Connection
Connect rear REMOTE (CI-V) to the PC using a compatible CI-V interface. Connect external sound hardware/radio interface to ACC (13-pin). A USB CI-V cable alone carries no audio. TX: PC output → MOD; RX: AF → PC input.
Radio settings · AFSK
Select plain LSB on the radio and disconnect the microphone. Turn COMP OFF if fitted. There is no LSB-D or USB audio input switching. Native RTTY is FSK, not PSRTTY AFSK.
| Item | Setting / check |
|---|---|
| Mode | Select plain LSB on the radio and disconnect the microphone. Turn COMP OFF if fitted. There is no LSB-D or USB audio input switching. Native RTTY is FSK, not PSRTTY AFSK. |
| ACC (13-pin) pin 11 MOD | Interface TX audio → ACC (13-pin) pin 11 MOD. |
| ACC (13-pin) pin 12 AF | ACC (13-pin) pin 12 AF → interface RX input. Normally independent of the AF knob. |
| ACC (13-pin) pin 2 GND | Connect pin 2 GND as specified by the audio interface. |
| ACC pin 3 SEND / pin 7 VSEND (MkII / MkIIG) | Original IC-706: pin 3 SEND for all bands, pin 7 NC. MkII: pin 3 HSEND HF/50 MHz, pin 7 VSEND 144 MHz. MkIIG VSEND SEL: on = pin 3 HF/50, pin 7 144/430; U only = pin 3 HF/50/144, pin 7 430; oFF = pin 3 all bands. A compatible PTT circuit grounds the matching SEND. Match cable wiring to the band. |
| CI-V Address | Default IC-706: 48h / MkII: 4Eh / MkIIG: 58h. Match PSRTTY to the radio’s actual CI-V address. |
| CI-V Baud Rate | Match CI-V Baud Rate and PC speed. |
| 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.
IC-706
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 (13-pin): 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-R |
| 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.
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.
Manufacturer reference: manual / USB port settings (IC-706)
IC-706MkII
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 (13-pin): 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-R |
| 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.
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.
Manufacturer reference: manual / USB port settings (IC-706MkII)
IC-706MkIIG
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 (13-pin): 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-R |
| 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.
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.
Manufacturer reference: manual / USB port settings (IC-706MkIIG)
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
- IC-706 official manual, p.6 — Icom
- IC-706MkII official manual, p.6 — Icom
- IC-706MkIIG official manual, p.6 / VSEND SEL — Icom
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.