This is a vacuum tube ham radio QRP cw transmitter and regen radio. The circuit uses two (2) 12A6GT tubes, one for the regenerative receiver and one for the cw transmitter.
The 12A6 transmitter tube requires only 0.15 amps drain from the power source and since a 12L6, 12V6 or 12W6 tube requires considerably more amps for the filament and produced only about a 5% gain in power out, I decided to just go with the 12A6 tubes for this radio. So while you can get slightly more power out with a 12V6 tube for transmit, the constant battery drain for the filament is more than 200ma greater than required for a 12A6. The inverter, which powers only the transmitter tube, turns off instantly when switched to receive mode. So it is not working at all when in the regenerative receive mode. The chassis requires an external 12 volt power source. I like to use a small motorcycle or golf cart battery, but so much the better if you have an old car battery that you are not using.This powers the filaments and inverter when in transmit mode. On the chassis a 9 volt rechargeable battery is required for the receiver, which is connected in series with the incoming 12 volt source, providing about 20 volts or so to run the regen detector.
The receiver requires high impedance 2 to 4k ohm inductive or piezo headphones, NOT INCLUDED in this listing. You may use a well filtered 12 volt bench supply to run this radio.
It should be capable of about 2.5 amps in transmit mode. For this circuit there's only a few ma drain on the 9 volt battery, so it will go for many hours if not days before needing to be recharged. The QRP transmitter output on 40 meters is about 1.5 watts. Power out on these old audio tubes drops off considerably as you go up in frequency.
On another listing I have this radio in a multi-band version, and power out for 160 and 80 meters is almost double that attained on 40. For this listing you will receive one plug-in coil and one QRP HC49 crystal for 40 meter cw, mounted in a FT-243 style holder. Frequencies available are 7030, 7040, 7055, 7110 and 7118 khz.
Please let me know if you have a preference. The dc inverter circuit employs a pair of TIP41C power transistors, working with a 6-0-6 volt 5 watt transformer that has a secondary winding of 220 volts.
The output is then rectified by a 1N4007 diode, then filtered, for well over 300 volts dc, no load. I will include a hand-sketched wiring diagram of this item, plus a sketch of all control panel functions. The controls are receiver main tuning, fine tuning, receive antenna coupling and regenerative action/power on/off switch.The transmitter has a single control for power out, with link coupling to the antenna. There's a single send/receive switch which controls all necessary functions, including high voltage power on for transmit and switching the antenna. So you only need a single antenna for send/receive.
In send mode the audio output will automatically be muted. AGAIN, EVEN THOUGH POWERED BY BATTERIES, IT CAN BE QUITE LETHAL IF NOT HANDLED WITH RESPECT! This is a given for most any ham radio transmitter. Schematics are available for most of my radios, which you can find on my other listings.