
The OXO QRP HF transmitter is a simple, low-power CW (continuous wave) transmitter designed by George Burt, GM3OXX. It is a single-band transmitter that can be built to operate on any of the amateur radio bands from 160 to 20 meters. The transmitter is built around a few standard transistors and a crystal oscillator. It is an elementary circuit to build, and can be assembled from a kit or from scratch.
The OXO transmitter is a QRP transmitter, which means that it produces a very low output power. This makes it ideal for making short-range contacts with other amateur radio operators. The OXO transmitter can also be used for experimentation and learning about radio electronics.
The OXO transmitter was originally described by George Burt (GM3OXX) in Sprat magazine in 1979 and has proved to be a very popular transmitter on its own and as a basis for other rigs. It can be built cheaply for any HF band by simply changing the crystal. Please note that an output Pi filter is required and which is not shown in the circuit diagram. The oscillator Q1 is general purpose 2N3904. The PA is any suitable RF output transistor, e.g . 2N3866, 2N4427, even a SL100 or 2N2219. The keying switch is 2N3904.

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