when trying to interpret mathematical expressions posted over the internet. Isn't this what the formula is supposed to look like? (the problem is that it may not display correctly if your e-mail reader does not support Unicode). ______ % Modulation = ( vPEP - vPC ) / (vPC) *100% Evidently they think that so few people would have a use for mathematical formulae that maths symbols are not included in the default character set. Just like the ricebox manufacturers who no longer include monitor scopes in their appliance product line. Don k4kyv This is how it should be. % Modulation = (( vPEP - vPC) / vPC) *100% They had the parenthesis correct but didn't have the square root signs. You need the double parenthesis at the front as there are two opposite ones following. They must all balance. You perform the functions within the inner set first then do what is in the next set, then do what is outside last. I cut and pasted your square root symbols for this. Can someone tell me how to do square root symbols on a regular keyboard? 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] PEP for AM
-Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Geoff/W5OMR Sent: Friday, December 29, 2006 4:42 PM To: Discussion of AM Radio Subject: [AMRadio] PEP for AM Anyway, I ran across this information, and thought I'd share it with the group here, so that some mis-conceptions about AM PEP could be cleared up. (from: http://www.pc-oscilloscopes.com/articles/pc_oscilloscope_rf.html) P E P (AM) % Modulation = (( PEP - PC) / PC) *100% Example: Carrier Power PC = 100 W, PEP = 400 W. Determine % Modulation M% = (( 400 - 100) / 100) *100% = ((20-10) / 10) *100% = 100% -- 73 = Best Regards, -Geoff/W5OMR Hmmm, let's see, 400 watts -100 watts = 300 watts. Divided by 100 watts = 3. Times 100% = 300% modulation.. I think they forgot the square root of the powers in the formula. 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] HV Wire
Coax works fine for HV leads. I have an 813 amp with around 2500 volts that I have had a piece of rg58 on for years. I have a commercial lab 15Kv supply that has a modified pl259 and rg8 cable coming out of it. Ground the shield and if it should arc it will only arc to ground. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Mike Sawyer Sent: Friday, December 22, 2006 3:16 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] HV Wire I'm with Bill on this one. Braided copper can be purchased as a sheath for HV lines. Coax, you really don't have a good idea of what the insides look like. Mod-U-Lator, Mike(y) W3SLK I don't have personal experience (and don't want any), but have heard horror stories regarding the use of coaxial cable as high voltage wire. Short answer: Don't do it! Use fresh cable designed for the purpose. If you are willing to experiment with a potentially lethal configuration, at least route the wire away from any exposed surfaces. If it does let go at least it won't be through you. 73 de Bill, AB6MT [EMAIL PROTECTED] __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Odd signals in lower 80 meters
I haven't listened on 80 for those signals but I have herd similar to what you describe in the past. A few years ago there were several companies selling scramblers that inverted the audio. A lot of them went into South America and were used by people for their private radio networks. I would guess many were not licensed users. You can not decode it by switching side bands. It is simply done by mixing the speech with an audio tone and everything comes out upside down. The high frequencies come out as low frequencies and the low frequencies come out at high frequencies and they are offset by the mixing tone frequency. If you listen carefully you can make out a word once in awhile. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of A.R.S. - W5AMI Sent: Tuesday, December 19, 2006 12:05 PM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] Odd signals in lower 80 meters Has anyone beside Don/KYV and myself heard these odd sounding voice signals between 3700 and about 3750 that seem to be sideband, but can not be tuned in either lower or upper sideband? They seem to be all over the place, however no one else has said a thing about them except Don on amfone.net. They sound like inverted audio, however it would seem that going to the opposite sideband would allow you to tune them, but it doesn't. Maybe I'm not thinking clearly on Inverted audio. If not, would someone straighten me out? I started a thread on another list, and it's as if no one has heard them, and I am now getting the feeling I'm losing my marbles! 73 Brian / w5ami -- There is nothing more uncommon than common sense. -- Frank Lloyd Wright __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] No Code Pros and Cons
Well Speaking as the guy who actually brought up the 'dumbing-down' issue in this thread - I'd like to posit a Thought on the issue of no-code ham license vs. IQ. For all those that think that the code is a big part of being a knowledgeable ham keep this in mind: In the past in the military electronics schools a person that washed out of the electronics classes was sent to be a high speed CW operator. 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] No Code Pros and Cons
-Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Anthony W. DePrato Sent: Saturday, December 16, 2006 9:39 PM To: [EMAIL PROTECTED]; Discussion of AM Radio in the Amateur Service Subject: RE: [AMRadio] No Code Pros and Cons For all those that think that the code is a big part of being a knowledgeable ham keep this in mind: In the past in the military electronics schools a person that washed out of the electronics classes was sent to be a high speed CW operator. 73 Gary K4FMX SNIP Gary: what military are you talking about Navy did not do that. the Marines were given guns and sent to a rifle squad. sailors were sent to electrical school at least that was what happened back in the 60's 73 Tony Air force. 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Screen Modulated 813
The 813 and 572 are tubes that should never show color. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jim Wilhite Sent: Monday, December 11, 2006 12:24 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Screen Modulated 813 You are most correct John, I was speaking of power tubes not the lesser cousins. I didn't make that clear but in light of the subject, I plead not guilty. Jim W5JO - Original Message - From: John Lawson [EMAIL PROTECTED] To: Discussion of AM Radio in the Amateur Service amradio@mailman.qth.net Sent: Monday, December 11, 2006 10:35 AM Subject: Re: [AMRadio] Screen Modulated 813 On Mon, 11 Dec 2006, Jim Wilhite wrote: Yes, but we in the amateur service do not even consider running them at the max. Red is ok if you take into consideration all parameters and follow design considerations. Dave Knepper also writes: The reason that the tube is a bit cherry red is to continually remove built-up gasses inside the tube. There is a wealth of practical, hands-on - and also theoretical, knowledge available on this List - a rarity among reflectors to be sure. Jim has provided myself and many others with constant 'good information' regarding AM transmitting gear. But but but but: Speaking as a design engineer, lifelong tube-geek, and (moderately succesful) thermionic designer - I would like to make the point that plate incandescance may, or may not, be 'OK' depends on the device amd the regime it's run in. Unless designed for such dissipation, it is most certainly NOT OK to run many tubes at a blush. The venerable 6146 is a case in point - running the plates red in a 6146 alters them irreversibly and generally kills 'em... get a 'fresh' one, test it for Gm, run it good and red for a while, then re-test. ooops There are of course tubes designed to run red, even bright yellow - like the various radiation-cooled tubes - IIRC 4-65s, etc... There are some tubes, like the 833, that can stand a little color and not get terribly upset. Running plates red does not, in most cases, re-adsorb gasses - if anything it facilitates thier release - depends entirely on the plate alloy, thickness, and any coating, element spacing, grid material and design, spacer materials, etc., etc.. You can't just make generic generalizations like this... the situation is way more complex. Red plates also has implications for permanent grid damage - not to mention that fact that we want that plate to collect electrons, not emit a bunch of them... ;} And as for running them to the max - all tubes have a point of maximum 'efficiency' where the power transfer function is optimal. Is the plate red at that place under the curves? If it's a radiation-cooled tube, you bet. If it's a 6146 - it just died. And just who is the we you speak of? ;} I run my Valiant on the raggedy edge most of the time - and I've chewed up one brand new set of finals finding out just where that edge is... d'oh! But now I know just how to get the max out of the transmitter and still keep the Output Devices happy - even if I do make 'em sweat good and hard... Anyway - the study of the theory and design of vacuum tubes is pretty damn fascinating to me - and if anyone is interested, I have a fairly comprehensive bibliography on the subject that I'd be happy to post, if there is any interest. And seeing as how most of us are using power tubes, and building / operating devices using power tubes - might save some bucks in the long run. Just my 200 millidollar for a Monday Morning... Cheers and Best of the Season John KB6SCO DM09fg __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Screen Modulated 813
The 811A should show a barely perceptible red color at maximum dissipation (per the RCA tube manual). The 30L-1 pushes the tubes a little beyond their limits. Add a little speech processing and they get pushed even harder. 73 Gary K4FMX -Original Message- From: david knepper [mailto:[EMAIL PROTECTED] Sent: Monday, December 11, 2006 2:09 PM To: [EMAIL PROTECTED]; Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Screen Modulated 813 Did you ever know that the 811A's in the Collins 30L-1 do show color under modulation? If any one of the four tubes does not, then, that tube should be replaced. An 813 normally does not show color, unless the plate is the metal variety and not the carbon plate. I would agree that this tube should operate without any blushing whatsoever. Dave, W3ST Publisher of the Collins Journal Secretary to the Collins Radio Association www.collinsra.com - the CRA Website Now with PayPal CRA Nets: 3.805 Mhz every Monday at 8 PM EST and 14.253 Mhz every Saturday at 12 Noon EST Collins Chatroom - Daily at 4 PM EST on 14.285 Mhz - Original Message - From: Gary Schafer [EMAIL PROTECTED] To: 'Discussion of AM Radio in the Amateur Service' amradio@mailman.qth.net Sent: Monday, December 11, 2006 1:34 PM Subject: RE: [AMRadio] Screen Modulated 813 The 813 and 572 are tubes that should never show color. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jim Wilhite Sent: Monday, December 11, 2006 12:24 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Screen Modulated 813 You are most correct John, I was speaking of power tubes not the lesser cousins. I didn't make that clear but in light of the subject, I plead not guilty. Jim W5JO - Original Message - From: John Lawson [EMAIL PROTECTED] To: Discussion of AM Radio in the Amateur Service amradio@mailman.qth.net Sent: Monday, December 11, 2006 10:35 AM Subject: Re: [AMRadio] Screen Modulated 813 On Mon, 11 Dec 2006, Jim Wilhite wrote: Yes, but we in the amateur service do not even consider running them at the max. Red is ok if you take into consideration all parameters and follow design considerations. Dave Knepper also writes: The reason that the tube is a bit cherry red is to continually remove built-up gasses inside the tube. There is a wealth of practical, hands-on - and also theoretical, knowledge available on this List - a rarity among reflectors to be sure. Jim has provided myself and many others with constant 'good information' regarding AM transmitting gear. But but but but: Speaking as a design engineer, lifelong tube-geek, and (moderately succesful) thermionic designer - I would like to make the point that plate incandescance may, or may not, be 'OK' depends on the device amd the regime it's run in. Unless designed for such dissipation, it is most certainly NOT OK to run many tubes at a blush. The venerable 6146 is a case in point - running the plates red in a 6146 alters them irreversibly and generally kills 'em... get a 'fresh' one, test it for Gm, run it good and red for a while, then re-test. ooops There are of course tubes designed to run red, even bright yellow - like the various radiation-cooled tubes - IIRC 4-65s, etc... There are some tubes, like the 833, that can stand a little color and not get terribly upset. Running plates red does not, in most cases, re-adsorb gasses - if anything it facilitates thier release - depends entirely on the plate alloy, thickness, and any coating, element spacing, grid material and design, spacer materials, etc., etc.. You can't just make generic generalizations like this... the situation is way more complex. Red plates also has implications for permanent grid damage - not to mention that fact that we want that plate to collect electrons, not emit a bunch of them... ;} And as for running them to the max - all tubes have a point of maximum 'efficiency' where the power transfer function is optimal. Is the plate red at that place under the curves? If it's a radiation-cooled tube, you bet. If it's a 6146 - it just died. And just who is the we you speak of? ;} I run my Valiant on the raggedy edge most of the time - and I've chewed up one brand new set of finals finding out just where that edge is... d'oh! But now I know just how to get the max out of the transmitter and still keep the Output Devices happy - even if I do make 'em sweat good and hard... Anyway - the study of the theory and design of vacuum tubes is pretty damn fascinating to me - and if anyone is interested, I have a fairly comprehensive bibliography on the subject
RE: [AMRadio] Re: Pw Supply
I am not so sure the correct answer was given and there was no explanation of why two separate transformers would not work other than the primary current seemed higher. It seems this would make a much better topic to argue about than some other recent ones. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of ne1s Sent: Thursday, December 07, 2006 1:20 PM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] Re: Pw Supply Hi Jack, See comments/answers below. 73/GL, -Larry/NE1S Jack Schmidling writes: MFJ has a 900v one for about $100. Is there any reason why I can not use two of these and tie one side of the secondaries together and call that the center tap and have an 1800v ct transformer/s? Jim Candela has already given the correct answer (no), and why. __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Re: Pw Supply
See below.. -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Geoff/W5OMR Sent: Thursday, December 07, 2006 4:48 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Re: Pw Supply Gary Schafer wrote: I am not so sure the correct answer was given and there was no explanation of why two separate transformers would not work other than the primary current seemed higher. It seems this would make a much better topic to argue about than some other recent ones. You didn't see Jim's post? That's not what he said. We needed 60 volts CT at 200 amperes with 208 vac primary. The secondary isolation from the primary had to withstand 200,000 volts DC. The core was a large 'C' core, and the whole thing sat in a oil tank. The layered layers of mylar insulation resulted in considerable leakage inductance within the transformer. Before we built the beast we tried two 30 volt @ 100 ampere standard transformers to power up a big electro-magnet. It worked but the primary I was 2X what it should have been. Maybe the Tripplett clamp on ammeter was miss-behaving from the every half cycle current draw, but I also recall blowing circuit breakers, and darkening portions of the building. The boss was concerned to say the least. After building the 60v CT transformer prototype, everything worked fine, and had expected primary current. So was it core saturation from high DC current one way only, a power factor issue, or something else? I really don't know, and since that was 1981, my recall could be put in question. After all , over 50 now, so CRS is a fact of being an OM! ;-) I had to make a 0-200amp DC linear series regulator for that supply. A large water cooled heatsink and 32 TO-3 2N6258's in parallel. What a monster that was! I don't have a good reason as to why, either. I can't explain to you why the primary current of two power supplies doubles, when the output of the two supplies are in series. Meaning, I draw 3 amps from the power supply, when running 1500v @ 300mA on the final, and the modulator biased off at 150mA (0v bias @ 1500v), but if I turn on the second supply, and bias the modulator back to 150mA (with 2700v instead of 1500v) the primary current on the two supplies jumps from 3 to around 8.5 or 9amps. 'Splain that one? -- 73 = Best Regards, -Geoff/W5OMR -- Maybe I picked the wrong subject to get an argument going. :) Except for Geoff no one else seems up for it. :) Anyway, I did a little reading about two transformers with secondary's in series and it seems that when you do that and use a full wave rectifier, that each transformer acts like a half wave circuit and there is a DC current in the winding (because it is pulsating DC) which tends to saturate the core of the transformer. So it seems that one of Jim's assumptions was correct. Now if you put two transformer secondary's in series and use a BRIDGE rectifier you don't have the core saturation problem because there is no DC in the individual cores. Current flows both ways in each transformer over the full cycle. - Geoff, on you problem with current increasing from what I can glean from your post you double the voltage and set the modulator current to the same as it was with lower voltage. That = more watts so more current in the primary. Different problem than transformers in series. 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Ranger Audio... the numbers
It's beginning to sound like a partially shorted mod transformer. With 20 volts signal on the grids of the mod tubes I would think that you should see at least 200 volts on the plates?? Could be bad 6L6's. The reason that you see a slightly distorted audio pattern on the audio amplifiers when in tx and not in standby could be the result of the negative feedback loop trying to correct distortion from the mod transformer. Can you easily get high modulator plate current with audio applied? Will the mod plate meter peg or nearly so if you hit it hard? If it will that is an indication that the tubes are good and the transformer may be shorted. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jack Schmidling Sent: Friday, November 17, 2006 9:45 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Ranger Audio... the numbers Gary Schafer wrote: Check at the center tap of the mod driver transformer with your scope and see if you see anything there. Could be a bad or missing bypass cap there. It's brand new but I didn't have a 15mf so I used a 47mf.. ditto for C59A. Check the jumpers on the plug in the back to be sure that the proper taps on the mod transformer are selected. All ok. Check the clamp tube circuit. Could be holding the screen slightly low on the 6146 and clipping the modulation peaks to the screen. Screen voltage is 150 and the nom is 190. However, R35, the Modulator Screen Voltage Adjustment resistor seems to go to the clamp circuit and it is not at all clear what is going on here. It seems to me that diddling with it changes the screen voltage on the 6146. So does diddling with the modulator current effect the 6146 screen voltage or do I have a screen voltage problem? Check modulator screen voltage. It is the nominal 250V... but again, why is it nominal if that resistor is there to diddle with the current? js -- PHOTO OF THE WEEK: http://schmidling.com/pow.htm Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Ranger Audio... the numbers
Plate to plate impedance on the 6L6's is going to be in the neighborhood of 5000 to 6000 ohms. 400 volts plate to plate voltage swing would be around 26 watts of audio. Plate voltage swing to ground would be 1/2 the above or around 200 volts to ground for 1 tube. Since there is about 26 volts of bias on the grids the peak grid voltage at greater than 26 volts will cause grid current to start to flow and the tubes will be slightly into AB2 operation, which I think they do get into. I believe you measured around 20 volts on the grid to ground so it is in the ball park. But the plate voltage swing seems awfully low. It is difficult to detect a shorted modulation transformer sometimes. As Larry says it is hard to detect shorted turns by measuring with an ohmmeter. I once had a mod transformer that looked ok at low signal levels and resistance measurements looked fine. But when a small amount of audio power was applied it would break down and short. Look at the grids again when applying audio and see if the peak voltage reaches the bias voltage. Also put the scope on the center tap of the driver transformer and DC couple it and see if you see any movement when applying audio. That will be an indication of grid current being drawn. Then if you still have only 50 volts on the plates of the mod tubes-- something is amiss. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jack Schmidling Sent: Friday, November 17, 2006 5:50 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Ranger Audio... the numbers Larry Taft wrote: Just from rule of thumb for audio tube amps you should get a couple hundred volts audio swing (not related to BIRD WATTS) at each plate to ground. 50 v is only a couple of watts audio. Could you explain the math on that? How do you arrive at watts knowing only volts? As a data point, 50v into a 50 ohm load is 50Watts js -- PHOTO OF THE WEEK: http://schmidling.com/pow.htm Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Ranger Modulation
You can't reverse the plate leads on the modulator tubes because it uses negative feedback from a winding on the transformer. Reversing the plate leads puts the feed back in phase rather than out of phase. It will oscillate! First check to see that you have proper grid current on the 6146. Low grid current will not allow full positive peak modulation because the tube runs out of steam with low drive. It is much more important to have proper grid current with AM than it is with cw. The tube has to have enough emission to handle the peak power 4x the carrier. Be sure the screen voltage is high enough on the 6146. Be sure that you are not overloaded - more power than the transmitter is rated for. If you have it loaded too heavy again the tube runs out of emission and will not allow the modulation peaks to go high enough. Try another 6146. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jack Schmidling Sent: Thursday, November 16, 2006 10:28 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Ranger Modulation Larry Taft wrote: Try reversing the phase of the audio by swapping the output leads of the modulation xfmr. First I swapped the tubes to no avail. I then swapped the wires and now have a strange buzzing that I can not locate but it shows up on the audio with the gain at zero. Don't know if I barfed something up or not but I vaguely remember reading somewhere that this an an indication to reverse the leads. Weak tube in the audio chain causing lack of gain needed for the positive peak. Just ordered new audio tubes. Now I notice another discrepancy. the manual that came with it says to adjust the mod current to 75-90 ma. The manual that Rick sent me for the new version which I seem to have says 55-70 and no clue why the difference. Which is correct and should I make an allowance for using 6L6's instead of 1614's? js -- PHOTO OF THE WEEK: http://schmidling.com/pow.htm Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Ranger Modulation
-Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Larry Taft Sent: Thursday, November 16, 2006 11:06 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Ranger Modulation Well, I tried...I wasn't right so now I'll be left Sorry about the bad info. 73, Larry K2LT Better to be wrong sometimes than to never try. Wish I had a nickel for every time I was wrong. That's the value of posting to the list, everyone learns. 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Ranger Audio... the numbers
-Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jack Schmidling Sent: Thursday, November 16, 2006 10:02 PM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] Ranger Audio... the numbers I can not do a freq response test because I do not have a proper sig gen. Mine is a cheap step job and the amplitude is all over the place. I put a 1khz sine wave into an earphone sitting on the mic and measured p-p values with a scope Pin 2 V7A (grid) 5mv Pin 7 V7b (plate)50 mv Pin 2 V8 grid. 3 v Pin 1 V8 plate.. 40 v Pin 5 V9/10 grid 20 v Pin 3 V9/10 plate... 10 v (standby) Pin 3 ... 50 v I assume that where the voltages dropped it had something to do with the transformer being across the output and the standby more for the mods. I all cases, the amplitude dropped a bit and the sine wave got a little bent when going from stdby to phone. It flattened out slightly. In the case of the grids of the mods.. a great deal of distortion was seen when in the phone mode. Only an approximation of a sine wave with jagged festoons all over. None of this was seen when looking at the plates in the phone mode. So, what can we make of this? js Check at the center tap of the mod driver transformer with your scope and see if you see anything there. Could be a bad or missing bypass cap there. You could be driving the modulators into too much grid current and causing the bias to shift around. Check the jumpers on the plug in the back to be sure that the proper taps on the mod transformer are selected. Check the clamp tube circuit. Could be holding the screen slightly low on the 6146 and clipping the modulation peaks to the screen. Check modulator screen voltage. 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Ranger Power
Or you could just reduce the loading with a 6146 in place and do the same thing. You end up with the same plate load impedance either way. No free lunch. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jack Schmidling Sent: Sunday, November 12, 2006 2:33 PM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] Ranger Power Had a most interesting conversation with Steve W8TOW. Among other things, he offered another and really cool way to reduce the power of the Ranger without violating any rules. Replace the 6146 with a 2E26, reduce the grid current to 2ma and Voila! 15 watts. js -- PHOTO OF THE WEEK: http://schmidling.com/pow.htm Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Re: Ranger... good news, bad news
I have never had a ranger hooked to an SB200 but it sounds to me that 12 to 15 watts is not enough drive for it. The SB200 has a gain of about 6 if I remember right. That means that 100 watts of drive will give 600 watts output. If you want 125 watts carrier output that requires the amp be capable of 500 watts output for peak audio. 500 watts output divided by 6 = 83 watts PEP. Divide that by 4 and that says that you need around 20 watts carrier. Working that the other way says that 20 watts carrier drive times 6 (the amplification factor of the amp) = 120 watts carrier out. So unless you have some higher gain tubes in the amp 12 to 15 watts drive will not be enough drive. Now you can tune and load the amp to get the 125 watts out with lower drive but it won't be linear. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of ne1s Sent: Wednesday, November 08, 2006 10:53 AM To: Discussion of AM Radio in the Amateur Service Subject: [AMRadio] Re: Ranger... good news, bad news Jack Schmidling writes: I tried the accessory plug mod as suggested, removing 2/6 and putting a meter across 2/4 and it works but the power is less than useful. It less than 5 watts and would only modulate about 25%. Did I do something wrong? It sounds like you did it right - there's not much to screw up. Maybe the Ranger has a problem. I get about 12W out from that connection. My Ranger power supply is not stock, but the voltages are pretty close. However, 15W is what I hear reported from others who have done this. It helps to reduce the grid drive a bit in the low power mode - adjust the drive pot for maximum RF out of the Ranger - but it won't make the difference between 5W and 12W out. And you should have absolutely no problem modulating to 100% positive and beyond if your audio is phased correctly and the modulator is working correctly; especially using the low power mod where you should have plenty of audio power to spare. How much RF carrier do you get out of the Ranger when operating normally, and are you able to modulate 100% then? 73, -Larry/NE1S __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Re: Ranger... good news, bad news
-Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jack Schmidling Sent: Friday, December 08, 2006 11:43 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Re: Ranger... good news, bad news Gary Schafer wrote: So unless you have some higher gain tubes in the amp 12 to 15 watts drive will not be enough drive. Now you can tune and load the amp to get the 125 watts out with lower drive but it won't be linear. Now I am really getting confused. I have contended all along that it takes about 20w drive. Everything seems to work well including 100% mod when I drive with 20w. Only problem being that the tubes redden. As a point of interest, I am using 6L6's in the modulator but assume they just won't last as long and not effect the amount of modulation. Is this a good assumption? js Here's how you figure how much the tubes will handle; In linear AM operation the efficiency of the amplifier has to be exactly half of what it is for SSB. This means that if you tune up the amplifier to 500 watts output and the efficiency is 66% (typical of a GG amplifier) and will handle 500 watts PEP output. For AM operation you would reduce the carrier to 125 watts output (down from the 500 watts at tune up) and not touch the tuning of the amp. This will drop the efficiency exactly in half or down to 33% in this case. So with 125 watts output at 33% efficiency you can find out what the input power to the amp is (should be) by dividing 125 watts by 33%. That gives 378.8 watts input. Now if you subtract the 125 watts from the 378.8 watts you will have the amount of power that the tubes need to dissipate or get rid of in heat. 378.8 watts minus 125 = 253.8 watts of plate dissipation. You subtract the output power because it is going out to the antenna, the amount left is dissipated in heat. 253.8 watts plate dissipation for two tubes is 126.9 watts per tube. If I remember right the plate dissipation ratting on the 572B is 125 watts so you are right at the maximum for the tubes. Now when you modulate the power output increases and so does the efficiency of the amplifier (to 66% on voice peaks) so the amount of power dissipated in the plates goes down slightly. If the tubes are getting red in a short time either the tubes are soft or things are not tuned up right. ** Figure out what the input power to the amp is by multiplying plate voltage by plate current and take 33% of that. It should come out to the power output fairly close. Or figure the efficiency by dividing output power by plate input power and see if it works out to around 33%. If not tuning is not correct. 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
FW: [AMRadio] Ranger... good news, bad news
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jack Schmidling Sent: Thursday, December 07, 2006 5:49 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Ranger... good news, bad news Gary Schafer wrote: If you want to run 125 watts carrier out of the SB200 on AM that means you need to tune the amplifier up for 500 watts or a little more output with the load and plate tune controls on the amp peaked for maximum output with a given amount of drive. Not sure I understand the why of this. I did all as you suggested but found when I was done that the plate tuning of the amp was exactly the same as if I tuned it originally with the 100w carrier. The dip was exactly in the same place and the loading optimum is so broad that no change could be noted. Watching the scope on the output of the amplifier should show the modulation peak voltage double what the carrier voltage is on the scope. If it doesn't you haven't tuned up properly. Interestingly, the only way I get the peak voltage to double is with the ricebox. I can never seem to get more than about 50% increase with modulation. js The peak envelope power of an AM signal increases by 4 times over the carrier power with 100% modulation. The linear amplifier must be tuned at the peak envelope power level or the peaks will never reach full power, the amplifier will flat top and splatter and you will not sound good. How much drive power did you have when tuning up the amp? Were you using a rice box to tune the amp or the ranger? If you don't see the scope voltage double with modulation you haven't tuned up right. If you adjust the scope to say 2 centimeters with carrier then the modulation peaks should hit 4 centimeters. 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Ranger... good news, bad news
Put a T connector on the output rf connector and put a capacitor on one side of the T. 73 Gary K4FMX As for my SB200 with a carrier only output of 75 watts the tubes will show a little color after ten minutes. I would like to drive the SB200 harder and unload the output to dip the plate at a lower level but there is not enough output capacitance on 75 meters to do this. Perhaps a switched in extra load capacitor would do the trick? Maybe it would be easier to just build a chassis with a pair of 6146s or 807s running class C with 50 ohm dummy load at the control grid instead of a tuned circuit and just have the plate circuit tuned. I may have just talked myself into something!! John, WA5BXO __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Ranger... good news, bad news
I am not sure that you are really tuning up as you describe but if so you will be flat toping quite seriously. Using a ranger or other AM transmitter with a linear amp requires the amplifier be tuned up with full modulation on the ranger with reduced power out of the ranger watching a scope at the output of the amplifier. It does not have enough carrier at full power to properly drive the SB200 and tune it properly. The easiest/best way to find out how much drive the amplifier needs is to use your rice box first. If you want to run 125 watts carrier out of the SB200 on AM that means you need to tune the amplifier up for 500 watts or a little more output with the load and plate tune controls on the amp peaked for maximum output with a given amount of drive. That drive will be around 80 to 100 watts. Try 80 watts of carrier from the rice box and peak the output of the amp for maximum output. If you can't quite get the 500 watts out increase the drive slightly and re-peak the amplifier tune and load. NOW reduce the drive until you have 125 watts out of the SB200 and MEASURE the drive power required to produce the 125 watts out of the amplifier and DO NOT TOUCH THE TUNING ON THE AMP! The amount of drive that you measured is the amount of carrier you will need from a ranger or other AM rig to drive the amplifier properly. No more no less! If you want to tune up the amp with the ranger driving the amp it needs to be done with full modulation of the ranger and a scope connected to the output of the amplifier. The first thing you need to do is find out how many peak volts on the scope represents 500 watts out of the amplifier. This is done easier with a rice box used as a driver first to establish the 500 watt level on the scope. Once you have that you can connect the ranger as a driver. Tune the amplifier up for maximum peak output, full modulation on the ranger with a tone or voice, watching the scope. Adjust the carrier output of the ranger so that you do not get much over 500 watts peak out of the amplifier. Readjust the tune and load controls on the amplifier for maximum output after each adjustment of the carrier out of the ranger. Always be sure that you are near 100% modulation and not going over on the negative side. Reducing the modulation to zero should yield a carrier right around 125 watts if you tuned everything right. That will allow the modulation peaks to go to 500 watts peak and the amp will be loaded properly. If you don't get 125 watts or near out you haven't tuned up properly. It is very difficult to tune this combination properly as drive is hard to adjust easily. It is much easier to use the rice box first to establish the parameters. Watching the scope on the output of the amplifier should show the modulation peak voltage double what the carrier voltage is on the scope. If it doesn't you haven't tuned up properly. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Peter Markavage Sent: Monday, November 06, 2006 12:56 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] Ranger... good news, bad news I see no reason to dip and load the SB-200 since it's a linear amplifier. When I do use the Ranger as a driver, at low power using my screen voltage adjustable control, it's initially run into a dummy load to get the approximate knob settings (dip and load, etc.) for the frequency of interest. Then it's switched into the input of the SB-200. SB-200 is tuned for maximum output while viewing an inline wattmeter. If output power is above 125 watts, I just back down the screen control on the Ranger and also check and/or adjust plate and load for resonance on the Ranger(generally minor touching up). You might also want to check your input circuits on the SB-200. The tuned input on 75M for my SB-200 was centered around 10 MHz and on 10M, it was centered around 40MHz. After diddling with the input capacitance values, I was able to get those bands fairly close to where they should be. Check out the info on this web site: http://www.ne7x.com/sb200/heathkit-sb200.htm With the solid state rigs it's even easier. Push the button for AM, back down on the RF drive, key down with the SB-200 and quickly tune for max. On a good day, SB-200 tune for max can be done in less than 10 seconds. FYI: Scope always hangs on the SB-200 output to watch for any perky RF or audio anomolies. Pete, wa2cwa __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
[AMRadio] Properly tuning a linear amplifier on AM
I should have re-titled the subject for this. Using a ranger or other AM transmitter with a linear amp requires the amplifier be tuned up with full modulation on the ranger with reduced power out of the ranger watching a scope at the output of the amplifier. It does not have enough carrier at full power to properly drive the SB200 and tune it properly. The easiest/best way to find out how much drive the amplifier needs is to use your rice box first. If you want to run 125 watts carrier out of the SB200 on AM that means you need to tune the amplifier up for 500 watts or a little more output with the load and plate tune controls on the amp peaked for maximum output with a given amount of drive. That drive will be around 80 to 100 watts. Try 80 watts of carrier from the rice box and peak the output of the amp for maximum output. If you can't quite get the 500 watts out increase the drive slightly and re-peak the amplifier tune and load. NOW reduce the drive until you have 125 watts out of the SB200 and MEASURE the drive power required to produce the 125 watts out of the amplifier and DO NOT TOUCH THE TUNING ON THE AMP! The amount of drive that you measured is the amount of carrier you will need from a ranger or other AM rig to drive the amplifier properly. No more no less! If you want to tune up the amp with the ranger driving the amp it needs to be done with full modulation of the ranger and a scope connected to the output of the amplifier. The first thing you need to do is find out how many peak volts on the scope represents 500 watts out of the amplifier. This is done easier with a rice box used as a driver first to establish the 500 watt level on the scope. Once you have that you can connect the ranger as a driver. Tune the amplifier up for maximum peak output, full modulation on the ranger with a tone or voice, watching the scope. Adjust the carrier output of the ranger so that you do not get much over 500 watts peak out of the amplifier. Readjust the tune and load controls on the amplifier for maximum output after each adjustment of the carrier out of the ranger. Always be sure that you are near 100% modulation and not going over on the negative side. Reducing the modulation to zero should yield a carrier right around 125 watts if you tuned everything right. That will allow the modulation peaks to go to 500 watts peak and the amp will be loaded properly. If you don't get 125 watts or near out you haven't tuned up properly. It is very difficult to tune this combination properly as drive is hard to adjust easily. It is much easier to use the rice box first to establish the parameters. Watching the scope on the output of the amplifier should show the modulation peak voltage double what the carrier voltage is on the scope. If it doesn't you haven't tuned up properly. 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Ranger... good news, bad news
-Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jack Schmidling Sent: Saturday, November 04, 2006 10:04 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Ranger... good news, bad news Mike Sawyer wrote: Now let me ask you a question Jack: Do you intend to use the Ranger as a driver for the RF and the audio section as a speech amp for a bigger modulator? Not at this point. I just want to drive the SB200 and get at least as much out of it as I do with the TS420 and be able to watch tubes glow. js If the tubes glow in an SB200 you are running them too hard. 73 Gary K4FMX __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Ranger... good news, bad news
John, Are you peaking the output circuit on the SB200 after you reduce the drive? If you are just using carrier out of it to drive the grid of the next amp you should peak everything to get maximum efficiency. Efficiency should be near 60% even at the low power level if you retune the plate circuit. 73 Gary K4FMX I have used the SB200 on AM and it does OK but I would not want to do it for a long time. Those tubes get real hot. I use the SB200 as a driver for my big rig. The input to the SB200 is about 5 - 10 watts and the output of the SB200 is about 50 - 70 watts carrier this drives the grid of my big class C plate modulated final. But even using the SB200 to put out 50 - 70 watts it get real hot and the tube show some color. I think the best thing I can do to increase the efficiency of the SB200 at low power, is to reduce the plate voltage to about 1500 instead of 2500. I added a switch to the front panel of mine to increase the bias voltage making it harder to drive. I thought that this would decrease the conduction angle enough to reduce the heat but the trouble is that the plate is still not reaching saturation at the low power level so I figure that if I reduce the plate supply voltage and increase the drive then I can come closer to the non linear class C service for continuous CW and the efficiency will surly increase. The idea is to use the rice box rig at low power so it will last a long time and have the SB200 to make up the slack. But I want it to last a long time as well. BJ and I like the flexibility of this type of operation. That is to be able to flip some switches and use the SB200 as linier on SSB as it was intended and then flip the switches back so as to lower the output but raise the efficiency for continuous carrier operation as required by the big class C final. We have been operating it linearly with the 2500 volts supply and reducing the drive from the rice box carrier source but it has always bothered me that it is so inefficient and those tubes show color. As I recall the PS in the SB200 is a voltage double type circuit perhaps a little circuit change up with some HV switches might be in order here? Any Ideas on this? John, WA5BXO __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Octal Sockets.... more Ranger stuff
If you haven't done so already look in the tube manual at the tube that goes into that socket. Some tubes have more than one pin connection for the cathode. As an example, tubes with a suppressor grid sometimes have that grid run to a pin and also an internal connection between the suppressor and cathode, with the cathode going to a pin on the socket also. That effectively leaves the cathode with two pins on the socket. Sometimes the manufacturer will chose one or the other pins on the socket as the cathode pin. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jack Schmidling Sent: Sunday, October 22, 2006 8:27 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Octal Sockets more Ranger stuff Jim Wilhite wrote: Just takes a little work. There is a tang that holds the pins in place. Just straighten it to get the lock past the shoulder and push the pin out with a tube or sharp pointed pick. Do you pull out from the bottom or push up and pull from the top? js -- PHOTO OF THE WEEK: http://schmidling.com/pow.htm Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Antenna Idea and lightning precautions
A square plate buried in the ground makes a poor ground for lightning. Lightning is dissipated in a sphere around a ground rod. The longer the rod the larger the sphere of dissipation. Length is what is important, not surface area. On the other hand too long a rod does little good either. As length increases so does inductance. Going down 20 feet with a ground rod will do nothing more than an 8 foot rod will do unless the soil is very dry and non conductive. It is much better to use several 8 foot or so rods spaced by the sum of their lengths. (16 foot spacing for two 8 foot rods). This is because the sphere of dissipation around the rods will overlap and not be as effective if placed closer. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jim candela Sent: Saturday, August 05, 2006 5:15 PM To: Mike Dorworth, K4XM; Discussion of AM Radio Subject: RE: [AMRadio] Antenna Idea and lightning precautions Mike, Thanks for the comments on this topic. At this point I am trying to get an idea on what to do, and how to calm the XYL about lightning. I still think erring on safety is the way to go, and mount my antenna elsewhere away from the house. That way I can disconnect the coax, and move the ends apart 20' or so. Still, the tower on the roof idea has technical merit. Heck millions of folks had TV antenna's on their roofs before cable or satellite TV was popular. It was a rare installation that was properly grounded, and yet even rarer when there was a lightning strike to the antenna. I was 'googling' around on the topic, and I ran into this neat sight: http://www.lightningrod.com/ This is for DIY lightning protection systems for the home, and they provide the parts, and guidelines on what you need. I see some Ham radio uses for these parts, like the 2 square foot copper ground plate instead of a ground rod. I notice that their 15/32 diameter copper wire is un-insulated. Now If I cut down that tree in the back that provides late afternoon shade for my neighbor (not for me), and also rains dead leaves into my pool, and replace it with a tower and an antennamy neighbor's wife will lynch me!!! She had a fit last year when I trimmed that same tree (on my property), and trimmed a few branches of her tree that hanged over my property. Both trees ar 40' plus Live Oak's. That was after I told her husband the day before what I was going to do. Apparently he isn't the one wearing pants in that household! :-) Jim JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Mike Dorworth, K4XM Sent: Saturday, August 05, 2006 2:59 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Antenna Idea and lightning precautions I can see this is the beginning of a long thread since everyone has their own ideas. In commercial work a sharpened spike above the thing to be protected is to DRAW the lightning to a well insulated and very well grounded ground system. This is to protect the equipment below it. To dissipate, the ball should be rounded like a car radio antenna to gently discharge the corona. We put up a series of 150 foot towers at work with a 21 foot stainless sharpened lightning spike above the tower top to draw the lightning. All of our ( 92 each) microwave towers had a 3 or four inch diameter sharpened brass rod 2 feet above the tip top of the tower. It's ground cable was insulated from the tower all the way down. Of course the tower and all the guys were also grounded to the common ground. A dipole can easily discharge static build up with a 100 k ohm resistor of at least 1 fourth watt. This keeps the system equalized. Lightning usually hit the HIGHEST ( though noy always) spot, so if there are taller trees they would get it first. I like insulated wire instead of bare since the damp wind will not build up thousands of volts when it blows over..just before a storm. For fun take the antenna connector and put in a mason jar and place near ground and watch the 4 inch long blue firs just before a storm on a hilltop. A Johnson Matchbox sounds like a fourth of July celebration if left connected. I guess, in the end a direct strike is bad news in every case. Most of us are really talking about big static discharges I think. A real strike will blow every receptacle in the house out and the wire on on side of every power cord will vaporize and the fuse box will be blown off the wall. Let the tall trees take that!.. 73 Mike - Original Message - From: Jim candela [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Saturday, August 05, 2006 2:36 PM Subject: [AMRadio] Antenna Idea and lightning precautions Hi All, I am contemplating putting up an inverted Vee antenna where the center point is above my house suspended with a 30' Lowes push up mast attached to my
RE: [AMRadio] Antenna Idea and lightning precautions
Hi Mike, While the sharp pointed rods are ok at the top of the towers to try and make them the place where lightning strikes first, the insulated down lead is not a good idea. It is better to connect the lightning rod directly to the tower. The tower will have much less inductance than the down lead that is supposed to carry the strike current. The chances of an arc over from the down lead to the tower are great because of the high inductance of the lead. Voltages can become very high on it. Also the down lead will induce current into the tower and coax lines running down the tower anyway. So there is nothing to be gained by the insulated down lead except higher cost and the invitation to an arc somewhere you don't want it. This is why it is recommended for all cables on the tower to be bonded at several intervals along the length of the tower, to prevent voltage differences between cables and tower. A ball or rounded end type lightning rod does not bleed off energy but prevents corona so that early streamers do not form as they do from pointed rods. A real strike is survivable with no damage if things are properly protected and grounded. It happens many times on many many installations. There is always the possibility for damage to occur but it is rare on good installations. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Mike Dorworth, K4XM Sent: Saturday, August 05, 2006 2:59 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Antenna Idea and lightning precautions I can see this is the beginning of a long thread since everyone has their own ideas. In commercial work a sharpened spike above the thing to be protected is to DRAW the lightning to a well insulated and very well grounded ground system. This is to protect the equipment below it. To dissipate, the ball should be rounded like a car radio antenna to gently discharge the corona. We put up a series of 150 foot towers at work with a 21 foot stainless sharpened lightning spike above the tower top to draw the lightning. All of our ( 92 each) microwave towers had a 3 or four inch diameter sharpened brass rod 2 feet above the tip top of the tower. It's ground cable was insulated from the tower all the way down. Of course the tower and all the guys were also grounded to the common ground. A dipole can easily discharge static build up with a 100 k ohm resistor of at least 1 fourth watt. This keeps the system equalized. Lightning usually hit the HIGHEST ( though noy always) spot, so if there are taller trees they would get it first. I like insulated wire instead of bare since the damp wind will not build up thousands of volts when it blows over..just before a storm. For fun take the antenna connector and put in a mason jar and place near ground and watch the 4 inch long blue firs just before a storm on a hilltop. A Johnson Matchbox sounds like a fourth of July celebration if left connected. I guess, in the end a direct strike is bad news in every case. Most of us are really talking about big static discharges I think. A real strike will blow every receptacle in the house out and the wire on on side of every power cord will vaporize and the fuse box will be blown off the wall. Let the tall trees take that!.. 73 Mike - Original Message - From: Jim candela [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Saturday, August 05, 2006 2:36 PM Subject: [AMRadio] Antenna Idea and lightning precautions Hi All, I am contemplating putting up an inverted Vee antenna where the center point is above my house suspended with a 30' Lowes push up mast attached to my roof with a tripod mast base made for roof mounting. This would make the apex at almost 50', and with the trees around my home, the ends at about 30'. Other locations that I might have the antenna apex at will be densely surrounded by trees, and I am trying to avoid that. My question is about lighting concerns with this approach. I would have multiple 12 awg ground straps from the mast base to earth ground via copper ground stakes at least 5' long. This would act as a counterpoise for the antenna, and provide a DC ground reference for the 30' mast. My fear is that the antenna would attract a lightning hit (direct) and that would cause my home to burn up in a flaming fireball. Then I was thinking about how lightning rods work, and when done properly, don't lightning rods work by having a sharp point at the tip, where they bleed the static (a corona discharge) to prevent a lightning strike? If so, why can't I take a 1/8 stainless 8' whip with a point on top, mounted above the inverted Vee apex, and use that as a lightning rod? I guess I'd need to beef up my ground wiring scheme just in case of a direct hit. Any suggestions? I am hoping for having more lightning protection with my
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
RE: [AMRadio] Replies, duplicates, and so on
While I like the list in its current configuration, I do see how it could be annoying to get duplicates sent to both the list and the original poster(s). Having just done this to Gary and Geoff, from now on I'll try to remedy this and send only to the list. Old habits die hard. Sorry Geoff/Gary. ~ Todd, KA1KAQ While it is true that a reply will also go to the sender as well as the list I don't consider it to be a big problem. Sometimes it is an advantage as it may take hours for a reply to get through the list (at times). It is easy to delete the extra reply that comes in unless you happen to be one who is posting constantly then you get lots of duplicates. :) 73 Gary K4FMX
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] 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] 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] 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 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post:
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] 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. The
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
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' amradio@mailman.qth.net 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
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] 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 amradio@mailman.qth.net 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] 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] 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
[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 amradio@mailman.qth.net; Discussion of AM Radio amradio@mailman.qth.net 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] 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 amradio@mailman.qth.net; Discussion of AM Radio amradio@mailman.qth.net 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
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 amradio@mailman.qth.net 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] 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] 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 outboard mic preamp? If so, what were the results, please? Many thanks and 73, Craig W3CRR
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] 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 amradio@mailman.qth.net; [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 displayed conductivity on BOTH sides of each diode...not good. Is this the reult of transients / voltage spikes somehow overwhelming the diodes...? It used to
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 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
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] 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] 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 BW 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 amradio@mailman.qth.net 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] 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 BW 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] 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] 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 amradio@mailman.qth.net 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
