K4SB mentioned my interface box, so I'll go ahead and describe
what it does. It is an evolving project, so don't ask for the
exact circuit to copy! This is "food for thought."
Inputs to the box are:
1. Parallel cable from LPT1
2. TX control and +12V from my two ICOM 765s
3. Headphone audio from the radios
4. External keyer
I installed eight SPDT and DPDT relays. Four are presently in use
with the others available for expansion. The keying line and A/B
radio lines go to NPN transistor switches that are wired to the
desired relays. I don't use the PTT line at this time.
Switching functions presently used are:
1. Computer + external keyer switched to radios A/B
2. Front-panel LEDs to show which radio is active
3. Switched +12V for external A/B accessories -- presently just a
separate switch box to route the rigs to one amp for single-band,
dual-receive operation.
4. Audio mix during transmit -- A/B/Split selection is manual, but I
have the option of mixing the audio from two radios when transmitting.
It's nice to emphasize one radio while the other is transmitting, but
I also like to hear the sidetone from the other radio.
5. Audio from the active radio is switched for sound card recording
on one channel.
As I said, this is an evolving project. I have a few other things to
try out, plus I've only tried to accommodate CW so far. As complicated
as it sounds, each function is fairly simple to implement. Having all
the control lines come into one box avoids a "rats nest" behind the
radios.
My bottom line: Station automation is essential for maximum operating
efficiency. The reduction in fatigue alone is worth the effort.
Gary, K9AY
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