Connection
Connect rear REMOTE (CI-V) to the PC using a compatible CI-V interface. Connect external sound hardware/radio interface to ACC1-A. A USB CI-V cable alone carries no audio. TX: PC output → MOD; RX: AF → PC input.
Radio settings · AFSK
Audio: SET [F-7] → ACC [F-2]; CI-V/RS-232C: SET → OTHERS. This guide uses analog audio via ACC1-A. Check DATA1 MOD = ACC-A; the USB memory port is not USB audio input.
| Item | Setting / check |
|---|---|
| Mode | Select LSB on the radio and press DATA for Data mode. Hold DATA to choose D1/D2/D3; this guide uses LSB-D1. |
| ACC1-A pin 4 MOD | Interface TX audio → ACC1-A pin 4 MOD. |
| ACC1-A pin 5 AF | ACC1-A pin 5 AF → interface RX input. Normally independent of the AF knob. |
| ACC1-A pin 2 GND | Connect pin 2 GND as specified by the audio interface. |
| ACC1-A pin 3 SEND | Pin 3 SEND: contact input if the interface uses PTT. Separate PTT wiring is unnecessary for this CAT PTT connection. |
| CI-V Address | Default 6Ah. 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. |
| ACC → DATA1 MOD | Set DATA1 MOD to ACC-A, selecting the connected ACC1-A audio. |
| ACC → ACC-A MOD Level | Keep working FT8 ACC-A MOD Level first. Factory default: 50%. Adjust with PC/interface TX volume. |
| ACC → ACC-A AF Output Level | Adjust RX output with ACC-A AF Output Level. Keep working FT8 settings and check PSRTTY RX level. |
| OTHERS → RS-232C Function | For CAT via RS-232C select CI-V. Decode outputs the radio’s decoded text. This setting is separate from REMOTE CI-V. |
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-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-7800)
If FT8 already works
If FT8 works with the same external audio, keep wiring/gain first. USB-D1 and LSB-D1 share DATA1 MOD, but D2/D3 have separate inputs. Match the connected audio port, Data number and input source.
PSRTTY settings · AFSK
Select IC-7800, CAT COM and explicit external Audio IN/OUT. This guide turns automatic mode switching on connection OFF: set and keep LSB-D1/input on the radio. Use CAT PTT with compatible CI-V and close apps on 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 IC-7800 documentation. Menu names/positions may vary with firmware or language.