Quote from Don Rosberg on October 25, 2025, 11:27 am

Hi Paul, this might help. Just search results...

you can do true FSK on the IC-756PROII from the rear ACC(1) 8-pin DIN. Here’s the exact ACC(1) pinout from the Icom manual (the diagram there is “rear panel view” so the numbering/orientation matches what you see on the radio): qrzcq.com

• Pin 1 — RTTY (FSK keying input). Logic “LOW” < 0.6 V, “HIGH” > 2.4 V, input current < 2 mA.

• Pin 2 — GND.

• Pin 3 — SEND (PTT). Ground to transmit; input current (Tx) < 200 mA.

• Pin 4 — MOD (AF modulator input), ~100 mVrms, 10 kΩ (use this only for AFSK/voice).

• Pin 5 — AF (fixed level RX audio out), 100–300 mVrms, 4.7 kΩ.

• Pin 6 — SQLS (squelch output).

• Pin 7 — +13.8 V (max 1 A, for accessories—don’t short).

• Pin 8 — ALC in. qrzcq.com

How to wire it to a RIGblaster Pro (true FSK)

• RIGblaster Pro “FSK OUT” → ACC(1) Pin 1 (RTTY).

• RIGblaster Ground → ACC(1) Pin 2 (GND).

• Optional PTT: RIGblaster PTT (open-collector to ground) → ACC(1) Pin 3 (SEND).

• Receive audio to your sound card: ACC(1) Pin 5 (AF fixed) → PC Line-In (tip), sleeve to GND.

• Do not use Pin 4 (MOD) for FSK; that’s for AFSK/voice. For pure FSK RTTY, key only Pin 1. qrzcq.com

If you’d rather buy than build, West Mountain’s ready-made “Fixed Level Audio + FSK for ICOM DIN-8” cable does exactly this: it breaks out fixed-level RX audio and a 3.5 mm FSK plug that goes to the RIGblaster’s FSK output. It’s sold as their ICOM DIN-8 FSK/Audio cable (often listed as p/n 58129-994). westmountainradio.com+1

Build notes

• The radio uses the standard 270° 8-pin DIN male plug on the cable side.

• Keep the FSK lead short and shielded; tie shield to Pin 2.

• Logic from the RIGblaster is typically open-collector to ground, which the IC-756PROII expects on the RTTY input (Pin 1).

• In the radio, select RTTY mode with “FSK” (not AFSK) so it keys from Pin 1. (See the PROII user manual for RTTY setup.)

Quote from paul mackinnon on October 25, 2025, 1:49 pm

thanks