RE: [AMRadio] Re: Modulation transformer ID and repair
I always wanted to try feedback, from something like the mod monitor, or some sort of detector, and injecting into a low level audio stage Have not tried it yet tho... Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of John Coleman, ARS > WA5BXO > Sent: Monday, December 01, 2003 1:57 PM > To: amradio@mailman.qth.net > Subject: RE: [AMRadio] Re: Modulation transformer ID and repair > > > That's very true Bret. I got an idea about 20 years ago from RCA > and Gates BC XMTRS diagrams. They use direct coupled cathode > followers > to drive the grids of the 833s. Not a lot of trouble > considering the HV > transistors that we have today. The FETs and bipolar transistors have > better characteristics for that sort of thing than the 807s they used > back then. I would never go to a class B or AB2 grids with out my > transistor drivers. > See http://www.qsl.net/wa5bxo/driver1.html > > I have always wanted to try the inverse feed back circuits that > RCA and Gates used on the modulators. But I never have. I > once had the > schematic diagram of the Gates 1KW but lost it in the flood > of 94. I'm > sure there are a lot of ways to do it I just have never taken the time > to try. > > BTW I think your right. I have learned a lot more from stuff > that didn't work out quite right. > I think the most time consuming thing I ever did was to > neutralize a single triode using an inductor from plate to grid (in > series with a blocking cap of course. The inductor resonates > with the G > - P capacitance of the tube. Let me say "It Works very well, > but it is > not my first choice for construction mechanics, plus it has > to be tuned > every time you change frequency.) > > 73, > John, WA5BXO > > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski > Sent: Sunday, November 30, 2003 9:41 PM > To: amradio@mailman.qth.net > Subject: RE: [AMRadio] Re: Modulation transformer ID and repair > > The push pull parallel 100TH deck does take quite a bit of > driving power, with the losses, likely close to 20 watts, > which is what the UTC LS grid transformer is good for. > > That may be part of the problem, but class B triodes always > seem to sound less clean than a good AB1 amp. > > Brett > N2DTS > > > > > > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio
RE: [AMRadio] Re: Modulation transformer ID and repair
That's very true Bret. I got an idea about 20 years ago from RCA and Gates BC XMTRS diagrams. They use direct coupled cathode followers to drive the grids of the 833s. Not a lot of trouble considering the HV transistors that we have today. The FETs and bipolar transistors have better characteristics for that sort of thing than the 807s they used back then. I would never go to a class B or AB2 grids with out my transistor drivers. See http://www.qsl.net/wa5bxo/driver1.html I have always wanted to try the inverse feed back circuits that RCA and Gates used on the modulators. But I never have. I once had the schematic diagram of the Gates 1KW but lost it in the flood of 94. I'm sure there are a lot of ways to do it I just have never taken the time to try. BTW I think your right. I have learned a lot more from stuff that didn't work out quite right. I think the most time consuming thing I ever did was to neutralize a single triode using an inductor from plate to grid (in series with a blocking cap of course. The inductor resonates with the G - P capacitance of the tube. Let me say "It Works very well, but it is not my first choice for construction mechanics, plus it has to be tuned every time you change frequency.) 73, John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Sunday, November 30, 2003 9:41 PM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Re: Modulation transformer ID and repair The push pull parallel 100TH deck does take quite a bit of driving power, with the losses, likely close to 20 watts, which is what the UTC LS grid transformer is good for. That may be part of the problem, but class B triodes always seem to sound less clean than a good AB1 amp. Brett N2DTS
RE: [AMRadio] Re: Modulation transformer ID and repair
The push pull parallel 100TH deck does take quite a bit of driving power, with the losses, likely close to 20 watts, which is what the UTC LS grid transformer is good for. That may be part of the problem, but class B triodes always seem to sound less clean than a good AB1 amp. Brett N2DTS > > > I have been on vacation to visit the grandkids in Arkansas. > Sorry about > the late reply. > I agree on the blatant abuse VS occasional over the limit. I > feel that the main thing is to keep the signal as clean as possible on > bandwidth due to distortion and phasing products and just be > a gentleman > about all. Consider the other guys interests etc. These are > interesting thoughts though. > I have been altering the shape of the wave form at a low level > point to more equalize the symmetry. I have found it to be a more > soothing sound as most report when there is no QSB or noise but the > unmodified voice at full negative modulation and positive peaks where > the may be, has the most readability when the going is a > little rougher. > > I can't help but think the difference in the sounds of your > modulation decks must be in the flow of grid current VS AB1, plus just > because a triode has a low Rp doesn't necessarily make it as > linier as a > tetrode in the same application and load. As a matter of fact I think > tetrodes especially beam tetrodes make exception modulators. A > modulator doesn't have to work into a varying load over one > audio cycle > and should see the same load over all the audio frequencies (hence my > concern over having enough cap and choke for the modulation > reactor and > coupling cap). Since the load is near constant and there is > no damping > required then tetrodes should be superior modulators especially if one > could put a little inverse feed back on them. I plan on experimenting > with that in the future as well and with AB1 at the grid it should be > easy to do. > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski > Sent: Wednesday, November 26, 2003 7:14 AM > To: amradio@mailman.qth.net > Subject: RE: [AMRadio] Re: Modulation transformer ID and repair > > Both mod decks are hooked up to the RF deck all the time. > They both get high voltage, but I only turn one on at a time. > Both are driven by the same 120 watt 8 ohm power amp, into LS > output transformers (right and left channels), as is the 811 > mod deck in > the pp 812 rig. > All the transmitters should sound the same, since the same audio feeds > them. > The 4x150 (or 4cx250b) sounds best, in AB1. > Yes, lots of current, 500ma at 1000 or 2000 volts, 250 ma each tube. > > I have tried just two 100TH tubes, different plate voltages (variac in > power > supply), > yet it just never sounds as clean as the 4x150 deck. > > I can also run 100TL tubes, and tried them, same sound. > > People over the air cant hear a difference, they say, but its quite > audible in the mod monitor. > > My voice is also lop sided, but not as much as yours! > I get the best peaks on the 813/4x150 combo, I don't know what > the actual reading is, as the pep wattmeter only goes up to > 2000 watts, > and I have to guestimate by how hard the needle slams into the stop, > but expect its not much over 2500 watts at 600 watts carrier. > > If I was to run the rig at 2000 watts pep, would anyone know or care > that I was exceeding the power limit (by a little bit)??? > > In your case, I would try to limit the positive peaks, say equal > to the negative peaks, and run about 90% modulation. > This will give good audio percentage and a strong carrier. > Positive peaks are good, but I don't think they are effective > on the air, if you have to limit the negative mod and the pep. > better to make sure you go 90% negative at least, and > whatever positive, > lower is better to keep it under 1500 watts, although I doubt the FCC > truck will pull up outside the house if you go over 1500 watts pep. > If you ran 10,000 watts pep, someone might notice eventually, but they > Really should pay more attention to the intentional > interference on the > bands. > > I personally don't think they pay any attention to anything other than > Blatant abuse over a long time, and even then, they seem to > play games, > warnings, going to court, etc. > > > > > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio
RE: [AMRadio] Re: Modulation transformer ID and repair
Thanks Jim I never though I'd be accused of having a perfect voice. HIHI Actually I only add a little RC phase shifting in the lower lows. I can actually reverse the peak:trough symmetry with the EQ circuitry but it is not very good sounding like that. So I just shift it a little and it makes the bass have some resonance at a real low freq which makes the air conditioner cause a ripple in the scope. Here lately I'm more interested in getting the antenna up to the 100 ft level with an apex angle of more that 20 degrees. Now that the green stuff has quit growing I have been chopping the vines to try to make a path between the tower and the tree that will hold up the north leg of the doublet. John WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Candela Sent: Sunday, November 30, 2003 10:45 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Re: Modulation transformer ID and repair John, I like the way you sound without any processing to make the modulation more symmetrical. Some of us go through great length to taylor the audio to get that kind of asymmetry, and with you the audio from your raw voice is "perfect".
RE: [AMRadio] Re: Modulation transformer ID and repair
John, I like the way you sound without any processing to make the modulation more symmetrical. Some of us go through great length to taylor the audio to get that kind of asymmetry, and with you the audio from your raw voice is "perfect". You might add a speech polarity reversing switch, and if the FCC ever challenges you, flick the switch, and back off the audio until the negative modulation is less than 100%, and say there, what are you guys talking about? :) PS: Or maybe run maximum carrier, and run NBFM, or PM. I am currently running PM, and had a two way with a fellow on NBFM last night. He had true FM detection, and said It sounded like 2 meters FM, with almost 100% silencing of background noise... Regards, Jim Candela WD5JKO "John Coleman, ARS WA5BXO" <[EMAIL PROTECTED]> wrote: I have been on vacation to visit the grandkids in Arkansas. Sorry about the late reply. I agree on the blatant abuse VS occasional over the limit. I feel that the main thing is to keep the signal as clean as possible on bandwidth due to distortion and phasing products and just be a gentleman about all. Consider the other guys interests etc. These are interesting thoughts though. I have been altering the shape of the wave form at a low level point to more equalize the symmetry. I have found it to be a more soothing sound as most report when there is no QSB or noise but the unmodified voice at full negative modulation and positive peaks where the may be, has the most readability when the going is a little rougher. I can't help but think the difference in the sounds of your modulation decks must be in the flow of grid current VS AB1, plus just because a triode has a low Rp doesn't necessarily make it as linier as a tetrode in the same application and load. As a matter of fact I think tetrodes especially beam tetrodes make exception modulators. A modulator doesn't have to work into a varying load over one audio cycle and should see the same load over all the audio frequencies (hence my concern over having enough cap and choke for the modulation reactor and coupling cap). Since the load is near constant and there is no damping required then tetrodes should be superior modulators especially if one could put a little inverse feed back on them. I plan on experimenting with that in the future as well and with AB1 at the grid it should be easy to do. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Wednesday, November 26, 2003 7:14 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Re: Modulation transformer ID and repair Both mod decks are hooked up to the RF deck all the time. They both get high voltage, but I only turn one on at a time. Both are driven by the same 120 watt 8 ohm power amp, into LS output transformers (right and left channels), as is the 811 mod deck in the pp 812 rig. All the transmitters should sound the same, since the same audio feeds them. The 4x150 (or 4cx250b) sounds best, in AB1. Yes, lots of current, 500ma at 1000 or 2000 volts, 250 ma each tube. I have tried just two 100TH tubes, different plate voltages (variac in power supply), yet it just never sounds as clean as the 4x150 deck. I can also run 100TL tubes, and tried them, same sound. People over the air cant hear a difference, they say, but its quite audible in the mod monitor. My voice is also lop sided, but not as much as yours! I get the best peaks on the 813/4x150 combo, I don't know what the actual reading is, as the pep wattmeter only goes up to 2000 watts, and I have to guestimate by how hard the needle slams into the stop, but expect its not much over 2500 watts at 600 watts carrier. If I was to run the rig at 2000 watts pep, would anyone know or care that I was exceeding the power limit (by a little bit)??? In your case, I would try to limit the positive peaks, say equal to the negative peaks, and run about 90% modulation. This will give good audio percentage and a strong carrier. Positive peaks are good, but I don't think they are effective on the air, if you have to limit the negative mod and the pep. better to make sure you go 90% negative at least, and whatever positive, lower is better to keep it under 1500 watts, although I doubt the FCC truck will pull up outside the house if you go over 1500 watts pep. If you ran 10,000 watts pep, someone might notice eventually, but they Really should pay more attention to the intentional interference on the bands. I personally don't think they pay any attention to anything other than Blatant abuse over a long time, and even then, they seem to play games, warnings, going to court, etc. ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio --- StripMime Report -- processed MIME parts --- multipart/alternative text/plain (text body -- kept) text/html The
RE: [AMRadio] Re: Modulation transformer ID and repair
I have been on vacation to visit the grandkids in Arkansas. Sorry about the late reply. I agree on the blatant abuse VS occasional over the limit. I feel that the main thing is to keep the signal as clean as possible on bandwidth due to distortion and phasing products and just be a gentleman about all. Consider the other guys interests etc. These are interesting thoughts though. I have been altering the shape of the wave form at a low level point to more equalize the symmetry. I have found it to be a more soothing sound as most report when there is no QSB or noise but the unmodified voice at full negative modulation and positive peaks where the may be, has the most readability when the going is a little rougher. I can't help but think the difference in the sounds of your modulation decks must be in the flow of grid current VS AB1, plus just because a triode has a low Rp doesn't necessarily make it as linier as a tetrode in the same application and load. As a matter of fact I think tetrodes especially beam tetrodes make exception modulators. A modulator doesn't have to work into a varying load over one audio cycle and should see the same load over all the audio frequencies (hence my concern over having enough cap and choke for the modulation reactor and coupling cap). Since the load is near constant and there is no damping required then tetrodes should be superior modulators especially if one could put a little inverse feed back on them. I plan on experimenting with that in the future as well and with AB1 at the grid it should be easy to do. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Wednesday, November 26, 2003 7:14 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Re: Modulation transformer ID and repair Both mod decks are hooked up to the RF deck all the time. They both get high voltage, but I only turn one on at a time. Both are driven by the same 120 watt 8 ohm power amp, into LS output transformers (right and left channels), as is the 811 mod deck in the pp 812 rig. All the transmitters should sound the same, since the same audio feeds them. The 4x150 (or 4cx250b) sounds best, in AB1. Yes, lots of current, 500ma at 1000 or 2000 volts, 250 ma each tube. I have tried just two 100TH tubes, different plate voltages (variac in power supply), yet it just never sounds as clean as the 4x150 deck. I can also run 100TL tubes, and tried them, same sound. People over the air cant hear a difference, they say, but its quite audible in the mod monitor. My voice is also lop sided, but not as much as yours! I get the best peaks on the 813/4x150 combo, I don't know what the actual reading is, as the pep wattmeter only goes up to 2000 watts, and I have to guestimate by how hard the needle slams into the stop, but expect its not much over 2500 watts at 600 watts carrier. If I was to run the rig at 2000 watts pep, would anyone know or care that I was exceeding the power limit (by a little bit)??? In your case, I would try to limit the positive peaks, say equal to the negative peaks, and run about 90% modulation. This will give good audio percentage and a strong carrier. Positive peaks are good, but I don't think they are effective on the air, if you have to limit the negative mod and the pep. better to make sure you go 90% negative at least, and whatever positive, lower is better to keep it under 1500 watts, although I doubt the FCC truck will pull up outside the house if you go over 1500 watts pep. If you ran 10,000 watts pep, someone might notice eventually, but they Really should pay more attention to the intentional interference on the bands. I personally don't think they pay any attention to anything other than Blatant abuse over a long time, and even then, they seem to play games, warnings, going to court, etc.
RE: [AMRadio] Re: Modulation transformer ID and repair
Don, I don't get into the negative cycle loading much, its more of a protection device, to prevent splatter and so on. I think anything that changes the input waveform is distortion. I do run some compression, to compensate for moving around while talking. The mike preamp does limit the peaks (one of those berringer things), but not much. Brett N2DTS > > >I limit my quick peaks in the mike preamp, and include negative > >cycle loading in all RF decks, but don't push things much. > > I don't use negative cycle loading or ultramodulation, but I do take > advantage of the natural asymmetry of the human voice. Mine > tends to run > about 135% positive when I limit the negative to 100%. The > ratio would be > more like 2:1 if I clipped off a few excessive negative > peaks. I usually run > about 640 watts DC input to the final. Considering the > losses in the PA > tank circuit, the matching network at the transmitter output, > the feedline > between the shack and the tower site, and the remote antenna > tuner at the > base of the tower, I'd be surprised if I'm getting as much > as 400 watts > carrier output to the antenna. When I talk, the modulatior > plate meters > just barely wiggle beyond static plate current, unless I > whistle or make a > sustained tone. With a sinewave signal from a generator I > can make each > modulator tube draw up to 400 ma! The only "processing" I use is the > Universal Audio/Urei Model BL-40 Modulimiter (the only > solid-state device in > the station except for the homebrew cw keyer). > > > >There are people on the band who run/can run excessive positive > >modulation, but you need a special detector I guess, because > they sound > >bad in my shack when they do. > > I just make sure there is no flat-topping on positive peaks > or bright spots > on the baseline in the negative direction. I once tried > ultramodulation, > but I think I gained much more distortion than talk power. > Most reports > indicated the audio was no louder, but had a scratchy sound. > The most > effective thing I ever tried for "talk power" was high level > symmetrical > speech clipping back in the 60's, but it added audible > distortion, and I > went through about half a dozen modulation transformers in > about as many > months, ranging in ratings from 500 to 2000 watts. After I > abandoned the > high level clipping, I havn't lost a single modulation > transformer since. > > Don K4KYV >
RE: [AMRadio] Re: Modulation transformer ID and repair
I limit my quick peaks in the mike preamp, and include negative cycle loading in all RF decks, but don't push things much. I don't use negative cycle loading or ultramodulation, but I do take advantage of the natural asymmetry of the human voice. Mine tends to run about 135% positive when I limit the negative to 100%. The ratio would be more like 2:1 if I clipped off a few excessive negative peaks. I usually run about 640 watts DC input to the final. Considering the losses in the PA tank circuit, the matching network at the transmitter output, the feedline between the shack and the tower site, and the remote antenna tuner at the base of the tower, I'd be surprised if I'm getting as much as 400 watts carrier output to the antenna. When I talk, the modulatior plate meters just barely wiggle beyond static plate current, unless I whistle or make a sustained tone. With a sinewave signal from a generator I can make each modulator tube draw up to 400 ma! The only "processing" I use is the Universal Audio/Urei Model BL-40 Modulimiter (the only solid-state device in the station except for the homebrew cw keyer). There are people on the band who run/can run excessive positive modulation, but you need a special detector I guess, because they sound bad in my shack when they do. I just make sure there is no flat-topping on positive peaks or bright spots on the baseline in the negative direction. I once tried ultramodulation, but I think I gained much more distortion than talk power. Most reports indicated the audio was no louder, but had a scratchy sound. The most effective thing I ever tried for "talk power" was high level symmetrical speech clipping back in the 60's, but it added audible distortion, and I went through about half a dozen modulation transformers in about as many months, ranging in ratings from 500 to 2000 watts. After I abandoned the high level clipping, I havn't lost a single modulation transformer since. Don K4KYV _ Share holiday photos without swamping your Inbox. Get MSN Extra Storage now! http://join.msn.com/?PAGE=features/es
RE: [AMRadio] Re: Modulation transformer ID and repair
Don, Well, I don't care about modulator efficiency at all. I like to have at least the input power of the rf deck available as modulator power if possible. On the 813 rig, I run 2000 volts at .4 amps, 800 watts input. I only have 600 watts out of the 4x150a mod deck, but the ppp 100th deck could do more I guess, 900 watts at 3000 volts. On the 812 rig, I have 811a modulators at 1500 volts, supposed to put out over 300 watts, so I am good there. I limit my quick peaks in the mike preamp, and include negative cycle loading in all RF decks, but don't push things much. I should turn the plate voltage on the 813 rig down, run lower output power, and see what the peaks get up to. As it is now, I cant measure them, they are off the 2000 watt scale, but suspect they run 4 to 1- 600 watts out would give 2400 pep. But it all depends on how loud I talk, when the FCC truck pulls up, speak softly and carry a big stick There are people on the band who run/can run excessive positive modulation, but you need a special detector I guess, because they sound bad in my shack when they do. The best sounding signals to me sound quite natural and mellow. WA3VJB and another guy were on 80 a few days ago, good conditions, good subject matter, wonderful to listen to while doing odds and ends in the shack. STRONG carriers and mellow modulation. Brett N2DTS Brett N2DTS > > I agree wholeheartedly. Also, careful examination of the > wording of Part 97 > reveals that the regs define the pep figure as "under normal > conditions". > Most of the time the voice remains at a fairly low value of > voice peaks > (about 30% modulation), with a few reaching 100% while an > occasional peak > attempts to go sky high. These exceptional peaks add next to > nothing to the > total sideband power or the interference potential of the > signal. It's > where the majority of peaks go, along with the modulation > density of the > audio that determines how loud a signal is. That is what could be > interpreted as "under normal conditions". > > One advantage of modulating down to just below 100% negative > and letting the > positive peaks go where they may is a cleaner signal. With > limited positive > peaks (most transmitters are not capable of modulating much > more than 100% > if even that much), the temptation is to modulate to 100% in > the negative > direction, and let the occasional high positive peaks clip off at the > maximum positive modulation capability of the transmitter. > It is very > difficult to even see the positive peak clipping on the > envelope pattern of > a scope unless you drive the audio so high that a large > percentage of the > dominant peaks are flat-topped. If a transmitter is capable > of 150 or 200% > positive peaks to accomodate the occasional wayward peak > (comprising less > that 1% of the total number of positive peaks), there will be > no splatter > resulting from the hard clipping of these miniscule peaks. > When these peaks > are clipped, as in the case of 99% of the AM transmitters on > the air, both > amateur and broadcast, they add to the spurious sideband > components of the > signal, even though the clipping effect may otherwise be > inaudible and > invisible on the envelope pattern. > > A disadvantage of high positive peak capability is low > modulator efficiency. > A class-B amplifier's efficiency is directly proportional to signal > amplitude, reaching a maximum at peak output capability. If > the modulator > is capable of delivering peaks at 200% modulation, but you > run it at about > 100% most of the time, the average efficiency will be much > less than that of > an amplifier capable of delivering only 100% at its peak > output. However, > the duty cycle of human speech is so low that this will make > very little > difference in the ratio of overall 60~ a.c. power input to > r.f. output > delivered to the antenna. > > One of the early double-sideband schemes just after WWII > described in QST by > Villard employed the "upside-down tube" circuit. Although this was > exploited later to make the signal louder by transmitting DSB reduced > carrier, keeping the DC input within the 1 kw limit while > generating several > kilowatts of sideband power, the original intent of the > scheme was to take > care of occasional negative overmodulation peaks without > generating suprious > sideband products. The article was entitiled "overmodulation without > splatter". The sole purpose of the original proposal was to > clean up the > signal back in the days when few hams had monitor scopes or > fully understood > the principles of modulation, and the phone bands were full > of trash from > overmodulated signals. > > I think some AM'ers are overly paranoid about p.e.p. I > wonder if these same > folks are as cautious about going even 1 mph over the posted > speed limit > while driving their automobiles; certainly driving a 4000-lb. > machine beyond > the legal speed limit on a public highway causes gr
RE: [AMRadio] Re: Modulation transformer ID and repair
Brett Gazdzinski <[EMAIL PROTECTED]> said: If I was to run the rig at 2000 watts pep, would anyone know or care that I was exceeding the power limit (by a little bit)??? Positive peaks are good, but I don't think they are effective on the air, if you have to limit the negative mod and the pep. better to make sure you go 90% negative at least, and whatever positive, ... although I doubt the FCC truck will pull up outside the house if you go over 1500 watts pep. If you ran 10,000 watts pep, someone might notice eventually, but they really should pay more attention to the intentional interference on the bands. I personally don't think they pay any attention to anything other than blatant abuse over a long time, and even then, they seem to play games, warnings, going to court, etc. I did track down Ron boot (anyone remember him?), go over his house, and confront him face to face. he turned REAL nice and gave me a tour of his shack (junk). I told him, I know where you live, and can come back anytime day or night, and although I am mellow and tolerant, I can pound your face if I get pissed enough. The FCC had gone after him somewhat, with zero results ((Kinda like the current farce on 3890 kc/s? - Don)), so I personally don't worry about going slightly over 1500 watts pep. >My voice is so lopsided; it has peaks 2 squares pos on the scope > for one square down. I've tried it on many scopes direct > from many good > microphones. When connecting the same mic to the rig, a 600 watt > carrier output yields 5400 watts PEP output just as the carrier is > pinched on the 100% negative cylce. I agree wholeheartedly. Also, careful examination of the wording of Part 97 reveals that the regs define the pep figure as "under normal conditions". Most of the time the voice remains at a fairly low value of voice peaks (about 30% modulation), with a few reaching 100% while an occasional peak attempts to go sky high. These exceptional peaks add next to nothing to the total sideband power or the interference potential of the signal. It's where the majority of peaks go, along with the modulation density of the audio that determines how loud a signal is. That is what could be interpreted as "under normal conditions". One advantage of modulating down to just below 100% negative and letting the positive peaks go where they may is a cleaner signal. With limited positive peaks (most transmitters are not capable of modulating much more than 100% if even that much), the temptation is to modulate to 100% in the negative direction, and let the occasional high positive peaks clip off at the maximum positive modulation capability of the transmitter. It is very difficult to even see the positive peak clipping on the envelope pattern of a scope unless you drive the audio so high that a large percentage of the dominant peaks are flat-topped. If a transmitter is capable of 150 or 200% positive peaks to accomodate the occasional wayward peak (comprising less that 1% of the total number of positive peaks), there will be no splatter resulting from the hard clipping of these miniscule peaks. When these peaks are clipped, as in the case of 99% of the AM transmitters on the air, both amateur and broadcast, they add to the spurious sideband components of the signal, even though the clipping effect may otherwise be inaudible and invisible on the envelope pattern. A disadvantage of high positive peak capability is low modulator efficiency. A class-B amplifier's efficiency is directly proportional to signal amplitude, reaching a maximum at peak output capability. If the modulator is capable of delivering peaks at 200% modulation, but you run it at about 100% most of the time, the average efficiency will be much less than that of an amplifier capable of delivering only 100% at its peak output. However, the duty cycle of human speech is so low that this will make very little difference in the ratio of overall 60~ a.c. power input to r.f. output delivered to the antenna. One of the early double-sideband schemes just after WWII described in QST by Villard employed the "upside-down tube" circuit. Although this was exploited later to make the signal louder by transmitting DSB reduced carrier, keeping the DC input within the 1 kw limit while generating several kilowatts of sideband power, the original intent of the scheme was to take care of occasional negative overmodulation peaks without generating suprious sideband products. The article was entitiled "overmodulation without splatter". The sole purpose of the original proposal was to clean up the signal back in the days when few hams had monitor scopes or fully understood the principles of modulation, and the phone bands were full of trash from overmodulated signals. I think some AM'ers are overly paranoid about p.e.p. I wonder if these same folks are as cautious about going even 1 mph over the posted speed limit whi
RE: [AMRadio] Re: Modulation transformer ID and repair
never draw and grid current at > the low level we run them these days. I run about 2500 volts on the > plates and 800 on the screens setting the bias to idle total cathode > current of about 100 ma. They show just a tiny little color on the > plates. > > John, > WA5BXO > > > > -Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski > Sent: Tuesday, November 25, 2003 2:33 PM > To: amradio@mailman.qth.net > Subject: RE: [AMRadio] Re: Modulation transformer ID and repair > > Well, the 813 rig seems to be clean in the audio > department, and gets nice positive peaks, over 130% positive, > and I can get 2500 watts pep out of a 600 watt carrier, but > will try a bigger audio cap and see if it sounds better... > > When I run the push pull parallel 100TH deck, the audio does > NOT sound as clean, its not bad, its just not as clean as the 4x150a > mod deck. > Resting current and plate voltage does not seem to change the sound, > I tried various settings and so on. > > Brett > N2DTS > > > > > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio
RE: [AMRadio] Re: Modulation transformer ID and repair
My voice is so lopsided; it has peaks 2 squares pos on the scope for one square down. I've tried it on many scopes direct from many good microphones. When connecting the same mic to the rig, a 600 watt carrier output yields 5400 watts PEP output just as the carrier is pinched on the 100% negative cylce. If I switch the polarity of the microphone it all goes downward and pinches the carrier with only a PEP of about 700-600 watts. I was very careful to maintain the linearity and phase of the audio all the way through to the output of the modulator so that in the old days when we ran 1KW input and got 800 or more out of the high efficiency finals the PEP was 3 squared for me not 2. I am now toying with the idea of reversing the phase of the mic and increasing the carrier to about 1200 watts to yield 1500 PEP, just to see how it works that way. Same amount of sideband power just more carrier. It probably won't sound as heavily modulated nut I wonder if it will take out more noise and make diode detection cleaner. About your modulator decks, do they each have there on modulation XFMR or is the modulation XFMR common to both. As for the different sounds for each one, there may be many variables I am not aware of. I assume the quad 100th modulator is AB2 of B and requires some driving power where as the 4X150 are probably AB1. so there may be different driving techniques. I don't know what the peak current capability for either of those tubes is for a given drive voltage. I used quad 4CX300s once for modulators and boy did that thing have the current swing capability, and in AB1 even. The sockets were a bear though. I had to make adapters with octal plugs on them. I was given the tubes and have no idea what the real socket even looks like. I now use quad 813s in AB1 although they will do AB2 just fine. They just never draw and grid current at the low level we run them these days. I run about 2500 volts on the plates and 800 on the screens setting the bias to idle total cathode current of about 100 ma. They show just a tiny little color on the plates. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Tuesday, November 25, 2003 2:33 PM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Re: Modulation transformer ID and repair Well, the 813 rig seems to be clean in the audio department, and gets nice positive peaks, over 130% positive, and I can get 2500 watts pep out of a 600 watt carrier, but will try a bigger audio cap and see if it sounds better... When I run the push pull parallel 100TH deck, the audio does NOT sound as clean, its not bad, its just not as clean as the 4x150a mod deck. Resting current and plate voltage does not seem to change the sound, I tried various settings and so on. Brett N2DTS
RE: [AMRadio] Re: Modulation transformer ID and repair
WA3JVJ bought 3 or 4 cvm5 mod transformers, and gave me one. Out of the 4, he happened to give me one that is totally quiet all the time, dc through it or not... Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Donald Chester > Sent: Tuesday, November 25, 2003 6:49 PM > To: amradio@mailman.qth.net > Subject: RE: [AMRadio] Re: Modulation transformer ID and repair > > > > > >I cant say removing the current from the cvm5 seemed to help > the sound > >of the rig much. > > > > I tried it with an older version, the VM-5. It didn't > radically affect the > sound of the rig over the air, but with the DC thru the > winding, it talked > back like a speaker in the transmitter cabinet. I couldn't > crack up the > audio without accoustical feedback. With the reactor, the > VM-5 was quiet > as a mouse, and the waveform at low audio frequencies (< > 100~) looked more > symmetrical on the scope. I haven't run DC through a > modulation transformer > secondary since about 1963. > > _ > Need a shot of Hank Williams or Patsy Cline? The classic > country stars are > always singing on MSN Radio Plus. Try one month free! > http://join.msn.com/?page=offers/premiumradio > > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] Re: Modulation transformer ID and repair
> > > 3000VDC @ 300mA = 10,000 ohms. (This is where the transmitter lives > > > according to the notes I have on it) > > > > > >perhaps thats what it's capable of, but you're not going to run it there > >are ya? > > That's what the first high power homebrew rig I remember ever actually > seeing ran - an old fellow in Kentucky. He used a pair of 100TH's in the > final, modulated with a pair of triode connected 813's and a homebrew > modulation transformer. His audio sounded like a tin can, but did he strap! > > His rig inspired me to build a single 304TL final moulated first by a pair > of 211's (@ 600w input) then later with triode/813's then 810's and later, > 833-A's. My 866A's kept flashing over @ 3000 volts, using a pole pig, so I > settled for 2500v @ 400 ma. Besides that gave a better match to the > modulation transformer. I remember the days as well as some others here when we all said "When AM Kilowatts are outlawed, then only Outlaws will have AM Kilowatts." The point being, Don, the power limit now is 1500w PEP output. Like it or not, that's the "Law". So, when I said "you're not going to run it at that level", I meant by keeping the output level down to 1500w PEP output. Even with the Asymetrical audio study and research that has been done, I'm not above running 500w DC input, with an SR of 3. However, runing a full kW, with an SR of 3 is ASKING for trouble, unless that particular transmitter has the phase reversed. The result is more carrier (which makes it sound better, for "eliminating the static") with just as much audio. Mathematically speaking, lower current in the final will result in lower current on the secondary of the modulation transformer, which results in more audio energy in the sidebands. 73 = Best Regards, -Geoff/W5OMR
RE: [AMRadio] Re: Modulation transformer ID and repair
I cant say removing the current from the cvm5 seemed to help the sound of the rig much. I tried it with an older version, the VM-5. It didn't radically affect the sound of the rig over the air, but with the DC thru the winding, it talked back like a speaker in the transmitter cabinet. I couldn't crack up the audio without accoustical feedback. With the reactor, the VM-5 was quiet as a mouse, and the waveform at low audio frequencies (< 100~) looked more symmetrical on the scope. I haven't run DC through a modulation transformer secondary since about 1963. _ Need a shot of Hank Williams or Patsy Cline? The classic country stars are always singing on MSN Radio Plus. Try one month free! http://join.msn.com/?page=offers/premiumradio
Re: [AMRadio] Re: Modulation transformer ID and repair
From: "Geoff/W5OMR" <[EMAIL PROTECTED]> > 3000VDC @ 300mA = 10,000 ohms. (This is where the transmitter lives > according to the notes I have on it) perhaps thats what it's capable of, but you're not going to run it there are ya? That's what the first high power homebrew rig I remember ever actually seeing ran - an old fellow in Kentucky. He used a pair of 100TH's in the final, modulated with a pair of triode connected 813's and a homebrew modulation transformer. His audio sounded like a tin can, but did he strap! His rig inspired me to build a single 304TL final moulated first by a pair of 211's (@ 600w input) then later with triode/813's then 810's and later, 833-A's. My 866A's kept flashing over @ 3000 volts, using a pole pig, so I settled for 2500v @ 400 ma. Besides that gave a better match to the modulation transformer. Don K4KYV _ Say goodbye to busy signals and slow downloads with a high-speed Internet connection! Prices start at less than $1 a day average. https://broadband.msn.com (Prices may vary by service area.)
RE: [AMRadio] Re: Modulation transformer ID and repair
Well, the 813 rig seems to be clean in the audio department, and gets nice positive peaks, over 130% positive, and I can get 2500 watts pep out of a 600 watt carrier, but will try a bigger audio cap and see if it sounds better... When I run the push pull parallel 100TH deck, the audio does NOT sound as clean, its not bad, its just not as clean as the 4x150a mod deck. Resting current and plate voltage does not seem to change the sound, I tried various settings and so on. Brett N2DTS > > > I agree on the explosion Brett! > > If the choke and coupling cap are both large enough > there should be > no change in the output waveform than if it were connected to > a resistive > load. Perhaps it is the capacitance of the choke windings > that is throwing > it off. It would be interesting to know what the free > resonance of the > choke is. Or perhaps too much RF bypass capacitance in the > RF deck. At any > rate I can't help but think that a smaller coupling cap would create > resonance which would put a reactive load on the modulator as > would too > little reactor. This would make the modulator to see a > different load Z > depending on modulating frequencies. In turn there would be > intermodulation > distortion. And a shift in phase relationships of frequencies > that make a > certain wave shape. > > Interesting subject! > > John, WA5BXO > > > > > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Tuesday, November 25, 2003 11:03 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Re: Modulation transformer ID and repair I was talking about the pass capacitor, using a big one seemed to interact with the choke and mod iron, a big cap had the sound muffled, or something, I was disappointed with the results. I tried changing the size of the cap, and found 4 uf I think sounded natural. I had tried all the way up to 40 UF. The power supply has 70 uf or more in it... Now that I actually have a good mike and preamp, maybe I should try other values again. More farads in the power supply is always better, but you need step start or some way to bring it up gently. Some run the voltage on all the time and switch the cathode, I never tried that, easy with triodes likely, not sure about tetrodes WA3JVJ has a push pull parallel 805 mod deck with a huge string of computer type caps, gives a full farad or more, and he runs the voltage on all the time. I think its quite crazy, about 60 computer grade caps in series parallel, at 2000 volts or whatever, if one cap fails, the explosion and mess will likely be very nasty! Brett N2DTS t/mailman/listinfo/amradio ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
RE: [AMRadio] Re: Modulation transformer ID and repair
I agree on the explosion Brett! If the choke and coupling cap are both large enough there should be no change in the output waveform than if it were connected to a resistive load. Perhaps it is the capacitance of the choke windings that is throwing it off. It would be interesting to know what the free resonance of the choke is. Or perhaps too much RF bypass capacitance in the RF deck. At any rate I can't help but think that a smaller coupling cap would create resonance which would put a reactive load on the modulator as would too little reactor. This would make the modulator to see a different load Z depending on modulating frequencies. In turn there would be intermodulation distortion. And a shift in phase relationships of frequencies that make a certain wave shape. Interesting subject! John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Tuesday, November 25, 2003 11:03 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Re: Modulation transformer ID and repair I was talking about the pass capacitor, using a big one seemed to interact with the choke and mod iron, a big cap had the sound muffled, or something, I was disappointed with the results. I tried changing the size of the cap, and found 4 uf I think sounded natural. I had tried all the way up to 40 UF. The power supply has 70 uf or more in it... Now that I actually have a good mike and preamp, maybe I should try other values again. More farads in the power supply is always better, but you need step start or some way to bring it up gently. Some run the voltage on all the time and switch the cathode, I never tried that, easy with triodes likely, not sure about tetrodes WA3JVJ has a push pull parallel 805 mod deck with a huge string of computer type caps, gives a full farad or more, and he runs the voltage on all the time. I think its quite crazy, about 60 computer grade caps in series parallel, at 2000 volts or whatever, if one cap fails, the explosion and mess will likely be very nasty! Brett N2DTS t/mailman/listinfo/amradio
RE: [AMRadio] Re: Modulation transformer ID and repair
I was talking about the pass capacitor, using a big one seemed to interact with the choke and mod iron, a big cap had the sound muffled, or something, I was disappointed with the results. I tried changing the size of the cap, and found 4 uf I think sounded natural. I had tried all the way up to 40 UF. The power supply has 70 uf or more in it... Now that I actually have a good mike and preamp, maybe I should try other values again. More farads in the power supply is always better, but you need step start or some way to bring it up gently. Some run the voltage on all the time and switch the cathode, I never tried that, easy with triodes likely, not sure about tetrodes WA3JVJ has a push pull parallel 805 mod deck with a huge string of computer type caps, gives a full farad or more, and he runs the voltage on all the time. I think its quite crazy, about 60 computer grade caps in series parallel, at 2000 volts or whatever, if one cap fails, the explosion and mess will likely be very nasty! Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of John Coleman, ARS > WA5BXO > Sent: Tuesday, November 25, 2003 9:25 AM > To: amradio@mailman.qth.net > Subject: RE: [AMRadio] Re: Modulation transformer ID and repair > > > I guess the "more is better statement" is strictly a personal > preference. What I should have said is "If you want the > audio waveform > to not be modified by the output circuitry then more is > better". Having > to little capacitance will modify the audio wave form and can > shift the > phase of lower frequencies for instance if a 200 cps note and > a 400 cps > mote or together and appear as natural harmonic causing > certain peaks of > a non sinusoidal wave to go positive then the shifting of the phase > relationship between these two frequencies may cause a > repositioning of > the peaks and there by cause the loss of the peaks. This can sound > better. I guess for some, better sound is not always the > natural sound. > It can even shift it so that the peaks go negative. This is also done > with certain settings of tonal control circuitry. > > > 73,John, > WA5BXO
RE: [AMRadio] Re: Modulation transformer ID and repair
I guess the "more is better statement" is strictly a personal preference. What I should have said is "If you want the audio waveform to not be modified by the output circuitry then more is better". Having to little capacitance will modify the audio wave form and can shift the phase of lower frequencies for instance if a 200 cps note and a 400 cps mote or together and appear as natural harmonic causing certain peaks of a non sinusoidal wave to go positive then the shifting of the phase relationship between these two frequencies may cause a repositioning of the peaks and there by cause the loss of the peaks. This can sound better. I guess for some, better sound is not always the natural sound. It can even shift it so that the peaks go negative. This is also done with certain settings of tonal control circuitry. 73,John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Tuesday, November 25, 2003 6:57 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Re: Modulation transformer ID and repair I went out an bought a 50 henery choke from Peter Dahl. It cost $200.00 I think, but is very nice. It works fine at 2000 volts and 400 ma on the 813 rig. I noticed that playing with the cap value changed the sound of the transmitter quite a bit, more is not always better. I cant say removing the current from the cvm5 seemed to help the sound of the rig much. Maybe the cvm5 is not so bad to start with... Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Geoff/W5OMR > Sent: Tuesday, November 25, 2003 7:38 AM > To: amradio@mailman.qth.net > Subject: Re: [AMRadio] Re: Modulation transformer ID and repair > > > > > > > Yow! > > > > 3000VDC @ 300mA = 10,000 ohms. (This is where the transmitter lives > > according to the notes I have on it) > > > perhaps thats what it's capable of, but you're not going to > run it there are ya? > > Come up with a more realistic power level, and go from there. > For that > matter, 60 Hy will probably do you nicely, as long as the > iron can handle > series current through them. > > > 10,000 ohms = 80H @ 200 Hz > > I ran 2000V at 250mA for the longest time, with only 40Hy of > choke, and > never had a problem. the highest rating of current thrugh > one of the chokes > was 275mA (whiich is why I stayed down around 250mA - besides, 500w > DC input is ~around~ 350~375w of carrier out... but, man the > positive peaks > I had then... (http://www.qsl.net/wa5bxo/asyam/aam3.html) > > > And I suppose I had better avoid swinging chokes here too. > > > > Anyone have a suitable reactor for sale? I have a couple of > 10's, but > > obviously this would not be near enough. > > > > I guess the main point in putting reactors in series would > be to place > > the highest voltage-rated one at the modulated voltage point. > > Voltage? No... Current? THAT's what carries the mail! > > 73 = Best Regards, > -Geoff/W5OMR > > > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio ___ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
RE: [AMRadio] Re: Modulation transformer ID and repair
I went out an bought a 50 henery choke from Peter Dahl. It cost $200.00 I think, but is very nice. It works fine at 2000 volts and 400 ma on the 813 rig. I noticed that playing with the cap value changed the sound of the transmitter quite a bit, more is not always better. I cant say removing the current from the cvm5 seemed to help the sound of the rig much. Maybe the cvm5 is not so bad to start with... Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Geoff/W5OMR > Sent: Tuesday, November 25, 2003 7:38 AM > To: amradio@mailman.qth.net > Subject: Re: [AMRadio] Re: Modulation transformer ID and repair > > > > > > > Yow! > > > > 3000VDC @ 300mA = 10,000 ohms. (This is where the transmitter lives > > according to the notes I have on it) > > > perhaps thats what it's capable of, but you're not going to > run it there are ya? > > Come up with a more realistic power level, and go from there. > For that > matter, 60 Hy will probably do you nicely, as long as the > iron can handle > series current through them. > > > 10,000 ohms = 80H @ 200 Hz > > I ran 2000V at 250mA for the longest time, with only 40Hy of > choke, and > never had a problem. the highest rating of current thrugh > one of the chokes > was 275mA (whiich is why I stayed down around 250mA - besides, 500w > DC input is ~around~ 350~375w of carrier out... but, man the > positive peaks > I had then... (http://www.qsl.net/wa5bxo/asyam/aam3.html) > > > And I suppose I had better avoid swinging chokes here too. > > > > Anyone have a suitable reactor for sale? I have a couple of > 10's, but > > obviously this would not be near enough. > > > > I guess the main point in putting reactors in series would > be to place > > the highest voltage-rated one at the modulated voltage point. > > Voltage? No... Current? THAT's what carries the mail! > > 73 = Best Regards, > -Geoff/W5OMR > > > ___ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio
Re: [AMRadio] Re: Modulation transformer ID and repair
> Yow! > > 3000VDC @ 300mA = 10,000 ohms. (This is where the transmitter lives > according to the notes I have on it) perhaps thats what it's capable of, but you're not going to run it there are ya? Come up with a more realistic power level, and go from there. For that matter, 60 Hy will probably do you nicely, as long as the iron can handle series current through them. > 10,000 ohms = 80H @ 200 Hz I ran 2000V at 250mA for the longest time, with only 40Hy of choke, and never had a problem. the highest rating of current thrugh one of the chokes was 275mA (whiich is why I stayed down around 250mA - besides, 500w DC input is ~around~ 350~375w of carrier out... but, man the positive peaks I had then... (http://www.qsl.net/wa5bxo/asyam/aam3.html) > And I suppose I had better avoid swinging chokes here too. > > Anyone have a suitable reactor for sale? I have a couple of 10's, but > obviously this would not be near enough. > > I guess the main point in putting reactors in series would be to place > the highest voltage-rated one at the modulated voltage point. Voltage? No... Current? THAT's what carries the mail! 73 = Best Regards, -Geoff/W5OMR
