[Amps] Amplifier Solid State Keying Relay Circuit

[Robert Carroll]

I recently started using my old backup radio, a FT1000MP which I have owned
for many years.  The main rig was out for repair.  I normally drive an Alpha
86 or 89 with QSK pin diode switching.  After scratching my head a while, I
remembered the QSK from the MP is via a back band data jack. I hooked it up
to the MP and it works very well.

 

The main rig arrived back from the hospital today and the MP, for the
moment, will be relegated to keying non-QSK rigs with conventional "keying"
relays.  While the MP has an internal relay which will handle this, enabling
it requires getting to a small slot on the back and sliding a PCB switch-not
nice when swapping back and forth between the Alphas and non-QSK amps-and
that little slide switch would be very inconvenient to replace if it becomes
flaky.  

Instead I would like to use the logic-level QSK signal from the MP band data
connector to key a sold state (BJT, FET, or opto-transistor) circuit which
would handle a conventional amplifier relay input-sort of like an external
relay circuit you use with an old amplifier with a 110VAC relay, but solid
state.

 

I have seen very simple circuits for such devices on the web, and there are
a couple of fairly inexpensive commercial ones available.  I can't seem to
locate any schematics for homebrewing one at the moment.  Though I have the
basic circuit ideas in mind, I would rather build something already known to
work well.  Can someone point me to such a unit?  I don't think any of the
relays I would need to key exceed about 24 volts dc at perhaps 100 mA.

 

73

Bob W2WG