Connection
Use a data-capable micro-USB cable. USB carries CI-V control and transmit/receive audio; no separate audio interface is needed for this connection. Follow the official USB driver instructions.
Radio settings · AFSK
Check MENU → SET → Connectors. USB here means audio through the USB port, not the USB sideband mode.
| Item | Setting / check |
|---|---|
| Mode | Use LSB-D as the starting point: SSB Data, rather than the native RTTY mode. |
| DATA MOD / DATA ON | USB: modulation source for both LSB-D and USB-D. |
| USB MOD Level | Keep the working FT8 value first. Factory value: 50%. Adjust together with PSRTTY transmit audio. |
| USB AF/IF Output → Output Select | AF: received audio to the PC. |
| USB AF/IF Output → AF SQL | OFF (Open): prevents radio squelch from muting audio to the PC. |
| USB AF/IF Output → AF Output Level | Keep the working FT8 value and check receive level. |
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.
Connect the radio to the PC with one USB cable to use FSK. See FSK keying output for the radio settings.
Radio settings
| Radio item / connection | Setting / matching |
|---|---|
| USB Keying (RTTY) | USB (A) DTR / USB (B) DTR |
| USB Keying (CW) | OFF |
| USB SEND | OFF |
| Operating mode | RTTY / RTTY-R |
| RTTY shift | 170 Hz |
| RTTY Mark frequency | 2125 Hz |
For radios with A/B ports
| Shared CI-V port | USB Keying (RTTY) |
|---|---|
| A | USB (A) DTR |
| B | USB (B) DTR |
A/B identifies a port; DTR/RTS identifies its line. When sharing CI-V, select the same A/B side for USB Keying (RTTY). CI-V on B depends on the model/port-function setting. The original IC-7300 has no A/B choice: select DTR/RTS only.
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 uses USB-D, DATA MOD and USB MOD Level are shared with LSB-D. Verify LSB-D after PSRTTY connects and start with the same source and gain. If FT8 uses plain USB, it uses DATA OFF MOD; PSRTTY in LSB-D uses DATA MOD. Check the Data-on input separately.
PSRTTY settings · AFSK
Select IC-705 and CAT PTT via CI-V. Choose the CI-V COM port and explicitly select the same IC-705 USB audio device for Audio IN/OUT. Start with LSB-D. Close other software using the same COM port before connecting.
No modulation
Compare FT8 and PSRTTY output devices → verify LSB-D after connection → check DATA MOD = USB → check USB MOD Level and PC/PSRTTY transmit volume. Start with low audio and observe radio power and ALC.
Official sources
This setup is based on official specifications and manuals. Menu names and positions may vary with firmware or display language; follow the manual and display for your unit.