Friday, November 11, 2011

Not so chirpy

Yesterday I attempted to have a QSO using the XBM-10-2 two transistor "Chirpy" transceiver for 10m. I asked Jim, G3XPD, who is about 8km south of G4ILO to listen out for me. Jim could hear the distinctive sound of my 100mW transmission, but I could not hear Jim, not even when he called using 100W.

I know the Chirpy receiver works because I can receive a locally generated signal such as my antenna analyzer. But I guess even that is a big signal compared to one received off the air. I need to find a way to improve the receive sensitivity if it is to be possible to make a real two-way contact using this simple transceiver circuit.

I have tried adjusting C2 for maximum noise in the earpiece rather than maximum output when the key is down, to see if that gives some improvement. If nothing else it seems to have tamed the chirp a bit.
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