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łTwin Triode˛ transmitter background information
For the better part of twenty years I have been hearing comments that the original source of the łTwin Triode˛ transmitter design was a construction article that had been published in Electronics Australia magazine. A reader of this group recently sent me a copy of the Electronics Australia article, which was written by Peter Lankshear. I have extracted the original schematic from Peter's article and posted it here for discussion. http://fmamradios.com/stuff/mate%20TX%20schematic.gif Some points worth noting, the High Voltage power supply is 250 volts, somewhat higher than the approximately 160 volts used in the łTwin Triode˛ transmitter. The oscillator, under carrier conditions, operates with a plate voltage of 100 volts, and a plate current of 2.95 mA, for a DC power input to the final RF stage of 295 mW, somewhat above the 100 mW limit that is allowed in the USA. The Electronics Australia transmitter also includes an audio pre amp stage like Flipper added to his, making it a łTriple Triode˛ transmitter. Also, as Flipper suggested, it uses a 470 pF RF bypass capacitor from the modulator plate to ground, rather than the 10,000 pF capacitor the ASCII schematic version used. This reduces high frequency slewing distortion as Flipper has reported. The Electronics Australia transmitter also has the oscillator grid capacitor connected to the oscillator cathode for DC as I suggested, so that the capacitor doesn't have the full modulator plate audio signal impressed across it, further reducing high frequency slewing distortion. V1 the audio preamp can be either a 6AV6 or 6AT6, and V2 the modulator & oscillator can be either a 12AU7, 12BH7, or 6CG7, according to Peter's article. -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
#2
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Quote:
Now that a succesful couple of circuits have been proposed do you intend to build your own? Cheers, John |
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