After careful examination, I have found my 73kHz fault. It was not the Tx
FETs, but an insulation breakdown in the wire that takes the RF through the
house wall. It is well insulated and goes through plastic conduit, but
testing it with the 136kHz Tx in the dark produced a warm glow at the end of
the piping and a hissing noise. The insulation on the wire had broken down -
probably the gradual deterioration caused by corona on 73kHz - and the
plastic conduit was not man enough for the job. It must have caused a
complete short circuit with the higher voltages on 73k. I think I will have
to try my local car spares dealer to see if I can buy some ignition wire.
I am now available for skeds or test transmissions on 73kHz is anyone wants
one.
Mike, G3XDV
http://www.lf.thersgb.net
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