26/Feb/2005

I have recently been given a modern laptop that I occasionally use together with
my ICOM IC706MKiiG for listening to narrowbandwidth modes such as QRSS.

Once I wanted to operate in PSK31 and I realised the laptop was lacking the serial
port, that is needed to simulate the PTT when transmitting. I already knew that
VOX did not work when the audio was injected through the ACC1 port, but it does
work with a normal microphone.

There comes the idea: connect my digimode PC/radio interface to the microphone socket
rather than the accessory socket.

Altought the 706 MIC cord looks weird, it uses a standard computer LAN plug/socket!
Nothing easier to replicate! Moreover it has both MIC and AF lines.

I got hold of a "patch", that is a short cable for connecting PC network cards to
the neighbouring plug. A patch is usually 1 or 2m long and has connectors on both ends.
I cut it in half and identified wire colours that matched IC706 mic plug layout.
I needed to identify 4 wires: ground, microphone, audio frequency and PTT (which I
wired for future uses).

The microphone plug layout is described on the IC706 manual.

Once I mapped colors to functions I wired them to my "standardized" plug for PC<->radio
interface and the job was done! Less than 5 minutes of looking, peeling and soldering.


On the other hand it took a while to figure out that the AF output level in the
microphone plug is controlled by the volume knob. In the beginning I tought that the
laptop was decoding what was coming through the air in the room, from the 706 loudspeaker.
Then I plugged a pair of headphones in the RTX and realised that the volume controls
both levels.


Good luck with your wiring and, of course, I take no responsibility to any damage
you might cause to any animated and/or inanimated object.

Paolo

PS: a patch can be bought in any shop that sells computer stuff, or you might get one
for free from your office IT department, if you're lucky.

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