Similar problems here in the past- on a specific band with a certain antenna
located near
the house, my LPT keying interface would latch on, and stay on, until I would
kill the
transmitter power. Miniature axial leaded chokes (100uH) cured the problem. I
put one in
series with the collector of each transistor in the interface (the CW key line
and PTT
lines). Without the chokes, the key line would go negative by a few volts DC
from the
rectified RF, and stay there, keying the transceiver, until I turned its
transmit power
off.
Shielded cables would not work. (Currents flowing on the shield will still
induce an RF
voltage in the conductors inside it.)
Capacitors did not work too well for me either. But the chokes made a rock
solid cure.
Maybe CT only toggles one of the pins to the transistor's base and emitter, and
other
software does it differently, don't know, but that might explain the other
mystery.
GL,
Chet, N8RA
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