Re: [AMRadio] AM Transmitter Advice?? (meter time constant)
From: Bob Bruhns [EMAIL PROTECTED] Bacon, not trying to be contrite, but where in the old rules did the .25 second time constant appear? I have a copy of the old rules and don't see it. It says only that have the means. Hi Jim... Hmm, it came from my sometimes flakey memory... I'm pretty sure there was a 0.25 second spec for the metering somewhere... maybe it was simply assumed that the meter time constant would be about 0.25 seconds. From ARRL's Single Sideband for the Radio Amateur, p. 14, 1958 edition: S.S.B. POWER LIMIT ...We quote from a Commission letter addressed to ARRL: The following . . . may be considered as a presently acceptable method for determining the d.c. plate power input to the final r.f. stage of a single-sideband amateur transmitter: The maximum d.c. plate power input to the radio frequency tube or tubes supplying power to the antenna system of a single-sideband suppressed-carrier transmitter, as indicated by the usual plate voltmeter and plate milliammeter, shall be considered as the input power insofar as Sections 12.131 and 12.136(d) of the Commission's rules are concerned, provided the plate meters utilized have a time constant not in excess of approximately 0.25 second, and the linearity of the transmitter has been adjusted to prevent the generation of excessive sidebands. The input power shall not exceed one kilowatt on peaks as indicated by the plate meter readings. Don k4kyv
Re: [AMRadio] AM Transmitter Advice?? (meter time constant)
Hi Don: Damn topic! This started me wondering about measuring PEP and Carrier Power today. So I went to the FCC website to look for the standards that apply. Well I finally found it. Here is a link to Chapter 1-FCC, Subpart J, Section 2.1046, if anyone is interested in reading it. I hope the link works. http://a257.g.akamaitech.net/7/257/2422/09nov20051500/edocket.access.gpo.gov/cfr_2005/octqtr/47cfr2.1046.htm This was originally 39 FR 5919, 2/15/74Redesign and amended at 63 FR 36599, 7/7/98 Good reading if one wishes to be compliant. 73 Jim W5JO - Original Message - From: Donald Chester [EMAIL PROTECTED] To: amradio@mailman.qth.net Sent: Monday, February 20, 2006 11:00 AM Subject: Re: [AMRadio] AM Transmitter Advice?? (meter time constant) From: Bob Bruhns [EMAIL PROTECTED] Bacon, not trying to be contrite, but where in the old rules did the .25 second time constant appear? I have a copy of the old rules and don't see it. It says only that have the means. Hi Jim... Hmm, it came from my sometimes flakey memory... I'm pretty sure there was a 0.25 second spec for the metering somewhere... maybe it was simply assumed that the meter time constant would be about 0.25 seconds. From ARRL's Single Sideband for the Radio Amateur, p. 14, 1958 edition: S.S.B. POWER LIMIT ...We quote from a Commission letter addressed to ARRL: The following . . . may be considered as a presently acceptable method for determining the d.c. plate power input to the final r.f. stage of a single-sideband amateur transmitter: The maximum d.c. plate power input to the radio frequency tube or tubes supplying power to the antenna system of a single-sideband suppressed-carrier transmitter, as indicated by the usual plate voltmeter and plate milliammeter, shall be considered as the input power insofar as Sections 12.131 and 12.136(d) of the Commission's rules are concerned, provided the plate meters utilized have a time constant not in excess of approximately 0.25 second, and the linearity of the transmitter has been adjusted to prevent the generation of excessive sidebands. The input power shall not exceed one kilowatt on peaks as indicated by the plate meter readings. Don k4kyv
Re: [AMRadio] AM Transmitter Advice?? (meter time constant)
From: Jim Wilhite [EMAIL PROTECTED] This started me wondering about measuring PEP and Carrier Power today. So I went to the FCC website to look for the standards that apply. Well I finally found it. Here is a link to Chapter 1-FCC, Subpart J, Section 2.1046, if anyone is interested in reading it. I hope the link works. http://a257.g.akamaitech.net/7/257/2422/09nov20051500/edocket.access.gpo.gov/cfr_2005/octqtr/47cfr2.1046.htm This was originally 39 FR 5919, 2/15/74Redesign and amended at 63 FR 36599, 7/7/98 Good reading if one wishes to be compliant. Brings up a couple of interesting points: (1) Looks like they state two separate power standards: carrier power for steady output emissions like FM, AM, CW, etc., and p.e.p. for modes with fluctuating output, like SSB, ISB and controlled carrier. If the AMATEUR regulations had been written that way, there would have been no AM power reduction. The power output rules ARE written in that fashion in Canada. (2) ...The electrical characteristics of the radio frequency load attached to the output terminals when this test is made shall be stated. Fat chance that more than about 1% of amateur installations could meet that criteria. It requires working into a known, nonreactive, purely resistive load. How many ham antennas present a perfectly flat swr and 50-ohm nonreactive load at the transmitter end of the feedline? This measurement would require a calibrated rf impedance bridge, and knowledge of how to use it. How many appliance operators of today would qualify? Don K4KYV ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
Re: [AMRadio] AM Transmitter Advice?? (meter time constant)
Interesting thought isn't it Don? 97.303 simply states that (a) An amateur station must use the minimum transmitter power necessary to carry out the desired communications. (b) No station may transmit with a transmitter power exceeding 1.5 kW PEP. So my question is, when the FCC rolls into my yard to check my power output, how are they going to proceed? If this is the answer, then your conversations are correct, and/or they aren't ever going to check! Interesting question isn't it? So am I supposed to rely on those expensive PEP meters that are sold to the amateur population, or simply put an RF ammeter in the output line and do the calculations? Seems to me the RF ammeter might be the best investment, and much less expensive. But that would require us to know a little Algebra, would it? 73 Jim W5JO - Original Message - From: Donald Chester [EMAIL PROTECTED] To: amradio@mailman.qth.net Sent: Monday, February 20, 2006 5:51 PM Subject: Re: [AMRadio] AM Transmitter Advice?? (meter time constant) From: Jim Wilhite [EMAIL PROTECTED] This started me wondering about measuring PEP and Carrier Power today. So I went to the FCC website to look for the standards that apply. Well I finally found it. Here is a link to Chapter 1-FCC, Subpart J, Section 2.1046, if anyone is interested in reading it. I hope the link works. http://a257.g.akamaitech.net/7/257/2422/09nov20051500/edocket.access.gpo.gov/cfr_2005/octqtr/47cfr2.1046.htm This was originally 39 FR 5919, 2/15/74Redesign and amended at 63 FR 36599, 7/7/98 Good reading if one wishes to be compliant. Brings up a couple of interesting points: (1) Looks like they state two separate power standards: carrier power for steady output emissions like FM, AM, CW, etc., and p.e.p. for modes with fluctuating output, like SSB, ISB and controlled carrier. If the AMATEUR regulations had been written that way, there would have been no AM power reduction. The power output rules ARE written in that fashion in Canada. (2) ...The electrical characteristics of the radio frequency load attached to the output terminals when this test is made shall be stated. Fat chance that more than about 1% of amateur installations could meet that criteria. It requires working into a known, nonreactive, purely resistive load. How many ham antennas present a perfectly flat swr and 50-ohm nonreactive load at the transmitter end of the feedline? This measurement would require a calibrated rf impedance bridge, and knowledge of how to use it. How many appliance operators of today would qualify? Don K4KYV
Re: [AMRadio] AM Transmitter Advice??
John E. Coleman (ARS WA5BXO) wrote: Don, I have heard rumors of a citation or two but only in extreme cases such as 10 or 20 KW PEP and I don't know if the rumors are true. As I understand it the trick, that the FCC was to prevent, and someone was trying to get away with, was to run a 304TL with about 100 Volts on the plate in a GG configuration. Forward bias it to a high plate current like 1 Amp, so that it acts like a switch that is on. Then drive it with 5 KW PEP. It may have been some other some scenario as this but I think you get the picture. An Now, For Something Completely Different. Then there was the trick that a gentleman up in 3 land, I think, was going to run the high level double sideband reduced carrier generator type rig but he was not reducing the carrier just increasing the SBs via an extra upside down tube, as it was commonly called. The sideband power would continue to go up without distortion (if copied on a proper synchronized product detector) after the first tube was over modulated in the negative direction. The voltage and power would be diverted to the upside down tube where sideband power would continue. There was trouble with the specific rule interpretation at the time in the FCC. Of course any of us today, would be able to see that the upside down tube's audio plate current and audio voltage must also be counted as part of the input power. But the FCC was having trouble deciding, at least as I understand it. At any rate, I think they got him for being outside the 40 meter band limits. You may remember more of the specifics on this Don. John, WA5BXO Fred, I believe. W3PHL.
Re: [AMRadio] AM Transmitter Advice??
I like my 100 watt linear with four 6AG7s. Healthfully yours, DON W4BWS - Original Message - From: Brian Carling [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Friday, February 17, 2006 6:41 AM Subject: RE: [AMRadio] AM Transmitter Advice?? I bet you a BC610 will out-peg a DX100 any day! Don't care what the numbers say... Grin! That 12AX7 linear amplifier sounds like more of a FUN project than a useful station accessory! Just WAIT until the experts start telling you it can't be done, you will only get 30% efficiency and all that jazz! LOL. 73 de AF4K, Bry On 17 Feb 2006 at 4:29, Jim Candela wrote: 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??
Hello Don! Hey - mount those 6AG7s upside down in cooling oil and you can run 500 watts to 'em. I wouldn't try it but I am sure SOMEONE has, LOL! I am getting healthier! 73 de AF4K, Bry On 18 Feb 2006 at 13:06, Rev. Don Sanders wrote: I like my 100 watt linear with four 6AG7s. Healthfully yours, DON W4BWS
Re: [AMRadio] AM Transmitter Advice??
From: Brian Carling [EMAIL PROTECTED] Hey - mount those 6AG7s upside down in cooling oil and you can run 500 watts to 'em. I wouldn't try it but I am sure SOMEONE has, LOL! My very first plate-modulated AM rig back in 1959 used a single 6AQ5 to drive a pair of 807's as class-B triodes with screen and control grids tied together with 20k resistors, and negative feedback round the 6AQ5. It would work for a few minutes, and then distortion would start to creep up. I finally figured out that the 6AQ5 was overheating and the distortion was due to thermal runaway. I turned the driver stage, which was haywired on a separate little chassis, upside down and let the 6AQ5 rest in a jar of water. That kept it just cool enough to keep away the distortion. But I would, on the average, overturn the jar of water at least once every time I tried to use that lashup. Don K4KYV ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
Re: [AMRadio] AM Transmitter Advice??
Donald Chester wrote: From: Brian Carling [EMAIL PROTECTED] Hey - mount those 6AG7s upside down in cooling oil and you can run 500 watts to 'em. I wouldn't try it but I am sure SOMEONE has, LOL! My very first plate-modulated AM rig back in 1959 used a single 6AQ5 to drive a pair of 807's as class-B triodes with screen and control grids tied together with 20k resistors, and negative feedback round the 6AQ5. It would work for a few minutes, and then distortion would start to creep up. I finally figured out that the 6AQ5 was overheating and the distortion was due to thermal runaway. I turned the driver stage, which was haywired on a separate little chassis, upside down and let the 6AQ5 rest in a jar of water. That kept it just cool enough to keep away the distortion. But I would, on the average, overturn the jar of water at least once every time I tried to use that lashup. Don K4KYV John/BXO can confirm this story; Gene White/WA5ATH(sk) had a plate modulated rig out in his garage, and a modulation transformer that made the awfulest racket of talk-back, when modulating the rig. The rig worked well, except for that talk-back. Someone (probably Otis/SWK) said maybe opearte with the transformer in a container of oil. So, Gene did. But (heh) he kept the oil in a styrofoam ice-chest.. The running, on-air, joke was ...what's the oil-pressure on your modulator, Gene? Mind you, this was also in the days when 'parts was parts' and who -cared- what something looked like, as long as it worked! Therefore, several parts were scrapped from rigs that server a different purpose in their life, and afterwards, such things as meters that indicated manifold pressure were used as current meters, etc... You know how home-brewers are. Ah, radio was a lot more fun, back then :-) -- 73 = Best Regards, -Geoff/W5OMR
RE: [AMRadio] AM Transmitter Advice??
My understanding was. Under the old rules stage or stages, that provide output to the antenna, total power should not exceed 1000 watts DC input. This includes the sum of the driver and final in the case of GG output circuit. I think that rule was tested. I recall that was the rule. But it seems to me it was much ado about nothing. At most, the feedthrough power would be 10% of the total output power. How much signal strength gain could you get from increasing your power 10%? Of course, back in those days the FCC was very nitpicky about the ham rules, as they still are with broadcast stations. But they have shifted to the opposite approach with ham radio. Riley's efforts have rooted out the rottenest of the apples, but I suspect ham radio enforcement is still pretty low on the FCC's priority list, as long as the violations don't cause interference to other radio services. Since they changed the power rule, I have never heard of a SINGLE case of a ham receiving a citation for running too much p.e.p. Don K4KYV ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
RE: [AMRadio] AM Transmitter Advice??
Don, I have heard rumors of a citation or two but only in extreme cases such as 10 or 20 KW PEP and I don't know if the rumors are true. As I understand it the trick, that the FCC was to prevent, and someone was trying to get away with, was to run a 304TL with about 100 Volts on the plate in a GG configuration. Forward bias it to a high plate current like 1 Amp, so that it acts like a switch that is on. Then drive it with 5 KW PEP. It may have been some other some scenario as this but I think you get the picture. An Now, For Something Completely Different. Then there was the trick that a gentleman up in 3 land, I think, was going to run the high level double sideband reduced carrier generator type rig but he was not reducing the carrier just increasing the SBs via an extra upside down tube, as it was commonly called. The sideband power would continue to go up without distortion (if copied on a proper synchronized product detector) after the first tube was over modulated in the negative direction. The voltage and power would be diverted to the upside down tube where sideband power would continue. There was trouble with the specific rule interpretation at the time in the FCC. Of course any of us today, would be able to see that the upside down tube's audio plate current and audio voltage must also be counted as part of the input power. But the FCC was having trouble deciding, at least as I understand it. At any rate, I think they got him for being outside the 40 meter band limits. You may remember more of the specifics on this Don. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Donald Chester Sent: Saturday, February 18, 2006 4:41 PM To: amradio@mailman.qth.net Subject: RE: [AMRadio] AM Transmitter Advice?? My understanding was. Under the old rules stage or stages, that provide output to the antenna, total power should not exceed 1000 watts DC input. This includes the sum of the driver and final in the case of GG output circuit. I think that rule was tested. I recall that was the rule. But it seems to me it was much ado about nothing. At most, the feedthrough power would be 10% of the total output power. How much signal strength gain could you get from increasing your power 10%? Of course, back in those days the FCC was very nitpicky about the ham rules, as they still are with broadcast stations. But they have shifted to the opposite approach with ham radio. Riley's efforts have rooted out the rottenest of the apples, but I suspect ham radio enforcement is still pretty low on the FCC's priority list, as long as the violations don't cause interference to other radio services. Since they changed the power rule, I have never heard of a SINGLE case of a ham receiving a citation for running too much p.e.p. Don K4KYV ___ 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
Re: [AMRadio] AM Transmitter Advice??
That was Fred, W3PHL. He built a high level balanced modulator (called the upside down tube circuit), and biased it to 600 watts carrier input. Then he applied a 2400 watt modulator to it. He used heavy clipping, like about 30 dB of clipping, and a low-level low-pass filter. At that time, plate power input to an AM transmitter was measured by the reaings of DC meters with approximately 0.25 second time constant. That time constant would make the meters read average voltage and current, which smoothed out SSB and controlled carrier signals. But on plate-modulated AM it did not read true power during modulation, because it was looking at average voltage and average current separately, while in AM the voltage and current are not separate, but they increase and decrease together, resulting in higher power input during modulation. Fred's X volts and Y milliamps held steady with or without modulation, looking like 600 watts input, even though easily 3 kilowatts of power were going to that final amp during modulation. The way plate input power was measured at that time, this was legal... so the FCC tried to nail him for overmodulation. Fred countered that overmodulation was a function of nonlinear distortion, and since his modulator correctly handled modulation beyond 100% negative, and it was not saturating at any point, it could not be said to be overmodulating. And if the FCC was going to consider this to be overmodulation, then what about all of theose guys on SSB and DSB... they would have to nail all of them for overmodulation, too! So the FCC resorted to nailing Fred on splatter out of band. It was a cheap trick, because Fred's signal was pretty clean. But they railroaded it through, and Fred lost his license for a year. When he came back on, he was using some fantastic Marconi high-level multi-pole filter, and there was no way they could accuse him of splattering out of the band. The FCC had lost interest by that time anyway, and they left Fred alone after that. But that high-level balanced modulator loophole was the reason that the FCC went for the PEP measurement technique in 1990. Theoretically, one could have used a modulator from a 500,000 watt broadcast station on a 1KW upside-down tube final, and it would have been legal. They couldn't have that! Darn it... Bacon, WA3WDR - Original Message - From: John E. Coleman (ARS WA5BXO) [EMAIL PROTECTED] To: 'Discussion of AM Radio' amradio@mailman.qth.net Sent: Saturday, February 18, 2006 6:39 PM Subject: RE: [AMRadio] AM Transmitter Advice?? Don, I have heard rumors of a citation or two but only in extreme cases such as 10 or 20 KW PEP and I don't know if the rumors are true. As I understand it the trick, that the FCC was to prevent, and someone was trying to get away with, was to run a 304TL with about 100 Volts on the plate in a GG configuration. Forward bias it to a high plate current like 1 Amp, so that it acts like a switch that is on. Then drive it with 5 KW PEP. It may have been some other some scenario as this but I think you get the picture. An Now, For Something Completely Different. Then there was the trick that a gentleman up in 3 land, I think, was going to run the high level double sideband reduced carrier generator type rig but he was not reducing the carrier just increasing the SBs via an extra upside down tube, as it was commonly called. The sideband power would continue to go up without distortion (if copied on a proper synchronized product detector) after the first tube was over modulated in the negative direction. The voltage and power would be diverted to the upside down tube where sideband power would continue. There was trouble with the specific rule interpretation at the time in the FCC. Of course any of us today, would be able to see that the upside down tube's audio plate current and audio voltage must also be counted as part of the input power. But the FCC was having trouble deciding, at least as I understand it. At any rate, I think they got him for being outside the 40 meter band limits. You may remember more of the specifics on this Don. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Donald Chester Sent: Saturday, February 18, 2006 4:41 PM To: amradio@mailman.qth.net Subject: RE: [AMRadio] AM Transmitter Advice?? My understanding was. Under the old rules stage or stages, that provide output to the antenna, total power should not exceed 1000 watts DC input. This includes the sum of the driver and final in the case of GG output circuit. I think that rule was tested. I recall that was the rule. But it seems to me it was much ado about nothing. At most, the feedthrough power would be 10% of the total output power. How much signal strength gain could you get from increasing your power 10%? Of course, back in those days the FCC was very nitpicky about the ham rules, as they still are with broadcast stations. But they have
Re: [AMRadio] AM Transmitter Advice??
Bacon, not trying to be contrite, but where in the old rules did the .25 second time constant appear? I have a copy of the old rules and don't see it. It says only that have the means. 73 Jim W5JO At that time, plate power input to an AM transmitter was measured by the reaings of DC meters with approximately 0.25 second time constant. That time constant would make the meters read average voltage and current, which smoothed out SSB and controlled carrier signals. But on plate-modulated AM it did not read true power during modulation, because it was looking at average voltage and average current separately, while in AM the voltage and current are not separate, but they increase and decrease together, resulting in higher power input during modulation.
Re: [AMRadio] AM Transmitter Advice??
Hi Jim... Hmm, it came from my sometimes flakey memory... I'm pretty sure there was a 0.25 second spec for the metering somewhere... maybe it was simply assumed that the meter time constant would be about 0.25 seconds. I suppose that if someone came up with a very slow meter, they could get away with huge SSB PEP, so it makes sense that the time constant of meter should be specified at least approximately. In any event, the FCC proceeded as though the DC volts multiplied by the DC amps gave the average power input - which was not true for AM. This Dc metering ignored the real power increase during modulation, permitting the upside down tube loophole. Now if guys like me had just kept their mouths shut about it, maybe the FCC wouldn't ever have caught on. But no, we had to throw it in the sidebanders' faces. I plead extreme youth at the time. Bacon, WA3WDR - Original Message - From: Jim Wilhite [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Saturday, February 18, 2006 7:28 PM Subject: Re: [AMRadio] AM Transmitter Advice?? Bacon, not trying to be contrite, but where in the old rules did the .25 second time constant appear? I have a copy of the old rules and don't see it. It says only that have the means. 73 Jim W5JO At that time, plate power input to an AM transmitter was measured by the reaings of DC meters with approximately 0.25 second time constant. That time constant would make the meters read average voltage and current, which smoothed out SSB and controlled carrier signals. But on plate-modulated AM it did not read true power during modulation, because it was looking at average voltage and average current separately, while in AM the voltage and current are not separate, but they increase and decrease together, resulting in higher power input during modulation. ___ ___ 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??
My memory is getting old, and it was always a little flakey, but I really seem to remember that there was, at least at one time, an FCC spec on the time constant of the plate meters in amateur transmitters. I did a search, but all I could find was this hint: http://www.dproducts.be/Drake_Museum/l-4b.htm Drake L-4B Linear Amplifier Plate Current Meter time constant is consistent wit Bacon, WA3WDR - Original Message - From: Jim Wilhite [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Saturday, February 18, 2006 7:28 PM Subject: Re: [AMRadio] AM Transmitter Advice?? Bacon, not trying to be contrite, but where in the old rules did the .25 second time constant appear? I have a copy of the old rules and don't see it. It says only that have the means. 73 Jim W5JO At that time, plate power input to an AM transmitter was measured by the reaings of DC meters with approximately 0.25 second time constant. That time constant would make the meters read average voltage and current, which smoothed out SSB and controlled carrier signals. But on plate-modulated AM it did not read true power during modulation, because it was looking at average voltage and average current separately, while in AM the voltage and current are not separate, but they increase and decrease together, resulting in higher power input during modulation. ___ ___ 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??
John, WA5BXO wrote: As I understand it the trick, that the FCC was to prevent, and someone was trying to get away with, was to run a 304TL with about 100 Volts on the plate in a GG configuration. Forward bias it to a high plate current like 1 Amp, so that it acts like a switch that is on. Then drive it with 5 KW PEP. It may have been some other some scenario as this but I think you get the picture. I had never heard of that, but it makes sense that someone might try it. Then there was the trick that a gentleman up in 3 land, I think, was going to run the high level double sideband reduced carrier generator type rig but he was not reducing the carrier just increasing the SBs via an extra upside down tube, as it was commonly called. The sideband power would continue to go up without distortion (if copied on a proper synchronized product detector) after the first tube was over modulated in the negative direction. The voltage and power would be diverted to the upside down tube where sideband power would continue. There was trouble with the specific rule interpretation at the time in the FCC. Of course any of us today, would be able to see that the upside down tube's audio plate current and audio voltage must also be counted as part of the input power. But the FCC was having trouble deciding, at least as I understand it. At any rate, I think they got him for being outside the 40 meter band limits. You may remember more of the specifics on this Don. I knew the gentleman personally. It was Fred, W3PHL, near Phila, PA. I met him at many hamfests, and visited him one weekend back in about 1971. I saw his rig, but by that time he had converted it to a big SSB linear. He liked to ragchew with VK's and ZL's in the pre-dawn hours on 40m, using a 120 ft. high beam. He not only fought the FCC, but had to deal with a tower case as well (which he won). The loophole in the regulations was that the definition of power was DC input to the final. With the upside down tube circuit, he ran about 600 watts DC input, and then applied several kw of audio. The rig was basically a high-level balanced modulator, but with DC applied to one tube, which effectively unbalanced the modulation, he claimed it was a plate-modulated AM rig, and that the legal power measurement was limited to the DC input to the final. The signal was double-sideband reduced carrier, with several kilowatts in the sidebands and less than 500 watts carrier power. Althhough a synchronous dectector would have have taken full advantage of both sidebands, most of the people he worked actually used SSB receivers, and simply copied either USB or LSB, and used the carrier only as a pilot carrier for setting the frequency on their receiver. The FCC couldn't make up its mind on how to deal with the issue, even though they could have cited a rule on the books that limited modulation to 100%, and they could have said he was modulating over 100% in the positive direction, regardless of the fact that the signal was clean. Instead, they ended up citing him for splattering outside the 40m band. He liked to operate at 7290, and even though he had engineering data to prove that his signal met all FCC specifications regarding spurious sideband products, they said that the rules allow no detectable signal whatever outside the limits of the amateur band, and he had detectable sideband products above 7300, even though they might have been 50-60 dB down. I understand this whole thing was part of an ongoing feud between Fred and a SSB group that was competing for the frequency, and the issue was brought up when the SSB group complained to the FCC. They suspended Fred's licence for six months based on the citation for out-of-band distortion products. The FCC referenced that case when they railroaded through their p.e.p. power rule. Don K4KYV ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
Re: [AMRadio] AM Transmitter Advice??
Yep, I think it was a 6-month suspension, not a year as I stated earlier. (I plead slightly flakey memory.) Bacon, WA3WDR - Original Message - From: Donald Chester [EMAIL PROTECTED] To: amradio@mailman.qth.net Sent: Saturday, February 18, 2006 8:45 PM Subject: RE: [AMRadio] AM Transmitter Advice?? John, WA5BXO wrote: As I understand it the trick, that the FCC was to prevent, and someone was trying to get away with, was to run a 304TL with about 100 Volts on the plate in a GG configuration. Forward bias it to a high plate current like 1 Amp, so that it acts like a switch that is on. Then drive it with 5 KW PEP. It may have been some other some scenario as this but I think you get the picture. I had never heard of that, but it makes sense that someone might try it. Then there was the trick that a gentleman up in 3 land, I think, was going to run the high level double sideband reduced carrier generator type rig but he was not reducing the carrier just increasing the SBs via an extra upside down tube, as it was commonly called. The sideband power would continue to go up without distortion (if copied on a proper synchronized product detector) after the first tube was over modulated in the negative direction. The voltage and power would be diverted to the upside down tube where sideband power would continue. There was trouble with the specific rule interpretation at the time in the FCC. Of course any of us today, would be able to see that the upside down tube's audio plate current and audio voltage must also be counted as part of the input power. But the FCC was having trouble deciding, at least as I understand it. At any rate, I think they got him for being outside the 40 meter band limits. You may remember more of the specifics on this Don. I knew the gentleman personally. It was Fred, W3PHL, near Phila, PA. I met him at many hamfests, and visited him one weekend back in about 1971. I saw his rig, but by that time he had converted it to a big SSB linear. He liked to ragchew with VK's and ZL's in the pre-dawn hours on 40m, using a 120 ft. high beam. He not only fought the FCC, but had to deal with a tower case as well (which he won). The loophole in the regulations was that the definition of power was DC input to the final. With the upside down tube circuit, he ran about 600 watts DC input, and then applied several kw of audio. The rig was basically a high-level balanced modulator, but with DC applied to one tube, which effectively unbalanced the modulation, he claimed it was a plate-modulated AM rig, and that the legal power measurement was limited to the DC input to the final. The signal was double-sideband reduced carrier, with several kilowatts in the sidebands and less than 500 watts carrier power. Althhough a synchronous dectector would have have taken full advantage of both sidebands, most of the people he worked actually used SSB receivers, and simply copied either USB or LSB, and used the carrier only as a pilot carrier for setting the frequency on their receiver. The FCC couldn't make up its mind on how to deal with the issue, even though they could have cited a rule on the books that limited modulation to 100%, and they could have said he was modulating over 100% in the positive direction, regardless of the fact that the signal was clean. Instead, they ended up citing him for splattering outside the 40m band. He liked to operate at 7290, and even though he had engineering data to prove that his signal met all FCC specifications regarding spurious sideband products, they said that the rules allow no detectable signal whatever outside the limits of the amateur band, and he had detectable sideband products above 7300, even though they might have been 50-60 dB down. I understand this whole thing was part of an ongoing feud between Fred and a SSB group that was competing for the frequency, and the issue was brought up when the SSB group complained to the FCC. They suspended Fred's licence for six months based on the citation for out-of-band distortion products. The FCC referenced that case when they railroaded through their p.e.p. power rule. Don K4KYV ___ 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
Re: [AMRadio] AM Transmitter Advice??
Needless to say Bacon, when this was the standard, I wasn't in to looking up the specs. My memory was that the specifications were for taut band meters but I don't recall the FCC specifying a time constant for the manufacturers to meet. I don't think the ones used on the Knight Kit were compatible. Most meters of good manufacture such as Weston, Triplett and such were of the acceptable standard. Usually the government, who could not be partial to a particular brand, would specify the general accepted manufacturing brands. As I recall the meters you pointed out in the ad for the Drake L-4B were of that quality but others made meters as acceptable. As my flaky memory serves, only until the advent of the digital meters, did the specifications improve. But one could not read the peak in digital. This is my complaint about peak reading wattmeters. Capacitive hold meters are not accurate to the standard that can be called accurate. So now we have the LED reading type but I have never seen a specified range of volts that cause one LED to operate and the knee where the other illuminates. Oh well, just musing and following this topic and enjoying myself. 73 Jim W5JO - Original Message - From: Bob Bruhns [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Saturday, February 18, 2006 7:00 PM Subject: Re: [AMRadio] AM Transmitter Advice?? My memory is getting old, and it was always a little flakey, but I really seem to remember that there was, at least at one time, an FCC spec on the time constant of the plate meters in amateur transmitters.
Re: [AMRadio] AM Transmitter Advice??
But that high-level balanced modulator loophole was the reason that the FCC went for the PEP measurement technique in 1990. Theoretically, one could have used a modulator from a 500,000 watt broadcast station on a 1KW upside-down tube final, and it would have been legal. They couldn't have that! Darn it... They could have gone with average (mean) power output, as read with a 0.25 second time-constant meter, and the power limit would have been relevant to the actual signal strength, regardless of mode. That way we would have a level playing field. ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
Re: [AMRadio] AM Transmitter Advice??
Bacon, not trying to be contrite, but where in the old rules did the .25 second time constant appear? I have a copy of the old rules and don't see it. It says only that have the means. It was not stated in the rules, but the FCC declared in a public notice that they would use that measurement standard for enforcement purposes. I recall seeing it somewhere in a 1950's era QST or CQ. I believe it is also stated in the ARRL SSB handbook that was published in the late 50's to early 60's. It wasn't an issue until SSB came along. The equipment manufacturers began using p.e.p. to rate their linear amplifiers because p.e.p. inflated the power ratings by a factor of two. It looked more impressive in the ads to claim that an amplifer was rated at 2 kw (p.e.p. input) than one kw (average dc input). Kinda like the stereo amplifiers that were (are?) rated at some absurd power rating called peak music power which inflates the actual power by a factor of several times. I recall that the FTC went after some manufacturers sometime in the 1960's because they were overly inflating the power ratings of their stereo amps. Strictly speaking, the p.e.p. rule hurt SSB almost as much as AM, if the SSB amplifier is operated below the saturation (flat-topping) point. With most human voices, the average power is about 10 dB below the peak power, so that with 100% modulation, the average modulation is about 30%. That's why the average level using a V-U meter is set tor about 30%. So a clean SSB signal at 1500 watts p.e.p. should be putting out only about 150 honest-to-God watts to the antenna. Under the old rules it was legal to run a SSB amplifier at 1 kw average DC input, and let the peaks go where they may, as long as the signal was clean. That allowed maybe 600 watts r.m.s. output, if the amplifier had enough peak power capability to reach that power level without flat-topping. Of course, most slopbucket rigs fall far short, and flat-top long before they reach that level, and you hear the garbage 10-15 kHz on both sides of the signal. With ALC and speech processing, SSB can legally increase its average power to maybe 300-400 watts before splattering if everything is adjusted properly. k4kyv ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
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
RE: [AMRadio] AM Transmitter Advice??
I bet you a BC610 will out-peg a DX100 any day! Don't care what the numbers say... Grin! That 12AX7 linear amplifier sounds like more of a FUN project than a useful station accessory! Just WAIT until the experts start telling you it can't be done, you will only get 30% efficiency and all that jazz! LOL. 73 de AF4K, Bry On 17 Feb 2006 at 4:29, Jim Candela wrote: 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
Re: [AMRadio] AM Transmitter Advice??
Thats poppycock. Everyone knows if you reduce the output filtering, and use an all band, coax fed, off-center Windom it will be possible to transmit multi-band. If you have a 5 bands off the radiator that would, effectively, give you 150% efficiency. 5 bands x 30% = 150%. Think of the possibilities. Now who of then experts would dare say, Theres no free lunch. The numbers dont lie. Brian Carling wrote: I bet you a BC610 will out-peg a DX100 any day! Don't care what the numbers say... Grin! That 12AX7 linear amplifier sounds like more of a FUN project than a useful station accessory! Just WAIT until the experts start telling you it can't be done, you will only get 30% efficiency and all that jazz! LOL. 73 de AF4K, Bry On 17 Feb 2006 at 4:29, Jim Candela wrote: 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??
Hi Jim, My understanding was. Under the old rules stage or stages, that provide output to the antenna, total power should not exceed 1000 watts DC input. This includes the sum of the driver and final in the case of GG output circuit. I think that rule was tested. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Candela Sent: Friday, February 17, 2006 6:29 AM To: Discussion of AM Radio Subject: RE: [AMRadio] AM Transmitter Advice?? Hi All, 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
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
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??
Wow. Well, 6 watts to 20 watts is about 5.2 dB of increase. One night someone switched from 350 watts to 80 watts, about a 6.4 dB signal reduction. What a difference, he really fell into the atmospheric static. I'm always surprised at what a few dB can do. I know it's not supposed to work that way... so it's suprising. I guess we work at pretty low s/n, so we really see the diffference. Bacon, WA3WDR - Original Message - From: Gary Schafer [EMAIL PROTECTED] To: 'Discussion of AM Radio' amradio@mailman.qth.net Sent: Friday, February 17, 2006 11:36 AM Subject: 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
RE: [AMRadio] AM Transmitter Advice??
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/
RE: [AMRadio] AM Transmitter Advice??
I have heard from many AM ops that with the correct setup, a linear amp works great. Linear amps pre-date high level class-B plate modulators by many years. In the early days, the only kind of plate modulation that was known used class-A audio amplifiers. This usually was in the form of Heising constant current modulation, although series modulation was also sometimes used. Since the class A modulator worked at such low efficiency, better overall efficiency was attainable with linear rf amplification. The original class-B ratings for tubes was intended for rf linears. Sometime in the late 1920's, it occurred to someone that class-B linear amplification would work just as well for audio as for rf, and the class-B audio amplifier was developed. The unusual thing about this setup was the large audio transformer required. Many rf linears were single-ended, and depended on the fiywheel effect of the rf tank circuit to supply the missing half of the sinewave output. With class-B audio amplification, the tubes have to be in pushpull in order to reproduce both halves of the sinewave. Thus the well-known class B modulator came into being. Some of the earliest AM broadcast and ham transmitters, beyond the simple modulated oscillator, used linear amplifiers for the final. High level class B modulators didn't come into common use until about 1932 or 1933. There is an article in an early 30's QST describing how to build your own modulation transformer to use in a new class B modulator. Don k4kyv ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
Re: [AMRadio] AM Transmitter Advice??
Don, K4KYV said: Sometime in the late 1920's, it occurred to someone that class-B linear amplification would work just as well for audio as for rf, and the class-B audio amplifier was developed. The unusual thing about this setup was the large audio transformer required. Many rf linears were single-ended, and depended on the fiywheel effect of the rf tank circuit to supply the missing half of the sinewave output. With class-B audio amplification, the tubes have to be in pushpull in order to reproduce both halves of the sinewave. Thus the well-known class B modulator came into being. Interesting that you mention this Don. I just read where it was Art Collins and his group that came up with the idea of using Class B push-pull audio for Class C rf amplifier. I'm not a Collins aficionado but Joe, N3IBX gave me the book, The First Fifty Years of Collins to read and I found it very good reading. There was some self-promoting in there but I was mildly surprised when I learned Collins did discover the Class B P-P plate modulation scheme. Mod-U-Lator, Mike(y) W3SLK
Re: [AMRadio] AM Transmitter Advice??
I would like to jump in here, I have a converted solid state rig on 20 meters. It runs an adjusted level output of 100 to 650 watts on that band. It uses a derivative of the MRF-150 only requires 100 milliwatts of drive over the whole band. The only drawback if you can call it that is this unit is water cooled. YMMV Jim WB2FCN - Original Message - From: Jim candela [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Monday, January 30, 2006 8:36 PM Subject: RE: [AMRadio] AM Transmitter Advice?? Guys, I just looked up the MRF150. For the moment look at the characteristics below with a big AM final amplifier in mind. With a 300 watt Pd rating, this thing might do well as a efficiency amplifier (modulate the gate bias) to make 100 watts AM, and do so with room to spare. So with say 33% efficiency (SWAG), 300 watts DC input, you get 100 watts RF output with 200 watts Pd. With modulation the efficiency improves (doubles @100% modulation from sine wave tone input). If you do a conventional Class C high level modulated amplifier with say 150 watts Pd, and 75% efficiency (SWAG), that gives you 600 watts DC input X .75 = 450 watts RF output! There are tons of hi power solid state audio amplifiers around, so there is your modulator too! Sure, the application notes dwell on SSB linear usage, but heck if it works on SSB, you can make it work on AM! Regards, Jim So how much do these things cost? :-) MRF150 MAXIMUM RATINGS Drain-Source Voltage VDSS 125 Vdc Drain-Gate Voltage VDGO 125 Vdc Gate-Source Voltage VGS ±40 Vdc Drain Current - Continuous ID 16 Adc Total Device Dissipation @ TC = 25°C Derate above 25°C PD 300 1.71 W/°C Storage Temperature Range Tstg -65 to +150 °C Operating Junction Temperature TJ 200 °C MOTOROLA RF DEVICE DATA ELECTRICAL CHARACTERISTICS (TC = 25°C unless otherwise noted.) Characteristic Symbol Min Typ Max Unit OFF CHARACTERISTICS Drain-Source Breakdown Voltage (VGS = 0, ID = 100 mA) V(BR)DSS 125 - - Vdc Zero Gate Voltage Drain Current (VDS = 50 V, VGS = 0) IDSS - - 5.0 mAdc Gate-Body Leakage Current (VGS = 20 V, VDS = 0) IGSS - - 1.0 mAdc ON CHARACTERISTICS Gate Threshold Voltage (VDS = 10 V, ID = 100 mA) VGS(th) 1.0 3.0 5.0 Vdc Drain-Source On-Voltage (VGS = 10 V, ID = 10 A) VDS(on) 1.0 3.0 5.0 Vdc Forward Transconductance (VDS = 10 V, ID = 5.0 A) gfs 4.0 7.0 - mhos DYNAMIC CHARACTERISTICS Input Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz) Ciss - 400 - pF Output Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz) Coss - 240 - pF Reverse Transfer Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz) Crss - 40 - pF FUNCTIONAL TESTS (SSB) Common Source Amplifier Power Gain f = 30 MHz (VDD = 50 V, Pout = 150 W (PEP), IDQ = 250 mA) f = 150 MHz Full data sheet: http://www.twhrf.net/mkic/mrf150.pdf -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Jim candela Sent: Monday, January 30, 2006 6:54 PM To: Discussion of AM Radio Subject: RE: [AMRadio] AM Transmitter Advice?? Larry, I am interested in what your friend Jim, KR1S has in mind for that 100 watt AM solid state exciter for 75 meters. Is that carrier output, or PEP? In thinking about it, this could vary from a scaled up CB rig with a tuned class C final with high level modulation, or maybe a small AM exciter with a solid state push pull linear, or maybe a class E setup. We seemed to get side tracked on the 813 amp idea, and glossed over the exciter concept you laid out. How about a nice juicy MRF-150 with high level drain modulation, or low level gate bias modulation? I bet no one has ever tried it either way.. Regards, Jim WD5JKO [mailto:[EMAIL PROTECTED] Behalf Of Larry Keith My friend, KR1S (Jim Kearman) is designing an AM transceiver, for me. We plan for this to be a solid-state unit that will deliver about 100 watts out. It will be single band (75 meters) and I have been considering using that to feed a homebrew linear. I have the makings of a 2 x 813 amp thanks to my and Jim's hamfesting efforts. Larry KQBY Larry Keith -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.23/243 - Release Date: 1/27/2006 __ 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 -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.23/243 - Release Date: 1/27/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.23/243 - Release Date: 1/27/2006 __ AMRadio
RE: [AMRadio] AM Transmitter Advice??
I based my 813 rig on the article you talk about. I did not do separate output decks but wound up with a continuous coverage 1.5 to 30 mc setup. A lot of the electronics (control, protection) I got from that design though. That article was very interesting, the decks wind up being quite small. My modulator deck came right out of a QST article, pair of 4cx250b's with minor changes. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of W1EOF Sent: Monday, January 30, 2006 4:14 PM To: Todd, KA1KAQ; Discussion of AM Radio Subject: RE: [AMRadio] AM Transmitter Advice?? No problem with them mounted horizontally if in the correct plane. Example: For years in the ARRL handbook 1960s there was an article that described separate 813x2 amp for each band, all rack mounted. As a young ham in the early 70s I would looke that and drool. The 813 is a great tube, certainly very high on the watt-per-dollar chart. It's always been one of my favorites along with the 810, 4-400, and the 4-125. I always thought the 4-125 would be great as a final for a say... 350W CW transmitter. Like the T-9er, but with more power out. Anyone needing projects, or potential projects email me off-list. No charge, I will give them away to a good home. 73, Mark W1EOF -Original Message- From: Todd, KA1KAQ [mailto:[EMAIL PROTECTED] Sent: Monday, January 30, 2006 3:46 PM To: [EMAIL PROTECTED]; Discussion of AM Radio Subject: Re: [AMRadio] AM Transmitter Advice?? On 1/30/06, W1EOF [EMAIL PROTECTED] wrote: I agree with Larry. I've been collecting the pieces for a 813x2 desktop amp for awhile now. I'm almost ready to begin. Hmmm... interesting. I actually have a nice horizontally-mounted CW 813 transmitter sitting up over the garage. I wonder what it would take to add a modulator? I chuffed it into a Globe King cabinet because I wanted to use the rack for something else, and there it sits. Yesterday while I was playing around at building a homebrew (ala Don Chester) 40 meter dipole, I was listening on 40 to a few guys discussing the venerable 813. One of them was Tom M...Marcellano? W3BYM (I think). He's written a fair number of articles for ER as I recall, probably a few about 813 rigs. I think he said it was his favorite tube and had nothing but praise for it. At least one of the other guys either had or was running a 813 rig also. Wish now that I'd paid more attention, but it might've resulted in soldering my finger instead of the antenna. Has anyone ever mounted them horizontally to save space? I can't remember if it's a single tube or a pair. Sure is compact. Power supply is in the garage because it was too heavy to haul upstairs. Looks like a Beastly 610 transformer on the chassis. As an aside, I think K1JJ Tom is still building a rig with a pair of 813s blown through Dietz lantern globes as chimneys. There were pictures of it on amfone not long ago. de Todd/'Boomer' KA1KAQ -- 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
[AMRadio] AM Transmitter Advice??
Well, Let's see if we can change the subject.. 8-) I am gathering ideas for a homebrew AM transmitter.. My friend, KR1S (Jim Kearman) is designing an AM transceiver, for me. We plan for this to be a solid-state unit that will deliver about 100 watts out. It will be single band (75 meters) and I have been considering using that to feed a homebrew linear. I have the makings of a 2 x 813 amp thanks to my and Jim's hamfesting efforts. So far, we have been reading and kicking around ideas. It seems that with the derating of the amp to handle the continuous carrier, etc.. may be more trouble than it is worth. So, I would be interested in opinions as to the relative merits of using a linear vs high-level modulation. And, pointers to existing circuits would be helpful.. Any ideas? 73, Larry KQBY Larry Keith 231 Shenandoah Trail Warner Robins, GA 31088-6289 [EMAIL PROTECTED] 478-329-0030 (home) __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
Re: [AMRadio] AM Transmitter Advice??
Larry for years I used a pair of 813's in grounded grid and drove them with a ranger. It produced great sounding audio. I still have that as my backup to my globe king. 813's are great tubes. The only drawback for me is I like to operate on ten meters and 813's are shakey at best, up there. good luck on your project, Iknow you will enjoy it. ronnie - W5SUM -- Original Message --- From: Larry Keith [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Mon, 30 Jan 2006 12:06:43 -0800 (PST) Subject: [AMRadio] AM Transmitter Advice?? Well, Let's see if we can change the subject.. 8-) I am gathering ideas for a homebrew AM transmitter.. My friend, KR1S (Jim Kearman) is designing an AM transceiver, for me. We plan for this to be a solid-state unit that will deliver about 100 watts out. It will be single band (75 meters) and I have been considering using that to feed a homebrew linear. I have the makings of a 2 x 813 amp thanks to my and Jim's hamfesting efforts. So far, we have been reading and kicking around ideas. It seems that with the derating of the amp to handle the continuous carrier, etc.. may be more trouble than it is worth. So, I would be interested in opinions as to the relative merits of using a linear vs high-level modulation. And, pointers to existing circuits would be helpful.. Any ideas? 73, Larry KQBY Larry Keith 231 Shenandoah Trail Warner Robins, GA 31088-6289 [EMAIL PROTECTED] 478-329-0030 (home) __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com __ 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 --- End of Original Message ---
RE: [AMRadio] AM Transmitter Advice??
I agree with Larry. I've been collecting the pieces for a 813x2 desktop amp for awhile now. I'm almost ready to begin. I have heard from many AM ops that with the correct setup, a linear amp works great. As for the operation of 813s on 10M, Ronnie is correct that some people have had trouble there. I have some information from a ham who built an amp that runs from 160 - 10M. All it took was specific consideration of the interelectrode capacitance on 10M. If you are really interested I could email you the scans he sent me (once I get an OK from him). Best of luck on it and please keep us all informed as to your progress! 73, Mark W1EOF -Original Message- From: ronnie.hull [mailto:[EMAIL PROTECTED] Sent: Monday, January 30, 2006 3:11 PM To: Discussion of AM Radio Subject: Re: [AMRadio] AM Transmitter Advice?? Larry for years I used a pair of 813's in grounded grid and drove them with a ranger. It produced great sounding audio. I still have that as my backup to my globe king. 813's are great tubes. The only drawback for me is I like to operate on ten meters and 813's are shakey at best, up there. good luck on your project, Iknow you will enjoy it. ronnie - W5SUM -- Original Message --- From: Larry Keith [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Mon, 30 Jan 2006 12:06:43 -0800 (PST) Subject: [AMRadio] AM Transmitter Advice?? Well, Let's see if we can change the subject.. 8-) I am gathering ideas for a homebrew AM transmitter.. My friend, KR1S (Jim Kearman) is designing an AM transceiver, for me. We plan for this to be a solid-state unit that will deliver about 100 watts out. It will be single band (75 meters) and I have been considering using that to feed a homebrew linear. I have the makings of a 2 x 813 amp thanks to my and Jim's hamfesting efforts. So far, we have been reading and kicking around ideas. It seems that with the derating of the amp to handle the continuous carrier, etc.. may be more trouble than it is worth. So, I would be interested in opinions as to the relative merits of using a linear vs high-level modulation. And, pointers to existing circuits would be helpful.. Any ideas? 73, Larry KQBY Larry Keith 231 Shenandoah Trail Warner Robins, GA 31088-6289 [EMAIL PROTECTED] 478-329-0030 (home) __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com __ 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 --- End of Original Message --- __ 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 -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.22/239 - Release Date: 1/24/06 -- 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
Re: [AMRadio] AM Transmitter Advice??
On 1/30/06, W1EOF [EMAIL PROTECTED] wrote: I agree with Larry. I've been collecting the pieces for a 813x2 desktop amp for awhile now. I'm almost ready to begin. Hmmm... interesting. I actually have a nice horizontally-mounted CW 813 transmitter sitting up over the garage. I wonder what it would take to add a modulator? I chuffed it into a Globe King cabinet because I wanted to use the rack for something else, and there it sits. Yesterday while I was playing around at building a homebrew (ala Don Chester) 40 meter dipole, I was listening on 40 to a few guys discussing the venerable 813. One of them was Tom M...Marcellano? W3BYM (I think). He's written a fair number of articles for ER as I recall, probably a few about 813 rigs. I think he said it was his favorite tube and had nothing but praise for it. At least one of the other guys either had or was running a 813 rig also. Wish now that I'd paid more attention, but it might've resulted in soldering my finger instead of the antenna. Has anyone ever mounted them horizontally to save space? I can't remember if it's a single tube or a pair. Sure is compact. Power supply is in the garage because it was too heavy to haul upstairs. Looks like a Beastly 610 transformer on the chassis. As an aside, I think K1JJ Tom is still building a rig with a pair of 813s blown through Dietz lantern globes as chimneys. There were pictures of it on amfone not long ago. de Todd/'Boomer' KA1KAQ
RE: [AMRadio] AM Transmitter Advice??
No problem with them mounted horizontally if in the correct plane. Example: For years in the ARRL handbook 1960s there was an article that described separate 813x2 amp for each band, all rack mounted. As a young ham in the early 70s I would looke that and drool. The 813 is a great tube, certainly very high on the watt-per-dollar chart. It's always been one of my favorites along with the 810, 4-400, and the 4-125. I always thought the 4-125 would be great as a final for a say... 350W CW transmitter. Like the T-9er, but with more power out. Anyone needing projects, or potential projects email me off-list. No charge, I will give them away to a good home. 73, Mark W1EOF -Original Message- From: Todd, KA1KAQ [mailto:[EMAIL PROTECTED] Sent: Monday, January 30, 2006 3:46 PM To: [EMAIL PROTECTED]; Discussion of AM Radio Subject: Re: [AMRadio] AM Transmitter Advice?? On 1/30/06, W1EOF [EMAIL PROTECTED] wrote: I agree with Larry. I've been collecting the pieces for a 813x2 desktop amp for awhile now. I'm almost ready to begin. Hmmm... interesting. I actually have a nice horizontally-mounted CW 813 transmitter sitting up over the garage. I wonder what it would take to add a modulator? I chuffed it into a Globe King cabinet because I wanted to use the rack for something else, and there it sits. Yesterday while I was playing around at building a homebrew (ala Don Chester) 40 meter dipole, I was listening on 40 to a few guys discussing the venerable 813. One of them was Tom M...Marcellano? W3BYM (I think). He's written a fair number of articles for ER as I recall, probably a few about 813 rigs. I think he said it was his favorite tube and had nothing but praise for it. At least one of the other guys either had or was running a 813 rig also. Wish now that I'd paid more attention, but it might've resulted in soldering my finger instead of the antenna. Has anyone ever mounted them horizontally to save space? I can't remember if it's a single tube or a pair. Sure is compact. Power supply is in the garage because it was too heavy to haul upstairs. Looks like a Beastly 610 transformer on the chassis. As an aside, I think K1JJ Tom is still building a rig with a pair of 813s blown through Dietz lantern globes as chimneys. There were pictures of it on amfone not long ago. de Todd/'Boomer' KA1KAQ -- 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
RE: [AMRadio] AM Transmitter Advice??
A pair of 813's at 2000 volts and 400 ma will give you 600 to 700 watts of carrier output, and will be running easy. You would need a 400 watt modulator or better, I use a pair of 4x150a tubes in ab1, good for 600 watts of audio at 2000 volts. If you want single band operation, all you need to do is wind a tank coil out of copper tubing. For a simple, well working cheap and easy transmitter, its hard to beat a pair of 812a's modulated by a pair of 811a's. At 1500 volts, you get 300 watts out. Triodes can modulate nicely, no screens to worry about modulating. The 811/812 tubes are cheap, and in push pull link output, are stable and easy to do. I use the kilowatt plug in coils, so I can change bands if I want to. Easy way is to build a class C rf deck and excite it with a rice box, build a modulator and drive it with an 8 ohm output. 20 watts of audio will drive most modulator tube grids more then enough. I never liked the amp route, loads of power input and big tubes running hot, for little AM power output, and every amp adds distortion. Amps are great for ssb, but add a carrier and they are not so great. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Larry Keith Sent: Monday, January 30, 2006 3:07 PM To: Discussion of AM Radio Subject: [AMRadio] AM Transmitter Advice?? Well, Let's see if we can change the subject.. 8-) I am gathering ideas for a homebrew AM transmitter.. My friend, KR1S (Jim Kearman) is designing an AM transceiver, for me. We plan for this to be a solid-state unit that will deliver about 100 watts out. It will be single band (75 meters) and I have been considering using that to feed a homebrew linear. I have the makings of a 2 x 813 amp thanks to my and Jim's hamfesting efforts. So far, we have been reading and kicking around ideas. It seems that with the derating of the amp to handle the continuous carrier, etc.. may be more trouble than it is worth. So, I would be interested in opinions as to the relative merits of using a linear vs high-level modulation. And, pointers to existing circuits would be helpful.. Any ideas? 73, Larry KQBY Larry Keith 231 Shenandoah Trail Warner Robins, GA 31088-6289 [EMAIL PROTECTED] 478-329-0030 (home) __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com __ 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??
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 *** Original message dated 1/30/06 12:08:03 PM, [EMAIL PROTECTED] writes (in part): My friend, KR1S (Jim Kearman) is designing an AM transceiver, for me. We plan for this to be a solid-state unit that will deliver about 100 watts out. It will be single band (75 meters) and I have been considering using that to feed a homebrew linear. I have the makings of a 2 x 813 amp thanks to my and Jim's hamfesting efforts. So far, we have been reading and kicking around ideas. It seems that with the derating of the amp to handle the continuous carrier, etc.. may be more trouble than it is worth.
RE: [AMRadio] AM Transmitter Advice??
He is telling you that a pair of 813's as a linear are good for only 125 watts of carrier output on AM and that it takes tubes with at least 800 watts plate dissipation to run the legal limit on AM linear. 73 Gary K4FMX 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of W1EOF Sent: Monday, January 30, 2006 5:36 PM To: Discussion of AM Radio Subject: RE: [AMRadio] AM Transmitter Advice?? Dennis, I was with you until the end where you say: Bottom line -- If you're going to build a linear do it right and go for a pair of 4-400's, single 4- 1000A, 3-1000Z or one of the big Russian tubes I've seen on eBay recently. Assuming one is going to build a linear, and so putting aside other issues such as linear vs plate modulation, why do you think it makes a difference what tube is used? Are you referring to running a linear at greater than legal limit?. 73, Mark W1EOF -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Monday, January 30, 2006 5:01 PM To: [EMAIL PROTECTED] Cc: amradio@mailman.qth.net Subject: Re: [AMRadio] AM Transmitter Advice?? Linears for AM -- here we go again for at least the third time in the past 12 months. Basic considerations: 1. Under carrier only conditions a correctly designed and adjusted linear amplifier will be operating at about 33% efficiency. So, with a pair of 813's the math works out to 125 watts of carrier, obviously not worth the effort if you're starting off with a 100 W carrier exciter. 2. The linear must be initially tuned up at the peak RF output value which, in turn, requires that the exciter (or some other source) must be capable of providing the input necessary to do this. Typically, his would be 4 times the carrier value but expect to hear a lot more on this from the asymmetrical speech waveform crowd. 3. Real AM can only come from a plate modulated class C PA in the view of certain members of this community. At the same time, big mod iron is expensive and hard to find. Also, for a legal max rig the wall plug efficiency of high level and linear is not that much different in the final analysis. Bottom line -- If you're going to build a linear do it right and go for a pair of 4-400's, single 4-1000A, 3-1000Z or one of the big Russian tubes I've seen on eBay recently. I use my HB 3-1000Z amp on both SSB and AM, BTW. Works FB. Good luck with the project. Dennis D. W7QHO Glendale, CA -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.22/239 - Release Date: 1/24/06 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
Re: [AMRadio] AM Transmitter Advice??
Gary, Thanks. Dennis D. W7QHO Glendale, CA
RE: [AMRadio] AM Transmitter Advice??
Larry, I am interested in what your friend Jim, KR1S has in mind for that 100 watt AM solid state exciter for 75 meters. Is that carrier output, or PEP? In thinking about it, this could vary from a scaled up CB rig with a tuned class C final with high level modulation, or maybe a small AM exciter with a solid state push pull linear, or maybe a class E setup. We seemed to get side tracked on the 813 amp idea, and glossed over the exciter concept you laid out. How about a nice juicy MRF-150 with high level drain modulation, or low level gate bias modulation? I bet no one has ever tried it either way.. Regards, Jim WD5JKO [mailto:[EMAIL PROTECTED] Behalf Of Larry Keith My friend, KR1S (Jim Kearman) is designing an AM transceiver, for me. We plan for this to be a solid-state unit that will deliver about 100 watts out. It will be single band (75 meters) and I have been considering using that to feed a homebrew linear. I have the makings of a 2 x 813 amp thanks to my and Jim's hamfesting efforts. Larry KQBY Larry Keith -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.23/243 - Release Date: 1/27/2006
RE: [AMRadio] AM Transmitter Advice??
Guys, I just looked up the MRF150. For the moment look at the characteristics below with a big AM final amplifier in mind. With a 300 watt Pd rating, this thing might do well as a efficiency amplifier (modulate the gate bias) to make 100 watts AM, and do so with room to spare. So with say 33% efficiency (SWAG), 300 watts DC input, you get 100 watts RF output with 200 watts Pd. With modulation the efficiency improves (doubles @100% modulation from sine wave tone input). If you do a conventional Class C high level modulated amplifier with say 150 watts Pd, and 75% efficiency (SWAG), that gives you 600 watts DC input X .75 = 450 watts RF output! There are tons of hi power solid state audio amplifiers around, so there is your modulator too! Sure, the application notes dwell on SSB linear usage, but heck if it works on SSB, you can make it work on AM! Regards, Jim So how much do these things cost? :-) MRF150 MAXIMUM RATINGS DrainSource Voltage VDSS 125 Vdc DrainGate Voltage VDGO 125 Vdc GateSource Voltage VGS ±40 Vdc Drain Current Continuous ID 16 Adc Total Device Dissipation @ TC = 25°C Derate above 25°C PD 300 1.71 W/°C Storage Temperature Range Tstg 65 to +150 °C Operating Junction Temperature TJ 200 °C MOTOROLA RF DEVICE DATA ELECTRICAL CHARACTERISTICS (TC = 25°C unless otherwise noted.) Characteristic Symbol Min Typ Max Unit OFF CHARACTERISTICS DrainSource Breakdown Voltage (VGS = 0, ID = 100 mA) V(BR)DSS 125 Vdc Zero Gate Voltage Drain Current (VDS = 50 V, VGS = 0) IDSS 5.0 mAdc GateBody Leakage Current (VGS = 20 V, VDS = 0) IGSS 1.0 mAdc ON CHARACTERISTICS Gate Threshold Voltage (VDS = 10 V, ID = 100 mA) VGS(th) 1.0 3.0 5.0 Vdc DrainSource OnVoltage (VGS = 10 V, ID = 10 A) VDS(on) 1.0 3.0 5.0 Vdc Forward Transconductance (VDS = 10 V, ID = 5.0 A) gfs 4.0 7.0 mhos DYNAMIC CHARACTERISTICS Input Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz) Ciss 400 pF Output Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz) Coss 240 pF Reverse Transfer Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz) Crss 40 pF FUNCTIONAL TESTS (SSB) Common Source Amplifier Power Gain f = 30 MHz (VDD = 50 V, Pout = 150 W (PEP), IDQ = 250 mA) f = 150 MHz Full data sheet: http://www.twhrf.net/mkic/mrf150.pdf -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Jim candela Sent: Monday, January 30, 2006 6:54 PM To: Discussion of AM Radio Subject: RE: [AMRadio] AM Transmitter Advice?? Larry, I am interested in what your friend Jim, KR1S has in mind for that 100 watt AM solid state exciter for 75 meters. Is that carrier output, or PEP? In thinking about it, this could vary from a scaled up CB rig with a tuned class C final with high level modulation, or maybe a small AM exciter with a solid state push pull linear, or maybe a class E setup. We seemed to get side tracked on the 813 amp idea, and glossed over the exciter concept you laid out. How about a nice juicy MRF-150 with high level drain modulation, or low level gate bias modulation? I bet no one has ever tried it either way.. Regards, Jim WD5JKO [mailto:[EMAIL PROTECTED] Behalf Of Larry Keith My friend, KR1S (Jim Kearman) is designing an AM transceiver, for me. We plan for this to be a solid-state unit that will deliver about 100 watts out. It will be single band (75 meters) and I have been considering using that to feed a homebrew linear. I have the makings of a 2 x 813 amp thanks to my and Jim's hamfesting efforts. Larry KQBY Larry Keith -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.23/243 - Release Date: 1/27/2006 __ 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 -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.23/243 - Release Date: 1/27/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.23/243 - Release Date: 1/27/2006
Re: [AMRadio] AM Transmitter Advice??
- Original Message - I am gathering ideas for a homebrew AM transmitter.. If you are interested in solid state, a gold mine of information can be had from the Class E Web site. There is a link to it on www.amfone.net. Using plans on that site, you can build a legal-limit AM transmitter that will sound great while taking up only a foot or two of rack space. Class E is used in the current generation of AM broadcast transmitters. It is very efficient (90%) and Steve Cloutier's designs on the Web site provide excellent performance on positive modulation peaks. Good luck with your project! Phil Galasso K2PG
