CW PRACTICE/TX MONITOR
by Harry Lythall - SM0VPO

Here is a little novelty circuit that I found in some time ago, dug out of the archives after an E-mail request. The circuit was given to me by the late G8ABZ in about 1967 as a circuit that will oscillate first-time every-time. I have added a diode detector so that it will generate a sound when a transmitter is keyed.

The input only needs to be placed near the transmitter to pick up enough RF to cause it to squeek. With QRP rigs some additional coupling or circuitry may be necessary. The 1.5 volt battery and key can of course be used for CW practice using the same circuit.

The transistor may be almost any PNP small signal germanium transistor, for example: 'RED SPOT', OC44, OC45, OC71, OC72, OC81, AF114, AF117, AC126, AC127, AC128 ... etc. Very old transistor radios used to use those crappy germanium transistors begining with '2SB...' which also work very well. The transformer is the RED output transformer robbed from one of those cheap'n-nasty transistor radios.

Have fun, de HARRY, Lunda, Sweden.

Dont forget to visit my messageboard if you have any questions about this or any other project. I always look forward to receiving feedback, positive or negative. You do not have to register to post messages.

Very best regards from Harry Lythall
SM0VPO (QRA = JO89WO), Märsta, Sweden.
EA/SM0VPO (QRA = IM86BS), Nerja, Spain.

Return to INFO page