Re: [AMRadio] GG 813 Linear in GE Ham News
I think I'll go back to 6L6's ;-) Jim candela wrote: I'd like to clarify one item I mentioned yesterday. When Geoff W5OMR took possession of those 8417's, he had absolutely no idea what crimes had been committed decades earlier while using those same two tubes. Those are tough tubes (GE that is). Now the evidence is in another unsuspecting hams hamshack! :-) Jim Candela wrote: I once knew a Novice ham about 30 years ago who modified a Viking I to have an external power supply for the modulator, and 8417 modulator tubes. This thing could really modulate that 4D32. One lonely day the thing was put on 11 meters, and the 5R4's were removed so there was NO B+ or screen voltage to the final RF amp...that is until the modulator was driven. This produced a very distorted and effective jammer that occupied all 23 channels and then some. Another ham cam by who could play the harmonica. You could say this was DSB without carrier, and overdriven to the limit for maximum splatter effect. I forget the name of that troublemaker, but my good buddy W5OMR is using those same two 8417 tubes today in his Titanic speech amplifier. Jim
RE: [AMRadio] GG 813 Linear in GE Ham News
I'd like to clarify one item I mentioned yesterday. When Geoff W5OMR took possession of those 8417's, he had absolutely no idea what crimes had been committed decades earlier while using those same two tubes. Those are tough tubes (GE that is). Now the evidence is in another unsuspecting hams hamshack! :-) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Jim candela Sent: Monday, October 10, 2005 7:01 PM To: Discussion of AM Radio Subject: RE: [AMRadio] GG 813 Linear in GE Ham News I once knew a Novice ham about 30 years ago who modified a Viking I to have an external power supply for the modulator, and 8417 modulator tubes. This thing could really modulate that 4D32. One lonely day the thing was put on 11 meters, and the 5R4's were removed so there was NO B+ or screen voltage to the final RF amp...that is until the modulator was driven. This produced a very distorted and effective jammer that occupied all 23 channels and then some. Another ham cam by who could play the harmonica. You could say this was DSB without carrier, and overdriven to the limit for maximum splatter effect. I forget the name of that troublemaker, but my good buddy W5OMR is using those same two 8417 tubes today in his Titanic speech amplifier. Jim -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Donald Chester Sent: Sunday, October 09, 2005 12:49 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] GG 813 Linear in GE Ham News >This scheme is also taken even further into the cutoff region in CB-land >and used to obtain a low level carrier, say 1 watt, while still obtaining >12 watts peak envelope levels at full modulation. A radio or amplifier set >up to do this is called a 'modulator', and gets you alot of 'swing' on the >old power meter. And gets you a lot of splatter and distortion too. -DC __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.13/124 - Release Date: 10/7/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.13/126 - Release Date: 10/9/2005 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.13/126 - Release Date: 10/9/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.14/128 - Release Date: 10/10/2005
RE: [AMRadio] GG 813 Linear in GE Ham News
I once knew a Novice ham about 30 years ago who modified a Viking I to have an external power supply for the modulator, and 8417 modulator tubes. This thing could really modulate that 4D32. One lonely day the thing was put on 11 meters, and the 5R4's were removed so there was NO B+ or screen voltage to the final RF amp...that is until the modulator was driven. This produced a very distorted and effective jammer that occupied all 23 channels and then some. Another ham cam by who could play the harmonica. You could say this was DSB without carrier, and overdriven to the limit for maximum splatter effect. I forget the name of that troublemaker, but my good buddy W5OMR is using those same two 8417 tubes today in his Titanic speech amplifier. Jim -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Donald Chester Sent: Sunday, October 09, 2005 12:49 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] GG 813 Linear in GE Ham News >This scheme is also taken even further into the cutoff region in CB-land >and used to obtain a low level carrier, say 1 watt, while still obtaining >12 watts peak envelope levels at full modulation. A radio or amplifier set >up to do this is called a 'modulator', and gets you alot of 'swing' on the >old power meter. And gets you a lot of splatter and distortion too. -DC __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.13/124 - Release Date: 10/7/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.13/126 - Release Date: 10/9/2005
Re: [AMRadio] GG 813 Linear in GE Ham News
A standard carrier reading wattt meter (think 'Bird') should not move, when the carrier is modulated to 100%. A PEP reading wattmeter (it's my opinion that you can *not* find one that reads accuratly enough) willl only show that the rig -is- being modulated, but not if it is being over-modulated, causing distortion and splatter and being rather un-neighborly to others on near frequencies.. A field strength meter should not move when the carrier is modulated to 100%. It is designed to read AVERAGE carrier voltage. If the final stage has good modulation linearity, the average carrier voltage doesn't change up to 100% modualtion. A true average-reading wattmeter will read increased output with modulation. The power output includes carrier + sideband power. 1000 watts carrier output should read 1500 (average, or mean) watts out with 100% sinewave modulation. With a thermocouple rf ammeter in the line, the rf current at the output should show a 22.5% increase with 100% sinusoidal modulation. Many rf output meters actually read rf voltage output and therefore show no upward kick with modualtion. An rf ammeter is a thermal device which does not average the output, so it will show an upward kick with modulation. Square the current increase to get the percent power increase. Don k4kyv
Re: [AMRadio] GG 813 Linear in GE Ham News
Donald Chester wrote: This scheme is also taken even further into the cutoff region in CB-land and used to obtain a low level carrier, say 1 watt, while still obtaining 12 watts peak envelope levels at full modulation. A radio or amplifier set up to do this is called a 'modulator', and gets you alot of 'swing' on the old power meter. And gets you a lot of splatter and distortion too. Because, a truely 100% modulated AM carrier doesn't move, on the watt meter. The output RF current will increase a bit when modulated, but the actual carrier level doesn't/shouldn't move when modulated. When modulation levels exceeds 100%, the plate voltage on the final is reduced to 0 at that momemt. If you exceed 100% (negative peaks to/past the baseline, while watching the carrier envelope on a scope), then the audio voltage then adds to the carrier output. One might think that this is desireable, but remember that spatter and distortion occur the instant the negative peaks exceed the carrier level. A standard carrier reading wattt meter (think 'Bird') should not move, when the carrier is modulated to 100%. A PEP reading wattmeter (it's my opinion that you can *not* find one that reads accuratly enough) willl only show that the rig -is- being modulated, but not if it is being over-modulated, causing distortion and splatter and being rather un-neighborly to others on near frequencies.. I know I've said this before, and it just needs saying again... Don Chester/K4KYV was quoted years and years ago in the AM Press Exchange (AM P/X) as saying: "Operating your AM Rig without an Oscilliscope, is like driving your car at night without headlights." -- 73 = Best Regards, -Geoff/W5OMR
RE: [AMRadio] GG 813 Linear in GE Ham News
This scheme is also taken even further into the cutoff region in CB-land and used to obtain a low level carrier, say 1 watt, while still obtaining 12 watts peak envelope levels at full modulation. A radio or amplifier set up to do this is called a 'modulator', and gets you alot of 'swing' on the old power meter. And gets you a lot of splatter and distortion too. -DC
RE: [AMRadio] GG 813 Linear in GE Ham News
This scheme is also taken even further into the cutoff region in CB-land and used to obtain a low level carrier, say 1 watt, while still obtaining 12 watts peak envelope levels at full modulation. A radio or amplifier set up to do this is called a 'modulator', and gets you alot of 'swing' on the old power meter. Just don't take it too far. PJ > >>> >I increased the bias on it so to the point just > >> beyond cutoff for AM so > >>> >that >>> >it requires a little more to drive and it reaches > >> negative 100% modulation > >>> >slightly before the driver does.
RE: [AMRadio] GG 813 Linear in GE Ham News
Don, I have heard the term, "class BC". Is this what you are referring to? Jim --- Donald Chester <[EMAIL PROTECTED]> wrote: > > >I have an SB200 linear and on AM it is equivalent > to a DX100. > >I increased the bias on it so to the point just > beyond cutoff for AM so > >that > >it requires a little more to drive and it reaches > negative 100% modulation > >slightly before the driver does. But this seemed > to help the modulation > >linearity and efficiency just a little. > > That's an old trick that I first read about in a > 1930's RADIO article. > Overbias the AM linear to increase the negative peak > modulation percentage. > > It also can have a distortion advantage, especially > if the modulator driver > stage uses grid modulation. Most grid modulated > finals become nonlinear > near 100% negative modulation, or are simply > incapable of cutting the > carrier off completely, so to maintain good > modulation linearity, limit the > modulation to 90% or less in the negative direction, > then overbias the > linear output stage until the negative peaks in the > output reach near 100%. > This will retain modulationr linearaty on negative > peaks and reduce overall > distortion levels. > > > __ > AMRadio mailing list > Home: > http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami >
RE: [AMRadio] GG 813 Linear in GE Ham News
I have an SB200 linear and on AM it is equivalent to a DX100. I increased the bias on it so to the point just beyond cutoff for AM so that it requires a little more to drive and it reaches negative 100% modulation slightly before the driver does. But this seemed to help the modulation linearity and efficiency just a little. That's an old trick that I first read about in a 1930's RADIO article. Overbias the AM linear to increase the negative peak modulation percentage. It also can have a distortion advantage, especially if the modulator driver stage uses grid modulation. Most grid modulated finals become nonlinear near 100% negative modulation, or are simply incapable of cutting the carrier off completely, so to maintain good modulation linearity, limit the modulation to 90% or less in the negative direction, then overbias the linear output stage until the negative peaks in the output reach near 100%. This will retain modulationr linearaty on negative peaks and reduce overall distortion levels.
Re: [AMRadio] GG 813 Linear in GE Ham News -12AT7 12AX7
Wow, 8W of audio from a 12AX7. I assume the distortion is pretty high at full output. 8W, 8K p-p, that's pushing the specs with a 12AX7, because of cathode emission and plate dissipation. And with zero bias, you would need to set up a phase splitter that that can provide grid current. I guess it's possible, but I'd try a 12AU7 or preferably a 12BH7 at 300V with -20V grid bias in class B1. Cathode emission 6SN7 filament: 6.3V 0.6A, 3.78W filament power, 70mA cathode emission per tube. 90 mA would even be pushing that a little bit. 12AX7 filament: 12.6V 0.15A for 1.89W filament power, expect lower cathode emission. 90 mA peak is pushing that. 8W from 8K p-p, not even considering output transformer efficiency, needs almost 90mA peak. 6SN7 dissipation spec: 5W per plate, but 7.5 w total when both plates are hot. 12AX7 dissipation spec: 1.2W per plate. Whoa. Maybe this figure is low, anticipating a shield around the tube that would hold in the heat. Plate Dissipation 8W RMS, that's 16W peak. 8K p-p, that's 2K plate to B+, that means: 16W peak, 2K, 178V peak to zero 178V peak, 2K, 89.4mA peak per plate. 178 V peak, plate at least +250V, maybe +300V, to give that much swing. 250V plate and -2.2V grid bias would have 1mA resting currrent per plate, for 0.25W resting dissipation per plate. Minimum instantaneous plate voltage at the audio peak would be +72V. 300V plate and -2.6V grid bias would have 1mA resting current per plate, for 0.3W resting dissipation per plate, probably OK. Minimum instantaneous plate voltage at the audio peak would be 122V, so dissipation would be significantly higher with audio than it would be with 250V at -2.2V bias, but the 90mA peak plate current would be easier to achieve. 8W out, class B, at this low voltage means at least 5W dissipation, 2.5W per plate, for a continuous sine wave at full power. That's pushing it. Maybe it's OK if the 12AX7 was rated very conservatively, or if the duty cycle is low enough. Zero bias? 250V plate, zero bias, 7mA resting current, 1.75W per plate resting dissipation per plate. 300V plate, zero bias, 9.2mA resting current, 2.8W per plate resting dissipation. Can the 1.2W per plate dissipation spec be this conservative? Maybe with a high grid leak resistance it would self-bias a bit, and work. Bacon, WA3WDR - Original Message - From: "Patrick Jankowiak" <[EMAIL PROTECTED]> To: Sent: Saturday, October 01, 2005 10:15 AM Subject: Re: [AMRadio] GG 813 Linear in GE Ham News -12AT7 12AX7 > don't laugh too hard, In the ARRL handbook it claims 8 watts audio from an > 12AX7 in zero bias class B push pull into 8000 ohms. I have never > understood that one, if you look at the currents stated in the book, they > seem pretty high for the tube. > > PJ > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami >
Re: [AMRadio] GG 813 Linear in GE Ham News
John E. Coleman (ARS WA5BXO) wrote: I have an SB200 linear and on AM it is equivalent to a DX100. I increased the bias on it so to the point just beyond cutoff for AM so that it requires a little more to drive and it reaches negative 100% modulation slightly before the driver does. But this seemed to help the modulation linearity and efficiency just a little. I really use this position mostly for CW drive to the push pull 250th rig. But I have occasionally put it on the air and switched the driver to AM. John, WA5BXO I've never heard your rig in that configuration, but I -have- heard it on the air, recently. Twice in as many days, actually! Can't say that I've heard a rig sound better than the 'peanut whistle' from Willis, TX ;-) Looking forward to climing the 100' tower with Larry/WD5CFJ this week, John. -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] GG 813 Linear in GE Ham News -12AT7 12AX7
Patrick Jankowiak wrote: don't laugh too hard, In the ARRL handbook it claims 8 watts audio from an 12AX7 in zero bias class B push pull into 8000 ohms. I have never understood that one, if you look at the currents stated in the book, they seem pretty high for the tube. PJ Oh, I don't know... 250Ep into 8kOhms is 0.03125A (around 30mA) 250Ep * 30mA Ip = 7.8125W --- -Geoff/W5OMR
Re: [AMRadio] GG 813 Linear in GE Ham News -12AT7 12AX7
well. there are several dozen examples of this in the mobile handbooksCQ magazine and QST,both of the CQ books and all five of the ARRL's. It was done to get lots of audio, very low resting current, ditto 1635, a special 6N7 with zero resting current gives 14 watts sine wave RMS, can be made to modulate 50 watts with reasonable tube life. Remember, speech is 20-25 percent of peak when viewed as average. That is why 3 kw Alphas only have 1kw CCS supplies!.On the 12AX7, my mobile used this for years and no tube ever failed. Lotsa good audio!.. Mike - Original Message - From: "Patrick Jankowiak" <[EMAIL PROTECTED]> To: Sent: Saturday, October 01, 2005 10:15 AM Subject: Re: [AMRadio] GG 813 Linear in GE Ham News -12AT7 12AX7 > don't laugh too hard, In the ARRL handbook it claims 8 watts audio from an > 12AX7 in zero bias class B push pull into 8000 ohms. I have never > understood that one, if you look at the currents stated in the book, they > seem pretty high for the tube. > > PJ > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami >
RE: [AMRadio] GG 813 Linear in GE Ham News
I have an SB200 linear and on AM it is equivalent to a DX100. I increased the bias on it so to the point just beyond cutoff for AM so that it requires a little more to drive and it reaches negative 100% modulation slightly before the driver does. But this seemed to help the modulation linearity and efficiency just a little. I really use this position mostly for CW drive to the push pull 250th rig. But I have occasionally put it on the air and switched the driver to AM. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim candela Sent: Friday, September 30, 2005 6:47 PM To: Discussion of AM Radio Subject: RE: [AMRadio] GG 813 Linear in GE Ham News Don, So your saying that 4 X 811's at maximum ratings in AM Linear mode are nearly equivalent to 3 6146's class C plate modulated, i.e. a Johnson Valiant? :-) Years ago I bought a book from an ad in the old AM Press Exchange about AM, and there was a detailed explanation of class C plate modulated versus AM linear operation with the same tubes, and it clearly showed the differences. I need to go find that book again... Jim -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Donald Chester Sent: Friday, September 30, 2005 1:58 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] GG 813 Linear in GE Ham News >.hey don,what are your thoughts of am transmission >with 4 811s?..i'm looking to get more output on 160 >am.. In linear service, the maximum carrier output would be half the plate dissipation. The pd of the 811A is 65 watts. So for a quad, the maxumum safe carrier output would be 130 watts. In grounded grid service, some of drive power will feed through, so you might add 10% to that, bringing the carrier output power to 143 watts give or take a few. With the pair of 813's you would add some feedthrough power to the 125 watts. I would say more like 12.5 watts, to bring the total to 137.5 watts. Most g-g linears take about 10% of the output power to drive them. Don K4KYV __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.9/115 - Release Date: 9/29/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.9/115 - Release Date: 9/29/2005 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami
Re: [AMRadio] GG 813 Linear in GE Ham News -12AT7 12AX7
don't laugh too hard, In the ARRL handbook it claims 8 watts audio from an 12AX7 in zero bias class B push pull into 8000 ohms. I have never understood that one, if you look at the currents stated in the book, they seem pretty high for the tube. PJ
Re: [AMRadio] GG 813 Linear in GE Ham News
The figures are about right, half the rated dissipation is about what carrier level should be. I used to run a pair of 813's in parallel, zero bias GG on AM. carrier: 2200 volts 150 mA 90W out 240W dissipation and the tubes ran with color allright! "single tone" 2000 volts 300mA 360 W out 260W dissipation (brighter color) something was never quite righ with the efficiency in that amplifier, but it was running close to the max. frequency for the 813 and they are not too efficient there. A big fan on the bulb works wonders for the 813. PJ
Re: [AMRadio] GG 813 Linear in GE Ham News
In a message dated 9/30/05 8:28:14 PM, [EMAIL PROTECTED] writes: > ..ok don,then what if went with 4 572b's instead? they > have a higher pd i believe..tim..sk.. > How about 100 X 12AT7s? At 5 W dissipation per tube (Sylvania tec manual) should be good for 250 watts of carrier. Would need a 300 vdc @ 2.5 amp power supply. Input and output matching circuits might be a bit of a challenge, though Seriously, why not go with something like a 4-400 triode connected. Or maybe a couple in parallel for some serious power. These jugs seem to be readily available at reasonable prices. Had no problem accumulating a lifetime supply for my T368. Dennis D. W7QHO Glendale, CA
RE: [AMRadio] GG 813 Linear in GE Ham News
..ok don,then what if went with 4 572b's instead? they have a higher pd i believe..tim..sk.. --- Jim candela <[EMAIL PROTECTED]> wrote: > Don, > > So your saying that 4 X 811's at maximum ratings > in AM Linear mode are > nearly equivalent to 3 6146's class C plate > modulated, i.e. a Johnson > Valiant? :-) > Years ago I bought a book from an ad in the old AM > Press Exchange about AM, > and there was a detailed explanation of class C > plate modulated versus AM > linear operation with the same tubes, and it clearly > showed the differences. > I need to go find that book again... > > Jim > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of > Donald Chester > Sent: Friday, September 30, 2005 1:58 PM > To: amradio@mailman.qth.net > Subject: Re: [AMRadio] GG 813 Linear in GE Ham News > > > > > >.hey don,what are your thoughts of am transmission > >with 4 811s?..i'm looking to get more output on 160 > >am.. > > In linear service, the maximum carrier output would > be half the plate > dissipation. The pd of the 811A is 65 watts. So > for a quad, the maxumum > safe carrier output would be 130 watts. > > In grounded grid service, some of drive power will > feed through, so you > might add 10% to that, bringing the carrier output > power to 143 watts give > or take a few. > > With the pair of 813's you would add some > feedthrough power to the 125 > watts. I would say more like 12.5 watts, to bring > the total to 137.5 watts. > > Most g-g linears take about 10% of the output power > to drive them. > > Don K4KYV > > > __ > AMRadio mailing list > Home: > http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami > -- > No virus found in this incoming message. > Checked by AVG Anti-Virus. > Version: 7.0.344 / Virus Database: 267.11.9/115 - > Release Date: 9/29/2005 > > -- > No virus found in this outgoing message. > Checked by AVG Anti-Virus. > Version: 7.0.344 / Virus Database: 267.11.9/115 - > Release Date: 9/29/2005 > > __ > AMRadio mailing list > Home: > http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami > __ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com
RE: [AMRadio] GG 813 Linear in GE Ham News
Don, So your saying that 4 X 811's at maximum ratings in AM Linear mode are nearly equivalent to 3 6146's class C plate modulated, i.e. a Johnson Valiant? :-) Years ago I bought a book from an ad in the old AM Press Exchange about AM, and there was a detailed explanation of class C plate modulated versus AM linear operation with the same tubes, and it clearly showed the differences. I need to go find that book again... Jim -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Donald Chester Sent: Friday, September 30, 2005 1:58 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] GG 813 Linear in GE Ham News >.hey don,what are your thoughts of am transmission >with 4 811s?..i'm looking to get more output on 160 >am.. In linear service, the maximum carrier output would be half the plate dissipation. The pd of the 811A is 65 watts. So for a quad, the maxumum safe carrier output would be 130 watts. In grounded grid service, some of drive power will feed through, so you might add 10% to that, bringing the carrier output power to 143 watts give or take a few. With the pair of 813's you would add some feedthrough power to the 125 watts. I would say more like 12.5 watts, to bring the total to 137.5 watts. Most g-g linears take about 10% of the output power to drive them. Don K4KYV __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.9/115 - Release Date: 9/29/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.9/115 - Release Date: 9/29/2005
Re: [AMRadio] GG 813 Linear in GE Ham News
How about using 6 811's. I built a gg 160m only amp like this back in the early eighties. Still works great today. And one of the cool things about using the six tubes in gg, is the fact that the input impedance is 50 ohms. No imput matching network required if your using a solid state exciter. George KE4HJ Donald Chester wrote: .hey don,what are your thoughts of am transmission with 4 811s?..i'm looking to get more output on 160 am.. In linear service, the maximum carrier output would be half the plate dissipation. The pd of the 811A is 65 watts. So for a quad, the maxumum safe carrier output would be 130 watts. In grounded grid service, some of drive power will feed through, so you might add 10% to that, bringing the carrier output power to 143 watts give or take a few. With the pair of 813's you would add some feedthrough power to the 125 watts. I would say more like 12.5 watts, to bring the total to 137.5 watts. Most g-g linears take about 10% of the output power to drive them. Don K4KYV __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami
Re: [AMRadio] GG 813 Linear in GE Ham News
.hey don,what are your thoughts of am transmission with 4 811s?..i'm looking to get more output on 160 am.. In linear service, the maximum carrier output would be half the plate dissipation. The pd of the 811A is 65 watts. So for a quad, the maxumum safe carrier output would be 130 watts. In grounded grid service, some of drive power will feed through, so you might add 10% to that, bringing the carrier output power to 143 watts give or take a few. With the pair of 813's you would add some feedthrough power to the 125 watts. I would say more like 12.5 watts, to bring the total to 137.5 watts. Most g-g linears take about 10% of the output power to drive them. Don K4KYV
RE: [AMRadio] GG 813 Linear in GE Ham News
Don, That was a good analysis. I'll add a little twist here. By adding a little carrier control, like a DX-60 driver, the whole situation changes allowing higher PEP output with lower unmodulated Plate dissipation of the RF linear amp tubes.. Of course now we're compromising AM to appease the linear, and making the receiving station's S-meter pump with the transmitters voice peak level. Back to what you were saying about the 813, at 125 watts Pd CCS, and 125 watts ICAS Pd. Hold an 813 next to a 572B which is rated at 160 watts (ICAS?). To me the 813 is a beefier tube. Maybe the rating disparity has to do more with marketing than engineering where the 572B will have lower lifetime in service at higher ratings, or maybe they assume SSB where the tube only sees brief full power tune ups, and then SSB voice transmission. Regards, Jim Candela WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Donald Chester Sent: Thursday, September 29, 2005 2:59 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] GG 813 Linear in GE Ham News >>>A pair of 813s in GG are only good for 150 watts carrier out on AM. Actually, that figure is optimistic. And p.e.p. has nothing to do with it. The limiting factor is plate dissipation of the tubes. A properly adjusted AM linear runs about 33% carrier efficiency if it is adjusted for modulation capability of 100% That means, with no modulation, about one third the DC input is converted to rf. The other two thirds of the input power is radiated as heat. So the maximum plate dissipation is twice the carrier output. Conversely, the maximum carrier output power is one-half the rated plate dissipation of the tubes. The 813 is rated by RCA at 125 watts plate dissipation. (I believe that is the ICAS rating; the CCS rating would be even less). So a pair of 813's has a total plate dissipation rating of 250 watts. Therefore, the maximum carrier output in AM linear service would be 125 watts, not 150. They would probably run at 150 watts, but if you maintained 100% modulation capability, they would run hot, and the tube life would be shortened. At the maximum rated output of 125 watts carrier, the DC input is 375 watts. Of that power, 125 watts is delivered as rf output, and the other 250 watts is radiated as heat from the plates of the tubes. Under modulation, the tubes will cool down a little. With a properly adjusted amplifier, the DC input will not change as modulation is applied. Theoretically, the plate meter will remain perfectly still. But as modulation is applied to the signal, the rf output increases because you now have carrier power plus sideband power. If the DC input remains the same, that extra power has to come from somewhere, so what happens is that less power is dissipated in the tubes and more power is delivered as output. But since in AM voice sevice, there are substantial periods without modulation, the amplifier must be designed to safely run for extended periods in the unmodulated carrier mode. You could increase the p.e.p. output of the tubes by increasing plate voltage. It would work with SSB because of the light duty cycle of a suppressed carrier signal. Depending on the peak-to-average ratio of the voice characteristic, you might be able to substantially increase the p.e.p. output without exceeding the plate dissipation rating of the tubes. But with AM, increasing the p.e.p. output necessarily means increasing the plate dissipation of the tubes, which are already running at max @ 125 watts output. In the AM mode, the transmitter would be capable of only 500 watts p.e.p. Don k4kyv __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.8/114 - Release Date: 9/28/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.9/115 - Release Date: 9/29/2005
RE: [AMRadio] GG 813 Linear in GE Ham News
Here is an email trail from this reflector from November of last year that seems to be on topic: Gary, I like your analysis on the topic. Brian may be looking for hard data to back up the theoretical. I recently finished a single EL-34 (6CA7) Class AB2 RF linear amplifier in a Central electronics 20a. In my case I got only 20% efficiency on AM! I am going to present some data achieved on 80 meters here: Condition Maximum CW output: Power Output 40 watts Plate Voltage 615 v Screen voltage 300 v Screen current 30ma Cathode current 178 ma DC plate input power 91 watts Plate circuit efficiency 44% Plate dissipation 51 watts* Condition ready for AM modulation: Power Output 8 watts Plate Voltage 636 v Screen voltage 309 v Screen current 11 ma Cathode current 74 ma DC plate input power 40 watts Plate circuit efficiency 20% Plate dissipation 32 watts* Keep in mind that the CCS EL-34 plate dissipation rating is 25 watts. With forced air cooling, and brief full power tune ups, the Russian tube behaves pretty well considering the abuse I am giving it. The tube plate does show some red however on AM, and even more at maximum CW output. This example of an overloaded EL-34 is somewhat similar to the overloaded 811 in earlier examples in this email thread. I had circuit variations that offered increased power and efficiency at the expense of linearity. With this tube, getting good linearity on AM (seen on trapezoid pattern on scope) resulted in a pretty hot tube. I even added feedback where I rectified the RF output, obtained audio and sent that back to the speech amp for audio inverse feedback. That technique works extremely well. * This includes losses in the output coupling circuit; the Lucite strips securing the tank coil tend to soften and droop at 50 watts RF output when on 160 meters. Maybe I actually am getting closer to 30% PLATE efficiency on AM. Regards, Jim Candela WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Gary Schafer Sent: Monday, November 22, 2004 9:23 PM To: [EMAIL PROTECTED]; Discussion of AM Radio Subject: Re: [AMRadio] AM Usage with Linear AMPS Brian, What he is saying is: you need to have the 811A tuned up at 200 watts output on cw or pep for a 50 watt carrier out. (pep is 4 times carrier) When you tune up you tune it for max output at the 200 watt level with full drive. At that tune setting the tube will be around 60% efficient. Normal ssb or cw operation tune-up. input power will be 333 watts. The tube will be dissipating 133 watts in heat at full carrier. You then reduce the drive until you have 50 watts out (1/4 the carrier of full output). You can not retune at this point or it will not handle the peak envelope power of 4 times carrier. At 50 watts out the efficiency drops to around 30%. So that means to get the 50 watts out the tube has to be running around 150 watts input. 150 watts minus the 50 watts output leaves 100 watts to dissipate in heat in the plate as long as the carrier is on. It doesn't get any better either. With modulation the dissipation does not decrease even though the efficiency increases at the peak power levels. The carrier power is still there 100% of the time at 30% efficiency. The audio is in the form of separate side bands that is additional power that the tube has to handle. I guarantee you that an 811A will run with a red plate under these conditions. If it is not red then it is not tuned up properly for this mode of operation at the 50 watt carrier out level. 73 Gary K4FMX Brian Carling wrote: > On 22 Nov 2004 at 20:23, [EMAIL PROTECTED] wrote: > > >>Going to shorten it's life considerably. > > > Theoretically maybe. Have you tried it. How can you know > for sure? Theory says a bumble bee can't fly. My 811A tubes > never burned up. > > Where did you get your 30% number from? Who transmits > their AM with carrier only!? I can't see how a 50 watt carrier input > will cause an 811A to DISSIPATE 100 watts! > Where are you getting the additional 50? > > >>To properly adjust a linear amp for AM it is necessary to tune the thing up for the peak power >>level, i.e., 200 watts for a 50W carrier. The linear will be about 60% efficient at this output level. >>Then WITHOUT CHANGING THE TUNING adjust the output from the AM exciter to provide for >>50W out of the linear with no modulation. The problem here is that the linear will now only be >>running about 30% efficiency under carrier-only conditions and the 811 would be dissipating >>something like 100+ watts. The 811A, of course, is only rated at 65 watts. >> >>Dennis D. W7QHO >>Glendale, CA > > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.9/115 - Release Date: 9/29/2005
Re: [AMRadio] GG 813 Linear in GE Ham News
In this case that is near correct. There is some feed through power also present. But the limiting factor is not always one half total plate dissipation. If the tubes were run in class A rather than B then output would be limited to much less than half the plate dissipation. At 33% efficiency in class A at full PEP the efficiency for the carrier would be 16.5%. Carrier power would then be limited to 41.25 watts plus a little feed through power. That's with an input of 250 watts. 73 Gary K4FMX Mike Dorworth,K4XM wrote: Actually, only one half of plate dissipation. The ICAS dissipation for a single 813 is 125 watts, CCS is 100 watts.. This is the maximum carrier for reasonable tube life. Efficiency is low without modulation., increases during modulation. Limiting factor is one half total dissipation.Sorry but the facts are so. Mike - Original Message - From: "W5OMR/Geoff" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, September 29, 2005 6:03 AM Subject: Re: [AMRadio] GG 813 Linear in GE Ham News Gary Schafer wrote: A pair of 813s in GG are only good for 150 watts carrier out on AM. 73 Gary K4FMX I'm not trying to start anything here, Gary, but that statement seems to be in stark contrast to what you said, yesterday... With an AM linear the efficiency at carrier must be / will be exactly one half what it is at PEP. Provided it is tuned properly. 73 Gary K4FMX What would the efficiency be of an AM Linear at carrier. (or maybe I'm not reading this correctly, because I've yet to have coffee this morning, and I -know- I probably should'n't be posting messages in this state... ;-)) -- 73 = Best Regards, -Geoff/W5OMR __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami
Re: [AMRadio] GG 813 Linear in GE Ham News
Actually, only one half of plate dissipation. The ICAS dissipation for a single 813 is 125 watts, CCS is 100 watts.. This is the maximum carrier for reasonable tube life. Efficiency is low without modulation., increases during modulation. Limiting factor is one half total dissipation.Sorry but the facts are so. Mike - Original Message - From: "W5OMR/Geoff" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, September 29, 2005 6:03 AM Subject: Re: [AMRadio] GG 813 Linear in GE Ham News > Gary Schafer wrote: > > > A pair of 813s in GG are only good for 150 watts carrier out on AM. > > > > 73 > > Gary K4FMX > > > > I'm not trying to start anything here, Gary, but that statement seems to > be in stark contrast to what you said, yesterday... > > > With an AM linear the efficiency at carrier must be / will be exactly > > one half what it is at PEP. Provided it is tuned properly. > > > > 73 > > Gary K4FMX > > > What would the efficiency be of an AM Linear at carrier. > > (or maybe I'm not reading this correctly, because I've yet to have > coffee this morning, and I -know- I probably should'n't be posting > messages in this state... ;-)) > > -- > 73 = Best Regards, > -Geoff/W5OMR > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami >
Re: [AMRadio] GG 813 Linear in GE Ham News
.hey don,what are your thoughts of am transmission with 4 811s?..i'm looking to get more output on 160 am.. //tim...sk.. --- Donald Chester <[EMAIL PROTECTED]> wrote: > > > >>>A pair of 813s in GG are only good for 150 watts > carrier out on AM. > > > Actually, that figure is optimistic. And p.e.p. has > nothing to do with it. > The limiting factor is plate dissipation of the > tubes. > > A properly adjusted AM linear runs about 33% carrier > efficiency if it is > adjusted for modulation capability of 100% That > means, with no modulation, > about one third the DC input is converted to rf. > The other two thirds of > the input power is radiated as heat. So the maximum > plate dissipation is > twice the carrier output. Conversely, the maximum > carrier output power is > one-half the rated plate dissipation of the tubes. > > The 813 is rated by RCA at 125 watts plate > dissipation. (I believe that is > the ICAS rating; the CCS rating would be even less). > So a pair of 813's has > a total plate dissipation rating of 250 watts. > Therefore, the maximum > carrier output in AM linear service would be 125 > watts, not 150. They would > probably run at 150 watts, but if you maintained > 100% modulation capability, > they would run hot, and the tube life would be > shortened. > > At the maximum rated output of 125 watts carrier, > the DC input is 375 watts. > Of that power, 125 watts is delivered as rf > output, and the other 250 > watts is radiated as heat from the plates of the > tubes. > > Under modulation, the tubes will cool down a little. > With a properly > adjusted amplifier, the DC input will not change as > modulation is applied. > Theoretically, the plate meter will remain perfectly > still. But as > modulation is applied to the signal, the rf output > increases because you now > have carrier power plus sideband power. If the DC > input remains the same, > that extra power has to come from somewhere, so what > happens is that less > power is dissipated in the tubes and more power is > delivered as output. > > But since in AM voice sevice, there are substantial > periods without > modulation, the amplifier must be designed to safely > run for extended > periods in the unmodulated carrier mode. > > You could increase the p.e.p. output of the tubes by > increasing plate > voltage. It would work with SSB because of the > light duty cycle of a > suppressed carrier signal. Depending on the > peak-to-average ratio of the > voice characteristic, you might be able to > substantially increase the p.e.p. > output without exceeding the plate dissipation > rating of the tubes. But > with AM, increasing the p.e.p. output necessarily > means increasing the plate > dissipation of the tubes, which are already running > at max @ 125 watts > output. In the AM mode, the transmitter would be > capable of only 500 watts > p.e.p. > > Don k4kyv > > > __ > AMRadio mailing list > Home: > http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami > __ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com
Re: [AMRadio] GG 813 Linear in GE Ham News
A pair of 813s in GG are only good for 150 watts carrier out on AM. Actually, that figure is optimistic. And p.e.p. has nothing to do with it. The limiting factor is plate dissipation of the tubes. A properly adjusted AM linear runs about 33% carrier efficiency if it is adjusted for modulation capability of 100% That means, with no modulation, about one third the DC input is converted to rf. The other two thirds of the input power is radiated as heat. So the maximum plate dissipation is twice the carrier output. Conversely, the maximum carrier output power is one-half the rated plate dissipation of the tubes. The 813 is rated by RCA at 125 watts plate dissipation. (I believe that is the ICAS rating; the CCS rating would be even less). So a pair of 813's has a total plate dissipation rating of 250 watts. Therefore, the maximum carrier output in AM linear service would be 125 watts, not 150. They would probably run at 150 watts, but if you maintained 100% modulation capability, they would run hot, and the tube life would be shortened. At the maximum rated output of 125 watts carrier, the DC input is 375 watts. Of that power, 125 watts is delivered as rf output, and the other 250 watts is radiated as heat from the plates of the tubes. Under modulation, the tubes will cool down a little. With a properly adjusted amplifier, the DC input will not change as modulation is applied. Theoretically, the plate meter will remain perfectly still. But as modulation is applied to the signal, the rf output increases because you now have carrier power plus sideband power. If the DC input remains the same, that extra power has to come from somewhere, so what happens is that less power is dissipated in the tubes and more power is delivered as output. But since in AM voice sevice, there are substantial periods without modulation, the amplifier must be designed to safely run for extended periods in the unmodulated carrier mode. You could increase the p.e.p. output of the tubes by increasing plate voltage. It would work with SSB because of the light duty cycle of a suppressed carrier signal. Depending on the peak-to-average ratio of the voice characteristic, you might be able to substantially increase the p.e.p. output without exceeding the plate dissipation rating of the tubes. But with AM, increasing the p.e.p. output necessarily means increasing the plate dissipation of the tubes, which are already running at max @ 125 watts output. In the AM mode, the transmitter would be capable of only 500 watts p.e.p. Don k4kyv
Re: [AMRadio] GG 813 Linear in GE Ham News
Bill i do not have that issues of ham news would like a copy also. thanks 73 Tony QBE ZUT DE WA4JQS ANTHONY W. (Tony) DePrato WA4JQS EXTRA - HEAVY Since 1962 CQ DX HALL OF FAME # 35 A1-OP FISTS # 10573 South Sandwich Island Dxpedition Group CALLS HELD: WA4JQS/ZS1, WA4JQS/KC4, WA4JQS/4K1 ZD8JQS, V31SS, VP8BZL, VP8SSI, 3Y0PI
Re: [AMRadio] GG 813 Linear in GE Ham News
You got it Geoff!! :>) 73 Gary K4FMX W5OMR/Geoff wrote: Gary Schafer wrote: See? I -knew- I was getting muddled again. (~sigh~) Gary, let me apologize for not understanding your statements, but I'll stand by what I said to be wholly true. I've been corrected, and it's a true statement. Read below" Gary wrote: It does not matter what type of signal is modulating the signal when the linear amp is involved. Whether it is a sine wave or speech or anything else. The PEP rule still applies for 100% modulation! You can not exceed 100% positive peak modulation if the carrier is set at any level greater than 1/4 the PEP output capability of the amplifier. Unless you want to operate it in a non linear mode. Geoff Wrote: <>>I Disagree with that. Gary's statement is true. He is speaking of the PEP max output capability of the AMP. If the PEP maxoutput of the amp is 1000 watts then regardless of the symmetry of the audio, <>250 watts is the max carrier it should run on output. If asymmetrical then you would need to reduce the carrier to maybe 100 watts output. At 250 watts carrier output the amp would reach saturation before 100% modulation in any case. Sorry, sir. -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] GG 813 Linear in GE Ham News
Gary Schafer wrote: See? I -knew- I was getting muddled again. (~sigh~) Gary, let me apologize for not understanding your statements, but I'll stand by what I said to be wholly true. I've been corrected, and it's a true statement. Read below" Gary wrote: It does not matter what type of signal is modulating the signal when the linear amp is involved. Whether it is a sine wave or speech or anything else. The PEP rule still applies for 100% modulation! You can not exceed 100% positive peak modulation if the carrier is set at any level greater than 1/4 the PEP output capability of the amplifier. Unless you want to operate it in a non linear mode. Geoff Wrote: <>>I Disagree with that. Gary's statement is true. He is speaking of the PEP max output capability of the AMP. If the PEP maxoutput of the amp is 1000 watts then regardless of the symmetry of the audio, <>250 watts is the max carrier it should run on output. If asymmetrical then you would need to reduce the carrier to maybe 100 watts output. At 250 watts carrier output the amp would reach saturation before 100% modulation in any case. Sorry, sir. -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] GG 813 Linear in GE Ham News
Gary Schafer wrote: Geoff, I am ONLY talking about a linear amplifier here. The drive signal is already modulated. If you are modulating the final stage these efficiency rules discussed here do not apply. Unless you would be talking about grid modulation and then they "do apply". Yup - you're right ;-) I'm getting muddled, here, between plate-modulating a grounded grid amp, and using the grounded grid amp, after a low-level AM source. Big difference. Sorry for the misunderstanding. It does not matter what type of signal is modulating the signal when the linear amp is involved. Whether it is a sine wave or speech or anything else. The PEP rule still applies for 100% modulation! You can not exceed 100% positive peak modulation if the carrier is set at any level greater than 1/4 the PEP output capability of the amplifier. Unless you want to operate it in a non linear mode. I Disagree with that. K4KYV said: "Overmodulation" is defined not necessarily as exceeding 100%, but exceeding the MODULATION CAPABILITY of the transmitter. As soon as the final amplifier plate voltage goes past zero, you have exceeded the modulation capability of the transmitter, whether there is still rf output or not. That being said, if I were to take a small rig, like a Ranger, or an AF-67/8, modify it so that there was plenty of audio available to faithfully reproduce my peaked voice, (natural asymmetry) the positive peaks -will- reach beyond the 2:1 level, that one would observe when looking at an AM carrier (on a scope) modulated to 100% with a sine-wave. Here's an example... http://w5omr.shacknet.nu:81/~w5omr/pictures/2005-08-08/000_0049.MOV it's a short 1meg video file The text spoken into the mic is "hell test, one, two threee, four." Note that the unmodulate carrier occupies 2 squares (centimeters) on the scope. The positive peaks are reaching 8 centimeters, pk-to-pk, while the negative cycle comes right down to the carrier. That's a positive to negative peak ratio of 4:1. Let's assume that's a 100w carrier. 4x the carrier for PEP would mean 400w PEP output. That's with a standard 2:1 ratio. Since the voltage and current are both being doubled, how much power, in PEP do you think a 4:1 ratio is? (hint: it ain't 800w PEP) With this in mind, if I attempt to use this 100w rig with a linear amplifier and 8:1 Symmetry Ratio, I'd have to have at -least- an amplifier with a pair of 4-1000's in it, to properly handle the maximum PEP power out, with a nominal 100w of drive. The whole purpose of this part of the discussion, Gary, is to 'bust' the mythical "375w AM legal limit output carrier power" nonsense, and to alert and advise people that while PEP = 4x Carrier leve for 100% modulation is true for a sinewave, it ain't true for the human voice. Especially the peakedness of the typical male-patterned voice. I'm not saying that you shouldn't run your AM rig to 500w DC Input (which, for a class C amp at 75% is around 375w) or at whatever power level you feel comforable with(*), but just be aware of the PEP 'Federal Law' that is place. PEP = 4x the AM Carrier at 100% modulation is true, -ONLY- if you're using a sine-wave to modlulate the carrier. (Operating your AM Rig without a 'Scope, is like driving your car at night without headlights! -Don Chester/K4KYV Ex. Editor: AM/Px) -- 73 = Best Regards, -Geoff/W5OMR (* = Remember in 1990, before the 1991 ruling that made this a federal law, when the phrase "When AM kW's are outlawed, then only Outlaws will be running AM kW's" was popular?)
Re: [AMRadio] GG 813 Linear in GE Ham News
W5OMR/Geoff wrote: Hi Geoff, Yes both statements are true. Remember that the PEP is 4 times the carrier power with a 100% modulated AM signal. if it's modulated with a sine-wave, that's a true statement. A pair of 813s are good for about 600 watts PEP output. So that limits carrier power to 150 watts if 100% modulation is used. I understand that, but in a grounded grid arrangement, as it's already been said here, there's the exciter drive power that's added to the signal. So, in order for there to be 100% modulation, you must modulate the exciter, as well. The "efficiency at carrier" that I was referring to is the efficiency of the amplifier at the power level that the carrier runs when any amplifier is set up for AM operation. Like the 813s, 600 watts PEP out requires that the carrier be operated at 150 watts output. Thereabouts. Again, if you're modulating it with a sine-wave, then it holds true that 100% modulation is 4x the carrier output. However, we don't speak in sinewaves, as John/WA5BXO, Don/K4KYV and Bob(Bacon)/WA3WDR have so eloquently stated in http://w5omr.shacknet.nu:81/~wa5bxo/asyam/Amplitude%20Modulation.htm If the amplifier has say 60% efficiency at the full PEP level then at 1/4 the power output the efficiency will be 1/2 of what it was at full power or 30% in this case. This is not only true for AM operation but for SSB operation as well. As long as the amplifier is to remain linear this efficiency ratio must exist. (see Orr's radio handbook. see "efficiency modulation") If that efficiency ratio is not maintained then the amplifier is not operating linearly. If you readjust the loading at carrier level to increase the power then it will no longer be linear when the modulation is applied. Which, to me, would be another good reason why you shouldn't plate-modulate a grounded-grid (aka 'linear') amplifier. -- 73 = Best Regards, -Geoff/W5OMR Geoff, I am ONLY talking about a linear amplifier here. The drive signal is already modulated. If you are modulating the final stage these efficiency rules discussed here do not apply. Unless you would be talking about grid modulation and then they "do apply". It does not matter what type of signal is modulating the signal when the linear amp is involved. Whether it is a sine wave or speech or anything else. The PEP rule still applies for 100% modulation! You can not exceed 100% positive peak modulation if the carrier is set at any level greater than 1/4 the PEP output capability of the amplifier. Unless you want to operate it in a non linear mode. 73 Gary K4FMX
Re: [AMRadio] GG 813 Linear in GE Ham News
Hi Jim, No magic in the 600L. If you run it at 100 watts carrier out then it has to be capable of 400 watts PEP output in order to be linear. That would be around 660 watts input. Assuming 60% efficiency in AB2 grid driven. At the 100 watt carrier level the efficiency would be around 30% so input power would be about 333 watts. Plate dissipation would be 233 watts! 813s will tolerate that for awhile. But I don't think the 600L will put out 400 watts PEP? At least not while being linear. You may be able to see that much out of it at tune up if driven hard but I would bet it gets driven closer to class C with that much power out. 73 Gary K4FMX Jim candela wrote: Gary, Yes your correct. That said a 813 has conservative Pd rating of 125 watts whereas tubes like the 572 which appear similar in plate area are rated for 160 watts Pd. The rule of thumb is for AM use is that the max carrier output is 1/2 the Pd of the tube(s) + feedthrough power (G-G circuit), so for two 813's we have (125 + 125)/2 + 25 (guess) = 150. This assumes an efficiency that is about 33% carrier alone, and 66% at 100% sine wave modulation. I bet we can get closer to 200 watts out for ICAS service and still have headroom for 100% modulation from a pair of 813's. Those tubes better be forced air cooled, and you better be talking without pause since the tubes will cool down with modulation (efficiency doubles at 100% sine wave modulation). This rule of thumb doesn't seem to apply to my Central electronics 600L linear which has a one 813 grid driven in AB2 mode. This amplifier can put out 100 watts carrier and modulate it fully to + 100%. This implies the tube is dumping 200 watts (no modulation) for 100 watts output. There is color in the tube for sure, but 200 watts? I don't think so. Maybe those broadband couplers in the patented 600L somehow boost the efficiency. I have never figured out why the 600L can do that. Jim WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Gary Schafer Sent: Wednesday, September 28, 2005 9:24 PM To: Discussion of AM Radio Subject: Re: [AMRadio] GG 813 Linear in GE Ham News A pair of 813s in GG are only good for 150 watts carrier out on AM. 73 Gary K4FMX [EMAIL PROTECTED] wrote: Hello All, The thread on final circuits has been great to follow especially with the mention of 813's. It is still a very cost effective tube and in good supply NOS since the audio crowd has yet to make much use of them. I have a copy of GE Ham News from Nov-Dec 1959 that features a "Kilowatt Grounded-Grid Linear Amplifier" to quote the cover. It uses a pair of 813s GG with a standard Pi Net output configuration 5 band switched 80 -10 mtrs. Looks real easy to build and with the exception of the B&W filament choke FC-15, I have most of the needed parts or can find them. The construction article is well documented and pictured. Is anyone is familiar with this amplifier or better yet knows of one being built? If 160 meters would be easy to extend to with more L & C where needed then it would work well for anyone with a good drive source. For those that do not have the Ham News Issue I can scan a copy and e-mail it. Thanks for any info, Bill KB3DKS/1 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.8/114 - Release Date: 9/28/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.8/114 - Release Date: 9/28/2005
Re: [AMRadio] GG 813 Linear in GE Ham News
Hi Geoff, Yes both statements are true. Remember that the PEP is 4 times the carrier power with a 100% modulated AM signal. if it's modulated with a sine-wave, that's a true statement. A pair of 813s are good for about 600 watts PEP output. So that limits carrier power to 150 watts if 100% modulation is used. I understand that, but in a grounded grid arrangement, as it's already been said here, there's the exciter drive power that's added to the signal. So, in order for there to be 100% modulation, you must modulate the exciter, as well. The "efficiency at carrier" that I was referring to is the efficiency of the amplifier at the power level that the carrier runs when any amplifier is set up for AM operation. Like the 813s, 600 watts PEP out requires that the carrier be operated at 150 watts output. Thereabouts. Again, if you're modulating it with a sine-wave, then it holds true that 100% modulation is 4x the carrier output. However, we don't speak in sinewaves, as John/WA5BXO, Don/K4KYV and Bob(Bacon)/WA3WDR have so eloquently stated in http://w5omr.shacknet.nu:81/~wa5bxo/asyam/Amplitude%20Modulation.htm If the amplifier has say 60% efficiency at the full PEP level then at 1/4 the power output the efficiency will be 1/2 of what it was at full power or 30% in this case. This is not only true for AM operation but for SSB operation as well. As long as the amplifier is to remain linear this efficiency ratio must exist. (see Orr's radio handbook. see "efficiency modulation") If that efficiency ratio is not maintained then the amplifier is not operating linearly. If you readjust the loading at carrier level to increase the power then it will no longer be linear when the modulation is applied. Which, to me, would be another good reason why you shouldn't plate-modulate a grounded-grid (aka 'linear') amplifier. -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] GG 813 Linear in GE Ham News
W5OMR/Geoff wrote: Gary Schafer wrote: A pair of 813s in GG are only good for 150 watts carrier out on AM. 73 Gary K4FMX I'm not trying to start anything here, Gary, but that statement seems to be in stark contrast to what you said, yesterday... With an AM linear the efficiency at carrier must be / will be exactly one half what it is at PEP. Provided it is tuned properly. 73 Gary K4FMX What would the efficiency be of an AM Linear at carrier. (or maybe I'm not reading this correctly, because I've yet to have coffee this morning, and I -know- I probably should'n't be posting messages in this state... ;-)) -- 73 = Best Regards, -Geoff/W5OMR Hi Geoff, Yes both statements are true. Remember that the PEP is 4 times the carrier power with a 100% modulated AM signal. A pair of 813s are good for about 600 watts PEP output. So that limits carrier power to 150 watts if 100% modulation is used. You can squeeze a little more power out of the 813s but they start to turn a little red. I have had a pair of 813s in grounded grid that I built about 30 years ago. Tough tubes. The "efficiency at carrier" that I was referring to is the efficiency of the amplifier at the power level that the carrier runs when any amplifier is set up for AM operation. Like the 813s, 600 watts PEP out requires that the carrier be operated at 150 watts output. If the amplifier has say 60% efficiency at the full PEP level then at 1/4 the power output the efficiency will be 1/2 of what it was at full power or 30% in this case. This is not only true for AM operation but for SSB operation as well. As long as the amplifier is to remain linear this efficiency ratio must exist. (see Orr's radio handbook. see "efficiency modulation") If that efficiency ratio is not maintained then the amplifier is not operating linearly. If you readjust the loading at carrier level to increase the power then it will no longer be linear when the modulation is applied. 73 Gary K4FMX
RE: [AMRadio] GG 813 Linear in GE Ham News
Gary, Yes your correct. That said a 813 has conservative Pd rating of 125 watts whereas tubes like the 572 which appear similar in plate area are rated for 160 watts Pd. The rule of thumb is for AM use is that the max carrier output is 1/2 the Pd of the tube(s) + feedthrough power (G-G circuit), so for two 813's we have (125 + 125)/2 + 25 (guess) = 150. This assumes an efficiency that is about 33% carrier alone, and 66% at 100% sine wave modulation. I bet we can get closer to 200 watts out for ICAS service and still have headroom for 100% modulation from a pair of 813's. Those tubes better be forced air cooled, and you better be talking without pause since the tubes will cool down with modulation (efficiency doubles at 100% sine wave modulation). This rule of thumb doesn't seem to apply to my Central electronics 600L linear which has a one 813 grid driven in AB2 mode. This amplifier can put out 100 watts carrier and modulate it fully to + 100%. This implies the tube is dumping 200 watts (no modulation) for 100 watts output. There is color in the tube for sure, but 200 watts? I don't think so. Maybe those broadband couplers in the patented 600L somehow boost the efficiency. I have never figured out why the 600L can do that. Jim WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Gary Schafer Sent: Wednesday, September 28, 2005 9:24 PM To: Discussion of AM Radio Subject: Re: [AMRadio] GG 813 Linear in GE Ham News A pair of 813s in GG are only good for 150 watts carrier out on AM. 73 Gary K4FMX [EMAIL PROTECTED] wrote: > Hello All, > > The thread on final circuits has been great to follow especially with the mention of 813's. > It is still a very cost effective tube and in good supply NOS since the audio crowd has yet to make much use of them. > I have a copy of GE Ham News from Nov-Dec 1959 that features a "Kilowatt Grounded-Grid Linear Amplifier" to quote the cover. > It uses a pair of 813s GG with a standard Pi Net output configuration 5 band switched 80 -10 mtrs. > Looks real easy to build and with the exception of the B&W filament choke FC-15, I have most of the needed parts or > can find them. The construction article is well documented and pictured. > Is anyone is familiar with this amplifier or better yet knows of one being built? If 160 meters would be easy to extend to with more L & C where needed then it would work well for anyone with a good drive source. > For those that do not have the Ham News Issue I can scan a copy and e-mail it. > > Thanks for any info, > Bill KB3DKS/1 > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami > > __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.8/114 - Release Date: 9/28/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.8/114 - Release Date: 9/28/2005
Re: [AMRadio] GG 813 Linear in GE Ham News
Gary Schafer wrote: A pair of 813s in GG are only good for 150 watts carrier out on AM. 73 Gary K4FMX I'm not trying to start anything here, Gary, but that statement seems to be in stark contrast to what you said, yesterday... With an AM linear the efficiency at carrier must be / will be exactly one half what it is at PEP. Provided it is tuned properly. 73 Gary K4FMX What would the efficiency be of an AM Linear at carrier. (or maybe I'm not reading this correctly, because I've yet to have coffee this morning, and I -know- I probably should'n't be posting messages in this state... ;-)) -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] GG 813 Linear in GE Ham News
Hello again, I have sent out a couple of scans of the Ham New Article via zip file attached with an e-mail. If they get through the spam filters and are usable then I will send the same to all who have requested a copy. I have filed this circuit in the to do folder along with other 813 final circuits that I am reviewing for a winter project. Thanks for your interest and comments! Enjoy! Bill KB3DKS/1
Re: [AMRadio] GG 813 Linear in GE Ham News
A pair of 813s in GG are only good for 150 watts carrier out on AM. 73 Gary K4FMX [EMAIL PROTECTED] wrote: Hello All, The thread on final circuits has been great to follow especially with the mention of 813's. It is still a very cost effective tube and in good supply NOS since the audio crowd has yet to make much use of them. I have a copy of GE Ham News from Nov-Dec 1959 that features a "Kilowatt Grounded-Grid Linear Amplifier" to quote the cover. It uses a pair of 813s GG with a standard Pi Net output configuration 5 band switched 80 -10 mtrs. Looks real easy to build and with the exception of the B&W filament choke FC-15, I have most of the needed parts or can find them. The construction article is well documented and pictured. Is anyone is familiar with this amplifier or better yet knows of one being built? If 160 meters would be easy to extend to with more L & C where needed then it would work well for anyone with a good drive source. For those that do not have the Ham News Issue I can scan a copy and e-mail it. Thanks for any info, Bill KB3DKS/1 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami
Re: [AMRadio] GG 813 Linear in GE Ham News
Barker & Williamson (B&W) built a Ground Grid Amplifier out of two 813s if you are interested. The manual is on BAMA. It is the LPA 1 73 Jim W5JO Rev. Don Sanders wrote: I would like a copy of the article. I have an amp in process-gathering parts now-was thinking of 4 572B's but 813 is good tube. Healthfully yours, DON W4BWS - Original Message - From: <[EMAIL PROTECTED]> To: Sent: Wednesday, September 28, 2005 12:25 AM Subject: [AMRadio] GG 813 Linear in GE Ham News Hello All, The thread on final circuits has been great to follow especially with the mention of 813's. It is still a very cost effective tube and in good supply NOS since the audio crowd has yet to make much use of them. I have a copy of GE Ham News from Nov-Dec 1959 that features a "Kilowatt Grounded-Grid Linear Amplifier" to quote the cover. It uses a pair of 813s GG with a standard Pi Net output configuration 5 band switched 80 -10 mtrs. Looks real easy to build and with the exception of the B&W filament choke FC-15, I have most of the needed parts or can find them. The construction article is well documented and pictured. Is anyone is familiar with this amplifier or better yet knows of one being built? If 160 meters would be easy to extend to with more L & C where needed then it would work well for anyone with a good drive source. For those that do not have the Ham News Issue I can scan a copy and e-mail it. Thanks for any info, Bill KB3DKS/1
Re: [AMRadio] GG 813 Linear in GE Ham News
I would like a copy of the article. I have an amp in process-gathering parts now-was thinking of 4 572B's but 813 is good tube. Healthfully yours, DON W4BWS - Original Message - From: <[EMAIL PROTECTED]> To: Sent: Wednesday, September 28, 2005 12:25 AM Subject: [AMRadio] GG 813 Linear in GE Ham News > Hello All, > > The thread on final circuits has been great to follow especially with the mention of 813's. > It is still a very cost effective tube and in good supply NOS since the audio crowd has yet to make much use of them. > I have a copy of GE Ham News from Nov-Dec 1959 that features a "Kilowatt Grounded-Grid Linear Amplifier" to quote the cover. > It uses a pair of 813s GG with a standard Pi Net output configuration 5 band switched 80 -10 mtrs. > Looks real easy to build and with the exception of the B&W filament choke FC-15, I have most of the needed parts or > can find them. The construction article is well documented and pictured. > Is anyone is familiar with this amplifier or better yet knows of one being built? If 160 meters would be easy to extend to with more L & C where needed then it would work well for anyone with a good drive source. > For those that do not have the Ham News Issue I can scan a copy and e-mail it. > > Thanks for any info, > Bill KB3DKS/1 > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami >
Re: [AMRadio] GG 813 Linear in GE Ham News
Bill I would love a copy of that particular GE Ham News! Thanks Ronnie -- Original Message --- From: [EMAIL PROTECTED] To: amradio@mailman.qth.net Sent: Wed, 28 Sep 2005 01:25:23 -0400 Subject: [AMRadio] GG 813 Linear in GE Ham News > Hello All, > > The thread on final circuits has been great to follow especially > with the mention of 813's. It is still a very cost effective tube > and in good supply NOS since the audio crowd has yet to make much > use of them. I have a copy of GE Ham News from Nov-Dec 1959 that > features a "Kilowatt Grounded-Grid Linear Amplifier" to quote the cover. > It uses a pair of 813s GG with a standard Pi Net output > configuration 5 band switched 80 -10 mtrs. Looks real easy to build > and with the exception of the B&W filament choke FC-15, I have most > of the needed parts or can find them. The construction article is > well documented and pictured. Is anyone is familiar with this > amplifier or better yet knows of one being built? If 160 meters > would be easy to extend to with more L & C where needed then it > would work well for anyone with a good drive source. For those that > do not have the Ham News Issue I can scan a copy and e-mail it. > > Thanks for any info, > Bill KB3DKS/1 > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami --- End of Original Message ---
