RE: [AMRadio] Home Brew AM Transmitter Wanted
Building is a LOT of work, but fun. If you was to ask me, there is not a lot out there for a reasonable price that is not homebrew and is worth a crap. 30K1, KW1, T368 BC610, Johnson kilowatt, old broadcast TX. It's a shame I am so attached to my homebrew stuff or I would sell it and build more. A pair of 813's at 2000 or so volts does real well, about 600 watts out. A pair of 812a's or 811a's does about 300 watts easy, and with 811a modulators is a simple stable rig. The 4-125/250/400 need 3000 volts or more to be real happy, and that is a stress on some parts. The hard parts to get seem to be high voltage variable capacitors, high power switches, old plug in coils that have not turned to dust, high voltage oil filled caps, and big iron. On my last transmitter, I wound a pie net coil using copper tubing. Finding lots of nice looking matching meters is hard. I must have huge amounts of money and time in my homebrew rigs, and I cant imagine selling them for any reasonable price and being happy about it. I sold my 30K-1 and did not worry about it. On the other hand, I have seen homebrew stuff at ham fests that they would have to pay me to take... Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of W5OMR/Geoff > Sent: Tuesday, March 28, 2006 11:44 AM > To: Discussion of AM Radio > Subject: Re: [AMRadio] Home Brew AM Transmitter Wanted > > Bob Maser wrote: > > > Anyone out there have a well constructed home brew AM > transmitter that > > is laying around collecting dust? I am looking for one that runs > > 350-1000W out and can be fully integrated or one that uses a driver > > for the RF and modulator. If you have one that you would > be willing > > to part with, give me a call at 813-643-3034 or E Mail me. > > > > Thanks for reading >
Re: [AMRadio] Home Brew AM Transmitter Wanted
Bob Maser wrote: Anyone out there have a well constructed home brew AM transmitter that is laying around collecting dust? I am looking for one that runs 350-1000W out and can be fully integrated or one that uses a driver for the RF and modulator. If you have one that you would be willing to part with, give me a call at 813-643-3034 or E Mail me. Thanks for reading Hey, Bob.. why not just build one? I'm sure that somewhere here on the list, you could probably find all the parts and tubes you need to build your own. I'm sure that there are some people here that would nearly give you the parts, just to encourage another home-brewing ham. You could probably run a single 450TH/L, 304TH/L ... how about an 813 in the final, modulated by a pair of 811's? The only problem you might have is finding the iron/transformers. But, it never hurts to ask ;-) -- 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?
RE: [AMRadio] Home brew AM
Patrick, That Altec amplifier sure is nice! I really like the 5R4 full wave bridge rectifier with the extra filament taps off the HV windings. Never seen that done before. Also the 6W6 triode connected cathode follower stage is unique with the center tapped choke. I see negative feedback from the output tranny all the way back to the first preamp stage. Without getting too far into audio jargon, how do two of these beasts sound as a stereo amplifier? The HV filter only has 6 uf as part of a LC filter, so how is the bass response? Got a few dozen of these lying around? :) Regards, Jim Candela WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Patrick Jankowiak Sent: Monday, October 04, 2004 7:32 PM To: amradio@mailman.qth.net; [EMAIL PROTECTED] Subject: Re: [AMRadio] Home brew AM I would say that the fidelity was pretty good compared to a BC-610, mostly because the audio amplifier was of exceptional quality and so lightly loaded. The power at carrier was pretty low, only about 80 watts, and when we were done tweeking, we were getting about a 340 watt PEP signal out of it. Running the power low, with low voltage and current allowed the rare tube to stay cool. As for power, I imagine the BC-610's carrier is much more powerful. The modulator amplifier is rated at 175 watts and is an Altec 1570B, using two 811A's in class B push pull with the grids driven directly from cathodes of some beam power tubes, the schematic of this unit is here: http://www.soundpractices.com/altec.html It has 10 tubes, and operates with 930VDC on the 811A's. I use two of these amps in my stereo. best regards, Patrick From: "Brian Carling" <[EMAIL PROTECTED]> Subject: Re: [AMRadio] Home brew AM How does that compare to the performance of say the 250TH final stage in a BC-610? It sounds like you are running at lower power. Also how many tubes do you use in the cathode modulator? On 2 Oct 2004 at 20:12, Patrick Jankowiak wrote: >> Cathode mod works very well on a 250TH. We are getting 80-90 >> watts carrier no problem at 2200V. For the details: >> >> http://www.montagar.com/~patj/cathmod01.htm >> >> >> Patrick __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net --- Incoming mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.772 / Virus Database: 519 - Release Date: 10/1/2004 --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.772 / Virus Database: 519 - Release Date: 10/1/2004
Re: [AMRadio] Home brew AM
I would say that the fidelity was pretty good compared to a BC-610, mostly because the audio amplifier was of exceptional quality and so lightly loaded. The power at carrier was pretty low, only about 80 watts, and when we were done tweeking, we were getting about a 340 watt PEP signal out of it. Running the power low, with low voltage and current allowed the rare tube to stay cool. As for power, I imagine the BC-610's carrier is much more powerful. The modulator amplifier is rated at 175 watts and is an Altec 1570B, using two 811A's in class B push pull with the grids driven directly from cathodes of some beam power tubes, the schematic of this unit is here: http://www.soundpractices.com/altec.html It has 10 tubes, and operates with 930VDC on the 811A's. I use two of these amps in my stereo. best regards, Patrick From: "Brian Carling" <[EMAIL PROTECTED]> Subject: Re: [AMRadio] Home brew AM How does that compare to the performance of say the 250TH final stage in a BC-610? It sounds like you are running at lower power. Also how many tubes do you use in the cathode modulator? On 2 Oct 2004 at 20:12, Patrick Jankowiak wrote: >> Cathode mod works very well on a 250TH. We are getting 80-90 >> watts carrier no problem at 2200V. For the details: >> >> http://www.montagar.com/~patj/cathmod01.htm >> >> >> Patrick
Re: [AMRadio] Home brew AM Cathode modualtion
I appreciate all of the suggestions. I'm not locked into a particular tube configuration yet, but I have to admit there is something appealing about running the 450TH. It's probably my mental image of two of them lit up behind a glass window in the front panel :) Clay W7CE - Original Message - From: "John Coleman, ARS WA5BXO" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Sunday, October 03, 2004 12:37 PM Subject: RE: [AMRadio] Home brew AM Cathode modualtion > The "Rice" neutralization circuit works better with a higher Q > grid tank and, if possible, some input swamping or grid load resistor. > The biggest trouble with the circuit is that the loading of the grid > tank is not constant over the full RF cycle as a result the "Q" and > balance is shifted somewhat over the period of the RF cycle. Starting > with a higher "Q" or C value is one way of minimizing this effect. > > The circuit does work because I used it as well and also with a 304TLs, > back in the days of experimenting with the ultra modulation or balanced > high level modulation circuits. I eventually went to standard "Push > Pull". > > John, WA5BXO > > > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Donald Chester > Sent: Sunday, October 03, 2004 12:45 PM > To: amradio@mailman.qth.net > Subject: RE: [AMRadio] Home brew AM Cathode modualtion > > > >The 450th is a big triode, so I don't think you can run it single ended > pie > >net output, you would need to do 2 250th tubes in push pull or > something, > >but the 450th would do the cathode modulator quite well. > > > You could use a single-ended pi-network type output circuit, with a > balanced > grid tank coil. That is knows as "Rice" neutralisation. You don't get > as > perfect null as you can with a balanced plate tank cincuit or a pushpull > > arrangement, but it works well enough that it became the standard design > of > tube type broadcast transmitters starting in the late 50's. > > I used that circuit with the first high power rf final I ever built, > using a > 304-TL in the final, because I didn't have a large split stator tuning > capacitor on hand. > > Don K4KYV > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > > > > __ > AMRadio 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] Home brew AM Cathode modualtion
The "Rice" neutralization circuit works better with a higher Q grid tank and, if possible, some input swamping or grid load resistor. The biggest trouble with the circuit is that the loading of the grid tank is not constant over the full RF cycle as a result the "Q" and balance is shifted somewhat over the period of the RF cycle. Starting with a higher "Q" or C value is one way of minimizing this effect. The circuit does work because I used it as well and also with a 304TLs, back in the days of experimenting with the ultra modulation or balanced high level modulation circuits. I eventually went to standard "Push Pull". John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Donald Chester Sent: Sunday, October 03, 2004 12:45 PM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Home brew AM Cathode modualtion >The 450th is a big triode, so I don't think you can run it single ended pie >net output, you would need to do 2 250th tubes in push pull or something, >but the 450th would do the cathode modulator quite well. You could use a single-ended pi-network type output circuit, with a balanced grid tank coil. That is knows as "Rice" neutralisation. You don't get as perfect null as you can with a balanced plate tank cincuit or a pushpull arrangement, but it works well enough that it became the standard design of tube type broadcast transmitters starting in the late 50's. I used that circuit with the first high power rf final I ever built, using a 304-TL in the final, because I didn't have a large split stator tuning capacitor on hand. Don K4KYV __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] Home brew AM Cathode modualtion
The 450th is a big triode, so I dont think you can run it single ended pie net output, you would need to do 2 250th tubes in push pull or something, but the 450th would do the cathode modulator quite well. You could use a single-ended pi-network type output circuit, with a balanced grid tank coil. That is knows as "Rice" neutralisation. You don't get as perfect null as you can with a balanced plate tank cincuit or a pushpull arrangement, but it works well enough that it became the standard design of tube type broadcast transmitters starting in the late 50's. I used that circuit with the first high power rf final I ever built, using a 304-TL in the final, because I didn't have a large split stator tuning capacitor on hand. Don K4KYV
Re: [AMRadio] Home brew AM
How does that compare to the performance of say the 250TH final stage in a BC-610? It sounds like you are running at lower power. Also how many tubes do you use in the cathode modulator? On 2 Oct 2004 at 20:12, Patrick Jankowiak wrote: > Cathode mod works very well on a 250TH. We are getting 80-90 > watts carrier no problem at 2200V. For the details: > > http://www.montagar.com/~patj/cathmod01.htm > > > Patrick > __ > 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] Home brew AM
Cathode mod works very well on a 250TH. We are getting 80-90 watts carrier no problem at 2200V. For the details: http://www.montagar.com/~patj/cathmod01.htm Patrick
RE: [AMRadio] Home brew AM Cathode modualtion
My two cent worth for the new guys that might not understand: The technique that is used in the drawing of Jim's (JKO) showed a 6146 in the final. This circuit is simply a class A audio circuit that has been placed in series with the finals B+ and screen common circuit. In this case the grid leak bias resistor has been returned to the cathode so that the grid bias on the final stays constant with modulation (except for the small usual grid leak self modulation phenomenon that occurs on any high level modulated stage with grid leak bias) The circuit could be modified placing the modulators in series with the +1100 volt DC input and the results would be the same (see note "1"). The plate efficiency of the Class "C" final is as good as any, but the modulators will dissipate a lot of heat because of the class "A" operation with less that 25% efficiency. The overall efficiency is not good. The beauty of this circuit is no modulation XFMR with a trade off for modulator efficiency. It does require a separate filament source with good insulation for the class "C" final to prevent filament to cathode breakdown and make sure you get all the RF bypassed or filtered on the final's cathode. It also requires twice as much DC supply voltage. (NOTE 1) Placing the modulator tubes in the cathode return of the final, as shown, is a better construction technique that allows the modulator cathodes to be grounded or biased in a normal manor (close to ground potential, therefore allowing for normal RC coupling to the grids of the modulator tubes). If the circuit were modified, placing the modulator tube in the plate circuit, then the cathode of the modulators would be at a very high voltage. This would mean that the coupling to the grid of the modulator would need special consideration or XFMR coupling, defeating the one of the purposes of the circuit. Also, the filament source for the modulators would need to be connected to the cathode of the modulators and a special filament supply winding with good insulation would be needed to handle the high voltage that would be on the modulators. None the less, theory of operation to the final is the same. It is still high level modulation. The secondary of a modulation XFMR could be place where the series modulator tubes are, and the supply voltage dropped by the amount used by the series modulator tubes, and there would be no difference than if the modulation transformer were placed where you commonly see it in the plate circuit of the final. Good Luck, John, WA5BXO
RE: [AMRadio] Home brew AM
Thanks for the info Jim. I will add this to the Boatanchors Directory... There are several other AM "Cathode Mod" links there too http://www.af4k.com/Boatanchors_Directory/ On 1 Oct 2004 at 21:43, Jim candela wrote: > > Guys, > > I have accumulated a couple of circuits for series cathode modulation. > One is for a 6146 final, and the other for a 807 final, and both use a sweep > tube or two for the cathode modulator. > > Using this technique for QRO AM at 375 watts carrier output will be > pretty > inefficient since the modulator tube will likely be class A. It could be > class D or E switch mode with a good Low pass filter. I believe that some > early KA1SI PDM rigs used some big tubes this way. As for the filament > transformer, a high standoff is really no big deal so long as you wind it > yourself and insulate accordingly. Heck I once made a 208 VAC to 60 VCT at > 200 amps where I needed 120 KV insulation primary to secondary. Layers of > Mylar sheet (like shingles) and transformer oil did the trick. Could also > maybe use a ferrite horizontal fly back transformer (custom wound) for the > filament. Why use 60 hertz? Could be 50 Khz so long as the filament is at > the right temperature. > > Here is a link to two different cathode modulated AM rigs: > > http://pages.prodigy.net/jcandela/Modulator/ > > > Regards, > Jim > WD5JKO > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Brett gazdzinski > Sent: Friday, October 01, 2004 7:42 AM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] Home brew AM > > > Clay, > Sounds like a cool idea, and I always thought it should work well > since there is no mod iron. > > I would go for a lower output using lower voltage though, with different > tubes. > 4500 volts is a lot to expect a filament transformer to handle, and if it > arcs over, it could be into the 110 ac side! > > The 450th is a big triode, so I dont think you can run it single ended > pie net output, you would need to do 2 250th tubes in push pull or > something, > but the 450th would do the cathode modulator quite well. > > It would be interesting to look at what available tubes would work > with this type of circuit. > There are some nice modern tubes to play with, 3cx800's and other > big triodes, or, if it could work, tetrodes. > Not sure how cathode modulating a tetrode would work out. > > If you could cathode modulate a pie net output tetrode, that would open > up a lot of possibilities. > Maybe find one that runs a lower voltage but is good for some power... > > Brett > N2DTS > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Clay W7CE > Sent: Thursday, September 30, 2004 12:52 PM > To: Discussion of AM Radio > Subject: Re: [AMRadio] Home brew AM > > > One option that isn't discussed often because it is considered inefficient > at high power is series cathode modulation. This is accomplished by putting > the modulator tube between the RF amplifier tube's cathode and ground. The > only apparent inefficiency is that you run the RF amp at one fourth of it's > Class C CW power rating. I'm currently considering building such a rig > using a 450TH for the RF amp and another 450TH for the modulator. At 4500V, > the 450TH is good for about 1500W out on CW, and with the modulator tube > added will drop to about 375W of carrier. On modulation peaks it will hit > the tubes CW power level of 1500W. The tube will be doing fairly light duty > at this power level since it can handle 1500W CCS output at 4500V, and > should last a very long time as a result. Based on the price and weight of > 450TH's vs. large mod transformers, I think it's a good trade off. In > addition, the fidelity and audio response will be limited primarily by the > audio driver, not the mod transformer. On the negative side, I have to run > the plates at 4500V vs. about 2500V for plate modulation. The filament > transformer for the RF amp will also need to be hi-pot tested to 4500-5000V > (anyone willing to part with a pair of 7.5V, 12A filament transformers that > will work for this?). > > Any thoughts and advice on this approach will be appreciated. > > Clay W7CE > > > - Original Message - > From: "Brett gazdzinski" <[EMAIL PROTECTED]> > To: "'Discussion of AM Radio'" > Sent: Thursday, September 30, 2004 9:03 AM > Subject: RE: [AMRadio] Home brew AM > > > That would be hard, but not impossible. > You would need to read up on mod transformer construction, > find something to use as a core, and wind lo
RE: [AMRadio] Home brew AM
Guys, I have accumulated a couple of circuits for series cathode modulation. One is for a 6146 final, and the other for a 807 final, and both use a sweep tube or two for the cathode modulator. Using this technique for QRO AM at 375 watts carrier output will be pretty inefficient since the modulator tube will likely be class A. It could be class D or E switch mode with a good Low pass filter. I believe that some early KA1SI PDM rigs used some big tubes this way. As for the filament transformer, a high standoff is really no big deal so long as you wind it yourself and insulate accordingly. Heck I once made a 208 VAC to 60 VCT at 200 amps where I needed 120 KV insulation primary to secondary. Layers of Mylar sheet (like shingles) and transformer oil did the trick. Could also maybe use a ferrite horizontal fly back transformer (custom wound) for the filament. Why use 60 hertz? Could be 50 Khz so long as the filament is at the right temperature. Here is a link to two different cathode modulated AM rigs: http://pages.prodigy.net/jcandela/Modulator/ Regards, Jim WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Brett gazdzinski Sent: Friday, October 01, 2004 7:42 AM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] Home brew AM Clay, Sounds like a cool idea, and I always thought it should work well since there is no mod iron. I would go for a lower output using lower voltage though, with different tubes. 4500 volts is a lot to expect a filament transformer to handle, and if it arcs over, it could be into the 110 ac side! The 450th is a big triode, so I dont think you can run it single ended pie net output, you would need to do 2 250th tubes in push pull or something, but the 450th would do the cathode modulator quite well. It would be interesting to look at what available tubes would work with this type of circuit. There are some nice modern tubes to play with, 3cx800's and other big triodes, or, if it could work, tetrodes. Not sure how cathode modulating a tetrode would work out. If you could cathode modulate a pie net output tetrode, that would open up a lot of possibilities. Maybe find one that runs a lower voltage but is good for some power... Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Clay W7CE Sent: Thursday, September 30, 2004 12:52 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Home brew AM One option that isn't discussed often because it is considered inefficient at high power is series cathode modulation. This is accomplished by putting the modulator tube between the RF amplifier tube's cathode and ground. The only apparent inefficiency is that you run the RF amp at one fourth of it's Class C CW power rating. I'm currently considering building such a rig using a 450TH for the RF amp and another 450TH for the modulator. At 4500V, the 450TH is good for about 1500W out on CW, and with the modulator tube added will drop to about 375W of carrier. On modulation peaks it will hit the tubes CW power level of 1500W. The tube will be doing fairly light duty at this power level since it can handle 1500W CCS output at 4500V, and should last a very long time as a result. Based on the price and weight of 450TH's vs. large mod transformers, I think it's a good trade off. In addition, the fidelity and audio response will be limited primarily by the audio driver, not the mod transformer. On the negative side, I have to run the plates at 4500V vs. about 2500V for plate modulation. The filament transformer for the RF amp will also need to be hi-pot tested to 4500-5000V (anyone willing to part with a pair of 7.5V, 12A filament transformers that will work for this?). Any thoughts and advice on this approach will be appreciated. Clay W7CE - Original Message - From: "Brett gazdzinski" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Thursday, September 30, 2004 9:03 AM Subject: RE: [AMRadio] Home brew AM That would be hard, but not impossible. You would need to read up on mod transformer construction, find something to use as a core, and wind loads of wire on it, keeping in mind the very high voltages that it would have to withstand. You can buy mod transformers, peter dahl makes new ones, ebay, etc. Old surplus is best, old military rigs, broadcast rigs, old ham rigs... I am using mod transformers that were built by RCA in the 1940's for some sort of ship board radio for the Dutch navy I have been told. Without any mod iron, you would have to go to some sort of screen modulation with large tubes. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of GGLL Sent: Wednesday, September 29, 2004 7:55 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Home brew AM Hello people, I agree with the nice look and sme
RE: [AMRadio] Home brew AM
Clay, Sounds like a cool idea, and I always thought it should work well since there is no mod iron. I would go for a lower output using lower voltage though, with different tubes. 4500 volts is a lot to expect a filament transformer to handle, and if it arcs over, it could be into the 110 ac side! The 450th is a big triode, so I dont think you can run it single ended pie net output, you would need to do 2 250th tubes in push pull or something, but the 450th would do the cathode modulator quite well. It would be interesting to look at what available tubes would work with this type of circuit. There are some nice modern tubes to play with, 3cx800's and other big triodes, or, if it could work, tetrodes. Not sure how cathode modulating a tetrode would work out. If you could cathode modulate a pie net output tetrode, that would open up a lot of possibilities. Maybe find one that runs a lower voltage but is good for some power... Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Clay W7CE Sent: Thursday, September 30, 2004 12:52 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Home brew AM One option that isn't discussed often because it is considered inefficient at high power is series cathode modulation. This is accomplished by putting the modulator tube between the RF amplifier tube's cathode and ground. The only apparent inefficiency is that you run the RF amp at one fourth of it's Class C CW power rating. I'm currently considering building such a rig using a 450TH for the RF amp and another 450TH for the modulator. At 4500V, the 450TH is good for about 1500W out on CW, and with the modulator tube added will drop to about 375W of carrier. On modulation peaks it will hit the tubes CW power level of 1500W. The tube will be doing fairly light duty at this power level since it can handle 1500W CCS output at 4500V, and should last a very long time as a result. Based on the price and weight of 450TH's vs. large mod transformers, I think it's a good trade off. In addition, the fidelity and audio response will be limited primarily by the audio driver, not the mod transformer. On the negative side, I have to run the plates at 4500V vs. about 2500V for plate modulation. The filament transformer for the RF amp will also need to be hi-pot tested to 4500-5000V (anyone willing to part with a pair of 7.5V, 12A filament transformers that will work for this?). Any thoughts and advice on this approach will be appreciated. Clay W7CE - Original Message - From: "Brett gazdzinski" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Thursday, September 30, 2004 9:03 AM Subject: RE: [AMRadio] Home brew AM That would be hard, but not impossible. You would need to read up on mod transformer construction, find something to use as a core, and wind loads of wire on it, keeping in mind the very high voltages that it would have to withstand. You can buy mod transformers, peter dahl makes new ones, ebay, etc. Old surplus is best, old military rigs, broadcast rigs, old ham rigs... I am using mod transformers that were built by RCA in the 1940's for some sort of ship board radio for the Dutch navy I have been told. Without any mod iron, you would have to go to some sort of screen modulation with large tubes. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of GGLL Sent: Wednesday, September 29, 2004 7:55 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Home brew AM Hello people, I agree with the nice look and smell of "glass" AM. Few years ago, I made my CW/AM transmitter, with an 807 plate/screen modulated, 50 watts CW, 40 watts AM output. Started with a triode/pentode oscillator/doubler VFO, then converted to solid state oscillator/buffer, followed by a tube driver (6BQ5) and finally the 807 to a pi tank output. Making my own plate modulated transmitter (200..300 watts out) is a buzzing idea in my mind since a couple of months. But here the most difficult item to get is the modulation transformer, does someone know a method to build it by myself?. Many thanks in advance Best regards Guillermo - LU8EYW. Brett gazdzinski escribió: > Steve, > What do you need, everything? > > Here's a partial list of what you need: > > 3 Chassis 17x3x14, > 3 panels 19x10.25?, > 3 sets of side supports, > Power transformer to give 1500 volts at 500 plus ma, > Choke at 500 plus ma, two is better, swinging for the modulator, > Rectifiers (I like the k2aw? bricks), > Modulation transformer, > Bleeder resistors, > Big relay and time delay relay for step start if you go that route, > 4 Tube sockets, > Filament transformers, > Killowatt plug in tank coils and its socket and swinging link, > Push pull grid coils for the bands wanted, > Push pull grid tuning c
Re: [AMRadio] Home brew AM
A few miles east of Johnstown, PA Dave, W3ST Publisher of the Collins Journal Secretary to the Collins Radio Association www.collinsra.com Nets: 3805 Khz, Monday/Wednesdays 8 PM EDST 14250 Khz Saturday, 12 Noon EDST - Original Message - From: "Neal Newman" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, September 30, 2004 4:03 PM Subject: Re: [AMRadio] Home brew AM > David where are you located?? > > > David Knepper wrote: > > >Fall Hamfest at the Collins Radio Center, throughout the month of 2004 > > > >Liquidation of Heavy iron, test equipment, large variables, 1KW coils with > >butterfly capacitors, large transmitting tubes, too many items to list. > > > >No shipping. > > > >No reasonable offer refused. If you plan on stopping by to see the museum > >and look over the cache, let me know when you will be arriving. > > > >Thank you > > > >Dave, W3ST > >Publisher of the Collins Journal > >Secretary to the Collins Radio Association > >www.collinsra.com > >Nets: 3805 Khz, Monday/Wednesdays 8 PM EDST > > 14250 Khz Saturday, 12 Noon EDST > > > > > >__ > >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] Home brew AM
David where are you located?? David Knepper wrote: Fall Hamfest at the Collins Radio Center, throughout the month of 2004 Liquidation of Heavy iron, test equipment, large variables, 1KW coils with butterfly capacitors, large transmitting tubes, too many items to list. No shipping. No reasonable offer refused. If you plan on stopping by to see the museum and look over the cache, let me know when you will be arriving. Thank you Dave, W3ST Publisher of the Collins Journal Secretary to the Collins Radio Association www.collinsra.com Nets: 3805 Khz, Monday/Wednesdays 8 PM EDST 14250 Khz Saturday, 12 Noon EDST __ 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] Home brew AM
Fall Hamfest at the Collins Radio Center, throughout the month of 2004 Liquidation of Heavy iron, test equipment, large variables, 1KW coils with butterfly capacitors, large transmitting tubes, too many items to list. No shipping. No reasonable offer refused. If you plan on stopping by to see the museum and look over the cache, let me know when you will be arriving. Thank you Dave, W3ST Publisher of the Collins Journal Secretary to the Collins Radio Association www.collinsra.com Nets: 3805 Khz, Monday/Wednesdays 8 PM EDST 14250 Khz Saturday, 12 Noon EDST
Re: [AMRadio] Home brew AM
One option that isn't discussed often because it is considered inefficient at high power is series cathode modulation. This is accomplished by putting the modulator tube between the RF amplifier tube's cathode and ground. The only apparent inefficiency is that you run the RF amp at one fourth of it's Class C CW power rating. I'm currently considering building such a rig using a 450TH for the RF amp and another 450TH for the modulator. At 4500V, the 450TH is good for about 1500W out on CW, and with the modulator tube added will drop to about 375W of carrier. On modulation peaks it will hit the tubes CW power level of 1500W. The tube will be doing fairly light duty at this power level since it can handle 1500W CCS output at 4500V, and should last a very long time as a result. Based on the price and weight of 450TH's vs. large mod transformers, I think it's a good trade off. In addition, the fidelity and audio response will be limited primarily by the audio driver, not the mod transformer. On the negative side, I have to run the plates at 4500V vs. about 2500V for plate modulation. The filament transformer for the RF amp will also need to be hi-pot tested to 4500-5000V (anyone willing to part with a pair of 7.5V, 12A filament transformers that will work for this?). Any thoughts and advice on this approach will be appreciated. Clay W7CE - Original Message - From: "Brett gazdzinski" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Thursday, September 30, 2004 9:03 AM Subject: RE: [AMRadio] Home brew AM That would be hard, but not impossible. You would need to read up on mod transformer construction, find something to use as a core, and wind loads of wire on it, keeping in mind the very high voltages that it would have to withstand. You can buy mod transformers, peter dahl makes new ones, ebay, etc. Old surplus is best, old military rigs, broadcast rigs, old ham rigs... I am using mod transformers that were built by RCA in the 1940's for some sort of ship board radio for the Dutch navy I have been told. Without any mod iron, you would have to go to some sort of screen modulation with large tubes. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of GGLL Sent: Wednesday, September 29, 2004 7:55 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Home brew AM Hello people, I agree with the nice look and smell of "glass" AM. Few years ago, I made my CW/AM transmitter, with an 807 plate/screen modulated, 50 watts CW, 40 watts AM output. Started with a triode/pentode oscillator/doubler VFO, then converted to solid state oscillator/buffer, followed by a tube driver (6BQ5) and finally the 807 to a pi tank output. Making my own plate modulated transmitter (200..300 watts out) is a buzzing idea in my mind since a couple of months. But here the most difficult item to get is the modulation transformer, does someone know a method to build it by myself?. Many thanks in advance Best regards Guillermo - LU8EYW. Brett gazdzinski escribió: > Steve, > What do you need, everything? > > Here's a partial list of what you need: > > 3 Chassis 17x3x14, > 3 panels 19x10.25?, > 3 sets of side supports, > Power transformer to give 1500 volts at 500 plus ma, > Choke at 500 plus ma, two is better, swinging for the modulator, > Rectifiers (I like the k2aw? bricks), > Modulation transformer, > Bleeder resistors, > Big relay and time delay relay for step start if you go that route, > 4 Tube sockets, > Filament transformers, > Killowatt plug in tank coils and its socket and swinging link, > Push pull grid coils for the bands wanted, > Push pull grid tuning cap (150 to 200 pf per section, low voltage) > Modulator grid drive transformer 8 to 10,000 ohms roughly at 20 or more > watts, > 2 Neutralizing caps, > 4 811a tubes, > Grid leak resistor (big wire wound pot works well), > Insulated shaft couplings, > Plate tuning cap, dual 100 pf 5000 volts or better, > Meters for grid current, mod current, plate voltage, plate current, > > A large pile of wire, high voltage wire, screws, nuts, knobs, connector > strips, line cord, switches, lights, panel bushings,fuse and holder or > breaker, > spacers, ceramic standoffs, rf connectors, etc. > > I could give you some stuff, and sell you some stuff most likely, and > MIGHT be able to get you a mod transformer. > > Brett > N2DTS > > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > Sent: Wednesday, September 29, 2004 9:52 AM > To: amradio@mailman.qth.net > Subject: [AMRadio] Home brew AM > > > Thanks for the replies. > > The 812/811 combo was sorta what I had in mind. > > Getting the components sho
RE: [AMRadio] Home brew AM
That would be hard, but not impossible. You would need to read up on mod transformer construction, find something to use as a core, and wind loads of wire on it, keeping in mind the very high voltages that it would have to withstand. You can buy mod transformers, peter dahl makes new ones, ebay, etc. Old surplus is best, old military rigs, broadcast rigs, old ham rigs... I am using mod transformers that were built by RCA in the 1940's for some sort of ship board radio for the Dutch navy I have been told. Without any mod iron, you would have to go to some sort of screen modulation with large tubes. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of GGLL Sent: Wednesday, September 29, 2004 7:55 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Home brew AM Hello people, I agree with the nice look and smell of "glass" AM. Few years ago, I made my CW/AM transmitter, with an 807 plate/screen modulated, 50 watts CW, 40 watts AM output. Started with a triode/pentode oscillator/doubler VFO, then converted to solid state oscillator/buffer, followed by a tube driver (6BQ5) and finally the 807 to a pi tank output. Making my own plate modulated transmitter (200..300 watts out) is a buzzing idea in my mind since a couple of months. But here the most difficult item to get is the modulation transformer, does someone know a method to build it by myself?. Many thanks in advance Best regards Guillermo - LU8EYW. Brett gazdzinski escribió: > Steve, > What do you need, everything? > > Here's a partial list of what you need: > > 3 Chassis 17x3x14, > 3 panels 19x10.25?, > 3 sets of side supports, > Power transformer to give 1500 volts at 500 plus ma, > Choke at 500 plus ma, two is better, swinging for the modulator, > Rectifiers (I like the k2aw? bricks), > Modulation transformer, > Bleeder resistors, > Big relay and time delay relay for step start if you go that route, > 4 Tube sockets, > Filament transformers, > Killowatt plug in tank coils and its socket and swinging link, > Push pull grid coils for the bands wanted, > Push pull grid tuning cap (150 to 200 pf per section, low voltage) > Modulator grid drive transformer 8 to 10,000 ohms roughly at 20 or more > watts, > 2 Neutralizing caps, > 4 811a tubes, > Grid leak resistor (big wire wound pot works well), > Insulated shaft couplings, > Plate tuning cap, dual 100 pf 5000 volts or better, > Meters for grid current, mod current, plate voltage, plate current, > > A large pile of wire, high voltage wire, screws, nuts, knobs, connector > strips, line cord, switches, lights, panel bushings,fuse and holder or > breaker, > spacers, ceramic standoffs, rf connectors, etc. > > I could give you some stuff, and sell you some stuff most likely, and > MIGHT be able to get you a mod transformer. > > Brett > N2DTS > > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > Sent: Wednesday, September 29, 2004 9:52 AM > To: amradio@mailman.qth.net > Subject: [AMRadio] Home brew AM > > > Thanks for the replies. > > The 812/811 combo was sorta what I had in mind. > > Getting the components shouldn't be too hard if I keep searching. > > Let me start here...anyone have any suitable parts? > > About the E class...read a few things about it...sounds most > interesting...but MOSFETS don't have the fragrance of warm vacuum tubes on a > chilly winters evening nor the soft orange glow cast through the rig > perforations onto the shack walls to keep one company...nor the humming > vibrations of pumped RF being piped to the outside antenna. > > 73 > Steve WA2TAK __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] Home brew AM
Hello people, I agree with the nice look and smell of "glass" AM. Few years ago, I made my CW/AM transmitter, with an 807 plate/screen modulated, 50 watts CW, 40 watts AM output. Started with a triode/pentode oscillator/doubler VFO, then converted to solid state oscillator/buffer, followed by a tube driver (6BQ5) and finally the 807 to a pi tank output. Making my own plate modulated transmitter (200..300 watts out) is a buzzing idea in my mind since a couple of months. But here the most difficult item to get is the modulation transformer, does someone know a method to build it by myself?. Many thanks in advance Best regards Guillermo - LU8EYW. Brett gazdzinski escribió: Steve, What do you need, everything? Here's a partial list of what you need: 3 Chassis 17x3x14, 3 panels 19x10.25?, 3 sets of side supports, Power transformer to give 1500 volts at 500 plus ma, Choke at 500 plus ma, two is better, swinging for the modulator, Rectifiers (I like the k2aw? bricks), Modulation transformer, Bleeder resistors, Big relay and time delay relay for step start if you go that route, 4 Tube sockets, Filament transformers, Killowatt plug in tank coils and its socket and swinging link, Push pull grid coils for the bands wanted, Push pull grid tuning cap (150 to 200 pf per section, low voltage) Modulator grid drive transformer 8 to 10,000 ohms roughly at 20 or more watts, 2 Neutralizing caps, 4 811a tubes, Grid leak resistor (big wire wound pot works well), Insulated shaft couplings, Plate tuning cap, dual 100 pf 5000 volts or better, Meters for grid current, mod current, plate voltage, plate current, A large pile of wire, high voltage wire, screws, nuts, knobs, connector strips, line cord, switches, lights, panel bushings,fuse and holder or breaker, spacers, ceramic standoffs, rf connectors, etc. I could give you some stuff, and sell you some stuff most likely, and MIGHT be able to get you a mod transformer. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, September 29, 2004 9:52 AM To: amradio@mailman.qth.net Subject: [AMRadio] Home brew AM Thanks for the replies. The 812/811 combo was sorta what I had in mind. Getting the components shouldn't be too hard if I keep searching. Let me start here...anyone have any suitable parts? About the E class...read a few things about it...sounds most interesting...but MOSFETS don't have the fragrance of warm vacuum tubes on a chilly winters evening nor the soft orange glow cast through the rig perforations onto the shack walls to keep one company...nor the humming vibrations of pumped RF being piped to the outside antenna. 73 Steve WA2TAK __ 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] Home brew AM
Steve, What do you need, everything? Here's a partial list of what you need: 3 Chassis 17x3x14, 3 panels 19x10.25?, 3 sets of side supports, Power transformer to give 1500 volts at 500 plus ma, Choke at 500 plus ma, two is better, swinging for the modulator, Rectifiers (I like the k2aw? bricks), Modulation transformer, Bleeder resistors, Big relay and time delay relay for step start if you go that route, 4 Tube sockets, Filament transformers, Killowatt plug in tank coils and its socket and swinging link, Push pull grid coils for the bands wanted, Push pull grid tuning cap (150 to 200 pf per section, low voltage) Modulator grid drive transformer 8 to 10,000 ohms roughly at 20 or more watts, 2 Neutralizing caps, 4 811a tubes, Grid leak resistor (big wire wound pot works well), Insulated shaft couplings, Plate tuning cap, dual 100 pf 5000 volts or better, Meters for grid current, mod current, plate voltage, plate current, A large pile of wire, high voltage wire, screws, nuts, knobs, connector strips, line cord, switches, lights, panel bushings,fuse and holder or breaker, spacers, ceramic standoffs, rf connectors, etc. I could give you some stuff, and sell you some stuff most likely, and MIGHT be able to get you a mod transformer. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, September 29, 2004 9:52 AM To: amradio@mailman.qth.net Subject: [AMRadio] Home brew AM Thanks for the replies. The 812/811 combo was sorta what I had in mind. Getting the components shouldn't be too hard if I keep searching. Let me start here...anyone have any suitable parts? About the E class...read a few things about it...sounds most interesting...but MOSFETS don't have the fragrance of warm vacuum tubes on a chilly winters evening nor the soft orange glow cast through the rig perforations onto the shack walls to keep one company...nor the humming vibrations of pumped RF being piped to the outside antenna. 73 Steve WA2TAK __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
