Since about 1985 most icom radios have pin 8 of the microphone connector
wired to the speaker. This is convenient for the wiring of a tnc
and is usually easy to modify so that receive audio is taken from
the high side of the volume control.
On the ic-27/37/47 radios, on the bottom side of the radio, since
about 1985 most icom radios have pin 8 of the microphone connector
wired to the speaker. This is convenient for the wiring of a tnc
and is usually easy to modify so that receive audio is taken from
the high side of the volume control.
On the IC-27/37/47 Radios, on the bottom side of the radio, just under
the area of the speaker, is a two pin connector with a green and red
wire attached. The green wire is speaker audio and the red wire is +8 volts.
By cutting these wires and attaching the green wire to the high side of
the volume control and atted wire to switched 12 volts.
A TNC can be wired to just the microphone connector and makes a clean
installation provided the radio is dedicated to packet.
To get back to the subject of the alternate modification for the ic-3200a
you can rewire pin 8 of the microphone connector to the high side of the
volume control and avoid the muting circuit but if you plan to leave
the tnc wired permenantly to the radio and also,to use the radio on voice
you will need to change a resistor in the tnc so as not to load down the
audio at the volume control. The value of this resistor will have to
be determined experimentaly.
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