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PSRTTY · Radio setup guides

IC-725

PSRTTY AFSK guide for IC-725 with an external audio interface. The radio has no built-in USB audio. Keep working FT8 audio wiring and check CAT and audio separately.

Checked: 2026-10-14

Connection

Connect rear REMOTE (CI-V) to the PC using a compatible CI-V interface. Connect external sound hardware/radio interface to ACC(1) (8-pin). A USB CI-V cable alone carries no audio. TX: PC output → MOD; RX: AF → PC input.

Radio settings · AFSK

Use plain LSB for AFSK. No LSB-D or USB audio input switching. Disconnect the microphone, turn COMP OFF if fitted and check external ACC(1) audio.

ItemSetting / check
ModeUse plain LSB for AFSK. No LSB-D or USB audio input switching. Disconnect the microphone, turn COMP OFF if fitted and check external ACC(1) audio.
ACC(1) (8-pin) pin 4 MODInterface TX audio → ACC(1) (8-pin) pin 4 MOD.
ACC(1) (8-pin) pin 5 AFACC(1) (8-pin) pin 5 AF → interface RX input. Normally independent of the AF knob.
ACC(1) (8-pin) pin 2 GNDConnect pin 2 GND as specified by the audio interface.
ACC(1) pin 3 SENDCompatible PTT interface grounds pin 3 SEND to transmit. A CI-V cable alone cannot operate this PTT line.
CI-V AddressDefault 28h. Match PSRTTY to the radio’s actual CI-V address.
CI-V baud (PC)Standard: 1200 bps. If FT8 CAT works, use that baud rate in PSRTTY. On these older models the setting is internal, not a front-panel menu item.
Audio TX levelStart with low PC/interface/PSRTTY TX volume. There is no USB MOD Level setting on the radio.

FSK keying transmission · Ver1.18

Example: DTR for FSK and CI-V/CAT for PTT. Adjust settings to your wiring and selected signals.

The manufacturer manual specifies AFSK operation for this model. Native direct FSK keying is not supported; use normal AFSK mode.

Manufacturer reference: manual / USB port settings (IC-725)

If FT8 already works

If FT8 works in plain USB through the same external audio device, keep wiring/gain first, switch the radio to LSB and test RTTY. Do not switch to LSB-D.

PSRTTY settings · AFSK

In PSRTTY 1.16 select external PTT and match the compatible interface COM, RTS/DTR and polarity. CI-V CAT, audio and PTT are separate paths. Automatic mode switching on connection OFF; select plain LSB on the radio. Choose explicit external Audio IN/OUT and the exact radio model.

No modulation

Compare FT8/PSRTTY output devices → check radio mode → TX audio to MOD and RX audio from AF → interface levels. If CAT works but no modulation, check audio cable and Audio OUT first.

Official sources

Based on official manuals for each model. Check pin numbers in the rear-view diagram. For generation or regional differences, follow the manual for your radio.