15 Feb 2013

OXO on 14MHz

An OXO transmitter on 14MHz
This afternoon I decided to build a 14MHz OXO transmitter. As is often the case, I like to re-use old boxes and project parts, so the FETer box was photographed for posterity, then gutting and used for the OXO transmitter. In this version I did not go for full break-in and instead used a simple changeover switch, but added a push button net function to allow me to net the VXO without the PA being keyed. A small toroid in series with the crystal allows about 15kHz VXO range around the 14.060MHz QRP frequency. I used a 2N3904 for the oscillator and 2N3906 for the keying transistor and a 2N3866 for the PA, but may change this for 4  x 2N3904s in parallel for lower cost. My output is a little low at around 500mW.

It works fine with reverse beacon reports from Iceland and Slovenia and a nice 2-way QRP QSO with IK2RGV who was running 5W.

The OXO really is a classic circuit: you just build it and it works.  Another version is on the QRPkits page.

1 comment:

Anonymous said...

Great fun Roger

Seems to work every time with most ready available
transistors like the BCY 71, BFY51 and BC109 .Can be built in 20 minutes.