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
Select LSB and turn DATA ON. Check the DATA indicator, COMP OFF. External PTT mutes the microphone, but microphone PTT enables it; disconnect the microphone. No USB audio input setting.
| Item | Setting / check |
|---|---|
| Mode | Select LSB and turn DATA ON. Check the DATA indicator, COMP OFF. External PTT mutes the microphone, but microphone PTT enables it; disconnect the microphone. No USB audio input setting. |
| ACC(1) (8-pin) pin 4 MOD | Interface TX audio → ACC(1) (8-pin) pin 4 MOD. |
| ACC(1) (8-pin) pin 5 AF | ACC(1) (8-pin) pin 5 AF → interface RX input. Normally independent of the AF knob. |
| ACC(1) (8-pin) pin 2 GND | Connect pin 2 GND as specified by the audio interface. |
| ACC(1) pin 3 SEND | Compatible PTT interface grounds pin 3 SEND to transmit. A CI-V cable alone cannot operate this PTT line. |
| CI-V Address | Default 2Ch. 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 level | Start 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.
Serial keying for TX; Audio IN for RX. Neither primary nor secondary Audio OUT is used. Check radio RTTY mode, 170 Hz shift and Mark frequency. Keying polarity is independent of RX inversion.
The manufacturer manual uses the ACC RTTY keying input for FSK. A separate serial port and a suitable FSK interface are required. A USB socket does not mean FSK is available with only a USB cable. Never connect RS-232 signals directly to ACC.
Radio settings
| Radio item / connection | Setting / matching |
|---|---|
| FSK input / keying | ACC (1): RTTY / FSK |
| Serial connection | Use a separate FSK COM port from CAT for this model. Check the connection and avoid PTT signal conflicts. |
| Operating mode | RTTY |
| RTTY shift | 170 Hz |
| RTTY Mark frequency | 2125 Hz |
| PTT (TX/RX switching) | Do not assign the same line to PTT and FSK |
| Audio IN | Use the usual receive audio input |
The manufacturer manual uses the ACC RTTY keying input for FSK. A separate serial port and a suitable FSK interface are required. A USB socket does not mean FSK is available with only a USB cable. Never connect RS-232 signals directly to ACC. With external control set to radio PTT, a dedicated FSK COM can share different lines, for example FSK=DTR and PTT=RTS. Keep this port separate from CAT and never assign both functions to one line. This older model uses RTTY only. Check radio settings for shift, Mark frequency and polarity. Receive inversion and FSK output inversion are separate.
Keying polarity mapping
| PSRTTY inversion | DTR OFF | DTR ON |
|---|---|---|
| Not inverted | Mark | Space |
| Inverted | Space | Mark |
This table maps PSRTTY control signals. It is independent of A/B selection and RX decoding inversion. Start without inversion, then match the radio/interface polarity.
If FT8 already works
If FT8 works through the same ACC audio, keep wiring/gain and change USB to LSB. Check DATA ON and retain external PTT.
PSRTTY settings · AFSK
Select IC-765, CI-V COM and explicit external Audio IN/OUT. Automatic mode switching on connection OFF; set the radio mode described above. Select external PTT and match interface COM, RTS/DTR and polarity. Close apps using the same COM.
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.