Interfacing ICOM IC-751

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1

This ICOM offers accessory connector with all necessary signals present:

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To interface Digirig we’ll need to homebrew an audio cable:

pin 3 → 3.5mm TRRS ring2 (RIG_PTT)
pin 4 → 3.5mm TRRS tip (RIG_AFOUT)
pin 5 → 20K resistor → 3.5mm TRRS ring1 (RIG_AFIN)
pin 8 → 3.5mm TRRS sleeve (GND)

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The resistor is suggested in this page as a way to allow the regular mic to continue functioning while digital modes interface is connected.

1 Like
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I 3D-printed the plug for the 24-pin connector on the back of a recently purchased IC-751A and pinned it as shown, but it doesn’t seem to be working. Questions are:

  • Should the audio from the rig still be working (as mine is) with the DigiRig connected, or should it be muted?
  • Does the DigiRig work with CAT control, or should I just use one or the other?
    Thanks in advance!
3

With accessory connections, typically radio’s speaker is not muted unless there is a dedicated signal for that and it’s activated.

Digirig does support serial CAT control, but the serial connections are not provided in the above pinout. For testing use audio and PTT without activating serial CAT functionality in the software.

4

just to further Denis’ response.

the IC-751 does support CI-V:
CT-17 CI-V Level Converter (requires UX-14).

but you have to have the UX-14 option installed.
your rig might have it from the previous owner.

the RX audio from the ACC port is fixed level and unmuted.
so you can just turn the volume knob down on the radio and it will not effect the audio level/volume going into the digirig/pc setup.

i setup an IC-730 (same generation and ACC jack) for psk31 before giving to another ham.

good luck
:slight_smile:
kb0wlf

5

Thanks for the responses. I have the Piexx UX-14(PX) installed, as well as their NVRAM upgrade, from the previous owner. I have another DigiRig Mobile connected to a Baofeng 2M HT that is working fine as a packet digipeater, but this is my first foray into HF.