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Suppressor-grid modulation
I am planning to build a suppressor-grid modulated AM transmitter.
In all the diagrams I have seen they use proper pentodes, i.e. tubes that have a real suppressor grid (e.g. 803). I have seen no diagram using beam power tubes (e.g. 813 or 814) which have beam forming plates instead of the suppressor grid . Before purchasing 803 tubes, I would like to be sure that 813s or 814s are really unsuitable for suppressor-grid modulation. My question is whether, with 813s or 814s, the plate current can be actually controlled by varying the beam forming plates voltage. Does anyone have experience on that issue? 73 Tony I0JX Rome, Italy |
Suppressor-grid modulation
Il 16/01/2011 19.19, Antonio Vernucci ha scritto:
I am planning to build a suppressor-grid modulated AM transmitter. In all the diagrams I have seen they use proper pentodes, i.e. tubes that have a real suppressor grid (e.g. 803). I have seen no diagram using beam power tubes (e.g. 813 or 814) which have beam forming plates instead of the suppressor grid . Before purchasing 803 tubes, I would like to be sure that 813s or 814s are really unsuitable for suppressor-grid modulation. My question is whether, with 813s or 814s, the plate current can be actually controlled by varying the beam forming plates voltage. Does anyone have experience on that issue? 73 Tony I0JX Rome, Italy Hello Tony, de Piero I5SPO. Quite a ( very ) long time ago, i've done an A.M. TX with a Geloso VFO and a class C RL12P35 Wehrmacht pentode, whose characteristics are similar to 1625 ( a.k.a. 807 with 12.6 v filament ), using a carbon mike and a step-up audio transformer. I believe that, using beam tetrodes, there's no way... :-( I know also 813 and 814 ( have 2 pcs ) and these, like 807, are useful for controlled carrier A.M. by modulating screen grid. Do not know 803, but if i remember well, are low power tubes. Used with suppressor modulation, their output will be one fourth of CW rated output, and efficiency is consequently low... :-( HTH, 73, Piero. |
Suppressor-grid modulation
Hello Tony, de Piero I5SPO.
Quite a ( very ) long time ago, i've done an A.M. TX with a Geloso VFO and a class C RL12P35 Wehrmacht pentode, whose characteristics are similar to 1625 ( a.k.a. 807 with 12.6 v filament ), using a carbon mike and a step-up audio transformer. I believe that, using beam tetrodes, there's no way... :-( I know also 813 and 814 ( have 2 pcs ) and these, like 807, are useful for controlled carrier A.M. by modulating screen grid. Do not know 803, but if i remember well, are low power tubes. Used with suppressor modulation, their output will be one fourth of CW rated output, and efficiency is consequently low... :-( HTH, 73, Piero. Hi Piero, the 803 is about the same as the 813, though it has a proper suppressor screen. Other differences are socket (5 pin vs. 7 pin) and maximum frequency (20 MHz against 30 MHz). What I need to know is if any one has ever tried to vary the 813 beam forming plate voltage, so as to verify whether the plate current can so be controlled. If so, I could avoid to purchase the 803s and use the 813s I already have. I know that with suppressor screen modulation output power is about one fourth, but efficiency will not be so low because, in absence of modulation, also the input power decreases (by somewhat less than one fourth). With a pair of 803s (or 813s I hope!) I should obtain about 200W of unmodulated carrier power, peaking at 800W under 100% modulation. I used to have a few RL12P35s, though I never actually used them. A Radio Rivista article by Dante I1DC describes a transmitter using the RL12P50 (a bigger brother of the RL12P35). But all those tubes are too small for well exploiting the potential advantages of suppressor screen modulation. As a matter of fact the advantage of not having to build a powerful modulator becomes more evident when the needed modulator would be real big! 73 Tony I0JX |
Suppressor-grid modulation
"Antonio Vernucci" wrote in message
... Hello Tony, de Piero I5SPO. Quite a ( very ) long time ago, i've done an A.M. TX with a Geloso VFO and a class C RL12P35 Wehrmacht pentode, whose characteristics are similar to 1625 ( a.k.a. 807 with 12.6 v filament ), using a carbon mike and a step-up audio transformer. I believe that, using beam tetrodes, there's no way... :-( I know also 813 and 814 ( have 2 pcs ) and these, like 807, are useful for controlled carrier A.M. by modulating screen grid. Do not know 803, but if i remember well, are low power tubes. Used with suppressor modulation, their output will be one fourth of CW rated output, and efficiency is consequently low... :-( HTH, 73, Piero. Hi Piero, the 803 is about the same as the 813, though it has a proper suppressor screen. Other differences are socket (5 pin vs. 7 pin) and maximum frequency (20 MHz against 30 MHz). What I need to know is if any one has ever tried to vary the 813 beam forming plate voltage, so as to verify whether the plate current can so be controlled. If so, I could avoid to purchase the 803s and use the 813s I already have. I know that with suppressor screen modulation output power is about one fourth, but efficiency will not be so low because, in absence of modulation, also the input power decreases (by somewhat less than one fourth). With a pair of 803s (or 813s I hope!) I should obtain about 200W of unmodulated carrier power, peaking at 800W under 100% modulation. I used to have a few RL12P35s, though I never actually used them. A Radio Rivista article by Dante I1DC describes a transmitter using the RL12P50 (a bigger brother of the RL12P35). But all those tubes are too small for well exploiting the potential advantages of suppressor screen modulation. As a matter of fact the advantage of not having to build a powerful modulator becomes more evident when the needed modulator would be real big! 73 Tony I0JX True pentodes are needed for suppressor grid modulation. The beam forming plates have much less of an effect on plate current and trying to use them for modulation will result in a highly nonlinear modulation waveform. Remember that emission current not going to the plate will instead go to the screen grid. The power dissipation of the screen grid is what seriously limits the use of suppressor modulation. If you already have the sockets for the 813, I would suggest the use of 4E27A/5-125B tubes. The 4E27/Heintz & Kaufman 257B has less plate dissipation, but it too might be suitable. Please let me know if you need datasheets for either of these tubes and for the 803. 73, Barry WA4VZQ wa4vzq(-at-)live(-dot-)com |
Suppressor-grid modulation
True pentodes are needed for suppressor grid modulation. The beam forming
plates have much less of an effect on plate current and trying to use them for modulation will result in a highly nonlinear modulation waveform. Remember that emission current not going to the plate will instead go to the screen grid. The power dissipation of the screen grid is what seriously limits the use of suppressor modulation. If you already have the sockets for the 813, I would suggest the use of 4E27A/5-125B tubes. The 4E27/Heintz & Kaufman 257B has less plate dissipation, but it too might be suitable. Please let me know if you need datasheets for either of these tubes and for the 803. 73, Barry WA4VZQ wa4vzq(-at-)live(-dot-)com Hi Barry, thanks for the tips. However, looking at the tubes characteristics, the main advantage of the 4E27 w.r.t. the 803 is the possibility to work at much higher frequencies (apart form the socket, which can however be simply changed with no need to make extra holes on the chassis). For the rest, it has a lower plate dissipation (65W against 125W), different filament voltage and it costs more (38$ against 25$). I appreciate the screen grid dissipation problem but it is not clear to me why your statement "that emission current not going to the plate will instead go to the screen grid" would not equally apply if the tube has a proper suppressor grid instead of bram forming plates. Could you please clarify? 73 Tony I0JX |
Suppressor-grid modulation
"Antonio Vernucci" wrote in message ... I am planning to build a suppressor-grid modulated AM transmitter. In all the diagrams I have seen they use proper pentodes, i.e. tubes that have a real suppressor grid (e.g. 803). I have seen no diagram using beam power tubes (e.g. 813 or 814) which have beam forming plates instead of the suppressor grid . Before purchasing 803 tubes, I would like to be sure that 813s or 814s are really unsuitable for suppressor-grid modulation. My question is whether, with 813s or 814s, the plate current can be actually controlled by varying the beam forming plates voltage. Does anyone have experience on that issue? This does not answer the question, but is offered as a bit of homebrew lore. After WWII, the 1625's were plentiful and cheap. Some Ham found that with certain brands of 1625's, the suppressor grid was not tied to the cathode inside the glass envelope. The two were tied together inside the tube base. So, after removing the base, the two elements could be separated from each other. The aim was, guess what? Suppressor-grid modulation! I can remember hearing some of these rigs on the air. I don't know just what percentage of modulation was possible, but I remember it being pretty weak. Good strong signal with very low modulation level. The aim had been to use what parts one had, and it surely was an inexpensive way to join the AM crowd! Old Chief Lynn, W7LTQ |
Suppressor-grid modulation
"Antonio Vernucci" wrote in message
. .. True pentodes are needed for suppressor grid modulation. The beam forming plates have much less of an effect on plate current and trying to use them for modulation will result in a highly nonlinear modulation waveform. Remember that emission current not going to the plate will instead go to the screen grid. The power dissipation of the screen grid is what seriously limits the use of suppressor modulation. If you already have the sockets for the 813, I would suggest the use of 4E27A/5-125B tubes. The 4E27/Heintz & Kaufman 257B has less plate dissipation, but it too might be suitable. Please let me know if you need datasheets for either of these tubes and for the 803. 73, Barry WA4VZQ wa4vzq(-at-)live(-dot-)com Hi Barry, thanks for the tips. However, looking at the tubes characteristics, the main advantage of the 4E27 w.r.t. the 803 is the possibility to work at much higher frequencies (apart form the socket, which can however be simply changed with no need to make extra holes on the chassis). For the rest, it has a lower plate dissipation (65W against 125W), different filament voltage and it costs more (38$ against 25$). I appreciate the screen grid dissipation problem but it is not clear to me why your statement "that emission current not going to the plate will instead go to the screen grid" would not equally apply if the tube has a proper suppressor grid instead of bram forming plates. Could you please clarify? 73 Tony I0JX Actually I did _not_ do a good job of explaining this. In a pentode, the suppressor grid controls the ratio of the emission current going to the screen to that going to the plate. It also eliminates the problem of secondary emission. Beam forming plates are specifically designed to control secondary emission, but they have much less of an effect of controlling plate current. Rather than going into detail here, allow me to refer you to Karl Spangenberg's book, "Vacuum Tubes." This book is now available on several websites. Chapter 11 goes into great detail on how both pentodes and beam power tubes work and how they differ. I would also refer you to O. H Schade's classic paper, "Beam Power Tubes," which is also available on many of the same websites. Pete Millet's site is my favorite with many excellent technical books. http://www.pmillett.com One trick to reduce screen grid dissipation in suppressor modulated pentodes is to power the screen grid with a voltage dropping resistor from the plate supply rather than use an independent supply. While not available in power tubes, many receiving pentodes are designed such that the suppressor grid acts much like the grid in terms of its transconductance. The 6AS6 is probably the earliest example of such tubes. They make good mixers. 73, Barry WA4VZQ |
Suppressor-grid modulation
"coffelt2" wrote in message
... This does not answer the question, but is offered as a bit of homebrew lore. After WWII, the 1625's were plentiful and cheap. Some Ham found that with certain brands of 1625's, the suppressor grid was not tied to the cathode inside the glass envelope. The two were tied together inside the tube base. So, after removing the base, the two elements could be separated from each other. The aim was, guess what? Suppressor-grid modulation! I can remember hearing some of these rigs on the air. I don't know just what percentage of modulation was possible, but I remember it being pretty weak. Good strong signal with very low modulation level. The aim had been to use what parts one had, and it surely was an inexpensive way to join the AM crowd! Old Chief Lynn, W7LTQ In the 1957 ARRL Handbook, these particular tubes were also used in a cathode driven (grounded grid) amplifier. 73, Barry WA4VZQ |
Suppressor-grid modulation
Actually I did _not_ do a good job of explaining this. In a pentode, the
suppressor grid controls the ratio of the emission current going to the screen to that going to the plate. It also eliminates the problem of secondary emission. Beam forming plates are specifically designed to control secondary emission, but they have much less of an effect of controlling plate current. Rather than going into detail here, allow me to refer you to Karl Spangenberg's book, "Vacuum Tubes." This book is now available on several websites. Chapter 11 goes into great detail on how both pentodes and beam power tubes work and how they differ. I would also refer you to O. H Schade's classic paper, "Beam Power Tubes," which is also available on many of the same websites. Pete Millet's site is my favorite with many excellent technical books. http://www.pmillett.com One trick to reduce screen grid dissipation in suppressor modulated pentodes is to power the screen grid with a voltage dropping resistor from the plate supply rather than use an independent supply. While not available in power tubes, many receiving pentodes are designed such that the suppressor grid acts much like the grid in terms of its transconductance. The 6AS6 is probably the earliest example of such tubes. They make good mixers. 73, Barry WA4VZQ Thanks for your answer. A negative suppressor grid then tends to "isolate" the plate from the rest of the tube. So, the effect is similar to when, if the plate voltage of a power audio amplifier stage is removed by accident, the screen gets quickly destroyed due to excessive power dissipation. I shall then carefully check the screen dissipation in the suppressor-modulated transmitter I am planning to buld. Thanks and 73 Tony I0JX |
Suppressor-grid modulation
The aim was, guess what? Suppressor-grid modulation! I can remember
hearing some of these rigs on the air. I don't know just what percentage of modulation was possible, but I remember it being pretty weak. Good strong signal with very low modulation level. The aim had been to use what parts one had, and it surely was an inexpensive way to join the AM crowd! Old Chief Lynn, W7LTQ In the 1957 ARRL Handbook, these particular tubes were also used in a cathode driven (grounded grid) amplifier. 73, Barry WA4VZQ Yes, I was aware of the "modified 1625" but for linear amplifier usage. Now I know that they were also used for suppressor-grid modulated stages. But now a doubt come to my mind: the 1625 is a beam-power tube, not a pentode (actually it is an 807 with 12.6V filament). So, how could it work in suppressor-grid modulated stages? 73 Tony I0JX |
Suppressor-grid modulation
"Antonio Vernucci" wrote in message
... The aim was, guess what? Suppressor-grid modulation! I can remember hearing some of these rigs on the air. I don't know just what percentage of modulation was possible, but I remember it being pretty weak. Good strong signal with very low modulation level. The aim had been to use what parts one had, and it surely was an inexpensive way to join the AM crowd! Old Chief Lynn, W7LTQ In the 1957 ARRL Handbook, these particular tubes were also used in a cathode driven (grounded grid) amplifier. 73, Barry WA4VZQ Yes, I was aware of the "modified 1625" but for linear amplifier usage. Now I know that they were also used for suppressor-grid modulated stages. But now a doubt come to my mind: the 1625 is a beam-power tube, not a pentode (actually it is an 807 with 12.6V filament). So, how could it work in suppressor-grid modulated stages? 73 Tony I0JX Read Lynn's post again. He said the carrier was strong but the audio was quite weak. It is quite difficult to get over 95% modulation with a suppressor modulator. With beam power tubes, you get far less than this. Also you get lots of distortion because the beam forming plates do not linearly control plate current, so you have to lower the modulation level even further to make the audio readable by listeners. Hence the "strong signal with very low modulation level" makes sense. Fortunately with pentodes, it is easy to drive the output to zero (negative modulation). The real problem occurs when the suppressor is driven very far into the positive voltage region and it starts drawing current. Typically the suppressor grid can only dissipate a few watts. Since current is drawn during the positive peaks, an audio driver must present a low impedance. 73, Barry WA4VZQ |
Suppressor-grid modulation
Nordic Breeds WA4VZQ wrote:
Read Lynn's post again. He said the carrier was strong but the audio was quite weak. It is quite difficult to get over 95% modulation with a suppressor modulator. With beam power tubes, you get far less than this. Also you get lots of distortion because the beam forming plates do not linearly control plate current, so you have to lower the modulation level even further to make the audio readable by listeners. Hence the "strong signal with very low modulation level" makes sense. My experience was about 25% modulation, and that was with distortion that was... well... kind of bad. I would characterize this as pretty much the worst quality AM ever, worse than screen grid modulation by a long shot. Fortunately with pentodes, it is easy to drive the output to zero (negative modulation). The real problem occurs when the suppressor is driven very far into the positive voltage region and it starts drawing current. Typically the suppressor grid can only dissipate a few watts. Since current is drawn during the positive peaks, an audio driver must present a low impedance. And this also quickly becomes a distortion source unless the audio driver stage is pretty hefty. Just say no. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
Suppressor-grid modulation
Fortunately with
pentodes, it is easy to drive the output to zero (negative modulation). The real problem occurs when the suppressor is driven very far into the positive voltage region and it starts drawing current. Typically the suppressor grid can only dissipate a few watts. Since current is drawn during the positive peaks, an audio driver must present a low impedance. 73, Barry WA4VZQ Ah, yes, "(negative modulation)"! You seem to be "hep" on old stuff, do you remember "negative peak clipping"? I thought I was in Heaven in about 1958 with a single 2E26 final on 15 Meters. In class C, with a pair of 6L6 modulators, push-pull, class AB1, and used a VR tube across the modulation transformer secondary clipping the negative peaks, while allowing the positive peaks to go "over" 100%. Technical gurus of the day poo-poo'd the scheme. It looked a little rough on the scope, but unsolicited signal reports said it "packed a lot of modulation". I am thinking it must have been a little like more modern amateur "speech processing" I also seem to remember those modified 1646's getting almost 20% suppressor grid modulation after tinkering around with power supply voltages. Old Chief Lynn, W7LTQ |
Suppressor-grid modulation
"coffelt2" wrote in message
... Ah, yes, "(negative modulation)"! You seem to be "hep" on old stuff, do you remember "negative peak clipping"? I thought I was in Heaven in about 1958 with a single 2E26 final on 15 Meters. In class C, with a pair of 6L6 modulators, push-pull, class AB1, and used a VR tube across the modulation transformer secondary clipping the negative peaks, while allowing the positive peaks to go "over" 100%. Technical gurus of the day poo-poo'd the scheme. It looked a little rough on the scope, but unsolicited signal reports said it "packed a lot of modulation". I am thinking it must have been a little like more modern amateur "speech processing" I also seem to remember those modified 1646's getting almost 20% suppressor grid modulation after tinkering around with power supply voltages. Old Chief Lynn, W7LTQ Hi Lynn, A pair of 6L6's to modulate a 2E26... there was enough audio to drive a 6146 with a some to spare and enough to really overmodulate a 2E26! :-) Negative peak clipping was based on a diode with its anode connected to B+ and its cathode connected to the output side of the modulation transformer. This would allow the final's voltage to drop to only a few volts during negative modulation peaks. Later refinement was to add a gaseous voltage regulator tube between the diode's cathode and the output side of the transformer. In this case, the final's voltage would only drop to a voltage determined by the regulator tube. Today a silicon diode might be used, and zeners would replace the VR tube. The result of this circuit was that the RF would never be completely cut off during negative modulation peaks. Positive modulation peaks would be passed allowing higher positive modulation. This is what gave the higher "talk power." It still caused distortion, but much less than that if the negative peaks were not clipped. Everyone's voice is asymmetric. If you look at the voice waveform with an oscilloscope, you will see that peaks on one side of zero are often considerably higher that the opposite polarity. The average is still zero, however. The peak is caused by harmonics in the voice being in phase with each other. This property can be used to advantage in amplitude modulation by having the peaks occur on the positive modulation. Usually all that was needed to put the peak on the right side was to reverse the connections to the modulation transformer or to reverse the connections to the microphone. I am sure Scott Dorsey knows more about this than I do, but CBS produced two devices called the Audimax and Volumax that shifted the phase of the audio as a function of frequency. Another term for these devices is phase rotator. Kahn Communications also was in the market with its SymmetraPeak. To the ear, the sound was unchanged, but to the transmitter, the peaks became symmetrical. There is an excellent discussion of these devices on James Tonne's (W4ENE) website http://www.tonnesoftware.com/appnote...s/allpass.html and on Gary Blau's (W3AM) website http://www.w3am.com/8poleapf.html. {A biased opinion here — Jim's site contains some _excellent_ free software.} As to being "hep" on old technology, I appreciate the compliment. As an undergraduate, my university taught tubes and transistors. By the time I got to graduate school, tubes were no longer taught. By the time I got out of graduate school, integrated circuits were the "in thing" and microprocessors had just begun. I do have a good collection of older engineering books, however. I am constantly amazed by the technology of the late 1920's and the 1930's. And it was all designed without the benefit of computers! While I haven't used it in years, I still have my K&E metal log-log-decitrig slide rule, and the bamboo rule I used while in high school. 73, Barry WA4VZQ |
Suppressor-grid modulation
Nordic Breeds WA4VZQ wrote:
I am sure Scott Dorsey knows more about this than I do, but CBS produced two devices called the Audimax and Volumax that shifted the phase of the audio as a function of frequency. Another term for these devices is phase rotator. Kahn Communications also was in the market with its SymmetraPeak. To the ear, the sound was unchanged, but to the transmitter, the peaks became symmetrical. There is an excellent discussion of these devices on James Tonne's (W4ENE) website http://www.tonnesoftware.com/appnote...s/allpass.html and on Gary Blau's (W3AM) website http://www.w3am.com/8poleapf.html. {A biased opinion here — Jim's site contains some _excellent_ free software.} The original Audimax/Volumax combination had no phase rotator. I worked at an AM station that used them, and the chief engineer had installed a phase reverse switch on the announcer mike and auditioned each announcer to tell them which position to use. (Apparently they had used figure-8 mikes a year or so before I got there, and the announcers just used the front of back of the mikes). A lot of stations using the Audimax/Volumax would also have a phase rotator in the chain, though. CRL made a popular one, and so did Garron. Some folks made some boards tht dropped inside the Volumax for it too, but I never used any of those. I went to the Optimod as soon as I could, and it has a great phase rotator. The phase rotator is a hell of a great gadget, it gives you a lot of loudness without any perceived distortion. Mind you, for communications applications it's no more effective just than aggressive clipping, but there are folks who don't want aggressive clipping. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
Echoplex, was: Suppressor-grid modulation
"Scott Dorsey" wrote in message
... The original Audimax/Volumax combination had no phase rotator. I worked at an AM station that used them, and the chief engineer had installed a phase reverse switch on the announcer mike and auditioned each announcer to tell them which position to use. (Apparently they had used figure-8 mikes a year or so before I got there, and the announcers just used the front or back of the mikes). A lot of stations using the Audimax/Volumax would also have a phase rotator in the chain, though. CRL made a popular one, and so did Garron. Some folks made some boards that dropped inside the Volumax for it too, but I never used any of those. I went to the Optimod as soon as I could, and it has a great phase rotator. The phase rotator is a hell of a great gadget, it gives you a lot of loudness without any perceived distortion. Mind you, for communications applications it's no more effective just than aggressive clipping, but there are folks who don't want aggressive clipping. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." Thanks for the corrections, Scott. Aggressive clipping creates a ton of distortion unless the voice signal is split into several bands, each processed and filtered, and then combined. The phase rotator theoretically produces no amplitude distortion, and due to the way the human ear works, the shifting of the phases is not heard. I read once that the cochlea and its nerves perform physiologically something akin to a mathematician performing a Fourier analysis. I find it amazing that we process sound, for the most part, on the amplitude versus frequency information, and ignore the phase versus frequency information. With modern operational amplifiers, it is fairly simple to produce a good phase rotator using cascaded all-pass networks. I would hate to have to manufacture the original SymmetraPeak with its inductor-capacitor network lattices. Well, we are pretty far from the original subject, but I have enjoyed the discussion. However I do have a Boatanchor question. I remember seeing ads in QST in the 1960's for a device I think was called "Echoplex." It was supposedly used on commercial and military voice communications circuits. I never heard one of these in use by a ham, probably because their cost could buy several Collins S-Line stations. Doing a Google search brings up lots of echo-effects processors for guitars and such, but I found nothing for communication usage. Do any readers here remember the device and its manufacturer and how it worked? 73, Barry WA4VZQ |
Echoplex, was: Suppressor-grid modulation
Nordic Breeds WA4VZQ wrote:
Aggressive clipping creates a ton of distortion unless the voice signal is split into several bands, each processed and filtered, and then combined. The phase rotator theoretically produces no amplitude distortion, and due to the way the human ear works, the shifting of the phases is not heard. Right. I think for communications use, though, the ton of distortion can actually help intelligibility of consonants under bad conditions. Certainly it gives you a distinctive sound in a pileup. I remember seeing ads in QST in the 1960's for a device I think was called "Echoplex." It was supposedly used on commercial and military voice communications circuits. I never heard one of these in use by a ham, probably because their cost could buy several Collins S-Line stations. Doing a Google search brings up lots of echo-effects processors for guitars and such, but I found nothing for communication usage. Do any readers here remember the device and its manufacturer and how it worked? I have only heard of the echo-effect box. "Everything I use must have X in it, like sex and echoplex" says Lee Scratch Perry. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
Echoplex, was: Suppressor-grid modulation
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Echoplex, was: Suppressor-grid modulation
You are both right.
On a 1966 issue of QST magazine, I found the advertisement of "Echoplex" by Kahn Research Laboratories. It sold for more than 300$, which was not cheap at those times. As to Lincomplex, I remember a friend of mine working for Page Europe who told me having installed Lincomplex on HF transmitters in Africa. 73 Tony I0JX Rome Italy |
Echoplex, was: Suppressor-grid modulation
"Antonio Vernucci" wrote in message
... You are both right. On a 1966 issue of QST magazine, I found the advertisement of "Echoplex" by Kahn Research Laboratories. It sold for more than 300$, which was not cheap at those times. As to Lincomplex, I remember a friend of mine working for Page Europe who told me having installed Lincomplex on HF transmitters in Africa. 73 Tony I0JX Rome Italy Thank you, Tony. Somehow, I think you are talking about Leonard R. Kahn of Kahn Research Laboratories in Freeport, Long Island, NY, and not A. Q. Khan of Khan Research Laboratories in Kahuta, Pakistan (Pakistan's main nuclear weapons laboratory as well as an emerging center for long-range missile development). Leonard Kahn is best known for his paper: L.R. Kahn, “Single Sideband Transmission by Envelope Elimination and Restoration,” Proceedings of the IRE, Vol. 40, July 1952, pp. 803–806., and for his work on AM stereo. Google somehow doesn't know the difference... 73, Barry WA4VZQ |
Echoplex, was: Suppressor-grid modulation
"Nordic Breeds WA4VZQ" wrote in message ... "Antonio Vernucci" wrote in message ... You are both right. On a 1966 issue of QST magazine, I found the advertisement of "Echoplex" by Kahn Research Laboratories. It sold for more than 300$, which was not cheap at those times. As to Lincomplex, I remember a friend of mine working for Page Europe who told me having installed Lincomplex on HF transmitters in Africa. 73 Tony I0JX Rome Italy Thank you, Tony. Somehow, I think you are talking about Leonard R. Kahn of Kahn Research Laboratories in Freeport, Long Island, NY, and not A. Q. Khan of Khan Research Laboratories in Kahuta, Pakistan (Pakistan's main nuclear weapons laboratory as well as an emerging center for long-range missile development). Leonard Kahn is best known for his paper: L.R. Kahn, “Single Sideband Transmission by Envelope Elimination and Restoration,” Proceedings of the IRE, Vol. 40, July 1952, pp. 803–806., and for his work on AM stereo. Google somehow doesn't know the difference... 73, Barry WA4VZQ Wow, isn't this a super thread? Learned more here in a week of spare time than 60 years of experiments and reading magazines! Where was Usenet when we needed it? Old Chief Lynn, W7LTQ |
Echoplex, was: Suppressor-grid modulation
Somehow, I think you are talking about Leonard R. Kahn of Kahn Research
Laboratories in Freeport, Long Island, NY, and not A. Q. Khan of Khan Research Laboratories in Kahuta, Pakistan (Pakistan's main nuclear weapons laboratory as well as an emerging center for long-range missile development). Leonard Kahn is best known for his paper: L.R. Kahn, “Single Sideband Transmission by Envelope Elimination and Restoration,” Proceedings of the IRE, Vol. 40, July 1952, pp. 803–806., and for his work on AM stereo. Google somehow doesn't know the difference... Yes, it was Leonard Kahn. I have an Kahn SSB adapter for 455-KHz IF receivers. It employs a great deal of nuvistors. Very complex machine! 73 Tony I0JX |
Suppressor-grid modulation
Antonio Vernucci wrote:
I am planning to build a suppressor-grid modulated AM transmitter. In all the diagrams I have seen they use proper pentodes, i.e. tubes that have a real suppressor grid (e.g. 803). I have seen no diagram using beam power tubes (e.g. 813 or 814) which have beam forming plates instead of the suppressor grid . Before purchasing 803 tubes, I would like to be sure that 813s or 814s are really unsuitable for suppressor-grid modulation. My question is whether, with 813s or 814s, the plate current can be actually controlled by varying the beam forming plates voltage. Does anyone have experience on that issue? 73 Tony I0JX Rome, Italy A little late, but could be of interest: Try the 2E22 valve. I used to work with this excellent valve during my military service in 1968, repairing military equipment that used it as supresor modulated. It was built especially for that purpose. Here are the specifications: 2E22 Power Pentode Base & Bulb EIA Base 5J Mechanical Data EIA Base ...................................... 5J Electrical Data Heater Voltage ................................ 6.3 V Heater Current ................................ 1.5 A Direct Interelectrode Capacitances (approx) Pentode Input ......................................... 13 pf Output ........................................ 8 pf Grid to Plate ................................. 0.2 pf Maximum Ratings (Design Center Values) Pentode Plate Voltage ................................. 750 V Grid No. 2 Voltage ............................ 250 V Plate Dissipation ............................. 30 W Grid No. 2 Dissipation ........................ 10 W Characteristics and Typical Operation Class C Oscillator/Amplifier Plate Voltage ................................. 750 V Grid No. 3 Voltage ............................ 22.5 V Grid No. 2 Voltage ............................ 250 V Grid No. 1 Voltage ............................ -60 V Grid No. 1 Current ............................ 6 mA Plate Current ................................. 100 mA Grid No. 2 Current ............................ 16 mA Driving Power ................................. 0.55 W Power Output (approx) ......................... 53 W Characteristics and Typical Operation Class C Modulated Amplifier (Supressor) Plate Voltage ................................. 750 V Grid No. 3 Voltage ............................ -90 V Grid No. 2 Voltage ............................ 250 V Grid No. 1 Voltage ............................ -90 V Plate Current ................................. 55 mA Grid No. 2 Current ............................ 29 mA Power Output (approx) ......................... 16.25 W Alejandro Lieber LU1FCR Rosario - Argentina Real-Time F2-Layer Critical Frequency Map foF2 at: http://1fcr.com.ar |
Suppressor-grid modulation
Try the 2E22 valve.
I used to work with this excellent valve during my military service in 1968, repairing military equipment that used it as supresor modulated. Thanks for suggestion. I have some 2E22s, even some 2E24s (quick.heating versions). The problem with the 2E22 is that the output power would be small (probably 10W or so) because, using suppressor screen modulation, the efficiency is rather low (30%). Using two 803s I can instead get 200W or perhaps 250W of carrier. 73 Tony I0JX |
Suppressor-grid modulation
"Antonio Vernucci" wrote in message
. .. Thanks for suggestion. I have some 2E22s, even some 2E24s (quick.heating versions). The problem with the 2E22 is that the output power would be small (probably 10W or so) because, using suppressor screen modulation, the efficiency is rather low (30%). Using two 803s I can instead get 200W or perhaps 250W of carrier. 73 Tony I0JX Hi Tony, The 2E22 is a true pentode while the 2E24 is a quick heating filament version of the 2E26. Both are beam power tetrodes and not suitable for suppressor modulation. A pair of suppressor modulated 803's will deliver approximately 100 watts of carrier. 73, Barry WA4VZQ |
Suppressor-grid modulation
Hi Tony,
The 2E22 is a true pentode while the 2E24 is a quick heating filament version of the 2E26. Both are beam power tetrodes and not suitable for suppressor modulation. A pair of suppressor modulated 803's will deliver approximately 100 watts of carrier. 73, Barry WA4VZQ Hello, Barry is right ! With 2 x 803, input power will be as far as 1,5 x 2 x 125 W = 375 W and carrier power, about 125 W (33% of 375) only. No more ! All the best Jean-Pierre (F6BGV) |
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