630/160/80/40 Meter Cw Qrp Battery Powered Ham Radio Receiver/ Transmitter

  

This item has exposed high voltage underneath the chassis. The radio you receive will look very similar to the photos.

The large tuning dials may vary in appearance, depending on what I have in stock. Also, it is becoming quite difficult to keep the brass plate capacitors in stock, to the radio you receive may be of the standard gray plate variety. The circuit has a battery powered dc to ac inverter, and the no load dc voltage underneath the hood is over 300 volts!

So even though the power source comes from harmless low voltage batteries it can still be lethal if not handled responsibly. 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 require 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). 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 630 and 160 meters is about 3.4 watts. About 2.4 watts on 80 and around 1.4 watts on 40 meters.

Power out on these old audio tubes drops off considerably as you go up in frequency, so on 30 meters I'm only able to get around 250 to 300 milliwatts RF output. I'll provide one each, QRP HC49 crystal types, for 80, 40 and 30 meter cw, but I have no spares for 160 meters. You'll need to supply a crystal for that band. I will also include one crystal for the 630 meter band, but with low power, unless you have a really good antenna, you'll be lucky to transmit across the county line. Plug-in coils are provided for the bands mentioned. Then, from about 1650 khz to 12.5 mhz, by changing the coils.

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.