"N2EY" wrote


Have to build an interface to key the Southgate Type 7, though. Nice old CP
Clare mercury wetted relay should do the job...


How much voltage on the keying line? Unless it's grid-block keying or similar,
you won't need a relay.

Serial port keying (assuming the radio is positive keyed) can be built into a
DB25 or DB9 connector shell using only a single resistor and a junk-box
transistor.

Hang a 1K resistor on DTR (pin 20 on a DB25, pin 4 on a DB9). Other end of the
resistor to the base of a small-signal NPN (I use a 2N3904 cuz it was in my junk
box, but 2N4401 or others similar will be just fine). Connect the emitter and
the transmitter ground return to Signal Ground (pin 7 on a DB25, pin 5 on a
DB9). Connect the collector directly to the transceiver key input.

73, de Hans, K0HB