Connection
Connect PC to SCU-17 by USB and its DATA jack to the radio rear 6-pin jack with the matching cable. Connect SCU-17 RS-232C to radio CAT with a straight cable. For Digirig, use the RS-232 version and model-specific audio/CAT cables.
Radio settings · AFSK
PSRTTY uses audio AFSK. Use PKT-LSB on FT-950 or DATA USER-L on FT-450, not FSK RTTY.
| Item | Setting / check |
|---|---|
| CATRATE | Match CAT speed (4800–38400). |
| CAT RTS | OFF; PSRTTY uses no hardware flow control. |
| D TYPE | USER-L / DATA |
| DIG VOX | OFF |
| FT8 / PSRTTY | FT8: USER-U → PSRTTY: USER-L |
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.
Use a compatible external FSK interface to pin 4 (FSK IN) and pin 2 (GND) of the rear 6-pin connector. Select a COM separate from CAT. Never connect RS-232 levels directly to the radio.
Radio settings
| Radio item / connection | Setting / matching |
|---|---|
| Operating mode | Set D TYPE=RTTY. The radio uses DATA + LSB (DATA + USB for reverse); select RTTY / RTTY-R in PSRTTY. |
| PTT (TX/RX switching) | Set PSRTTY PTT to CAT |
| FSK input / keying | DATA |
| FSK keying output | 4 FSK IN / 2 GND |
| PTT | 3 DATA PTT / 2 GND |
| Serial connection | Use a separate FSK COM port from CAT for this model. Check the connection and avoid PTT signal conflicts. |
| D TYPE | RTTY |
| RTY SFT | 170 Hz |
| RTY TON | 2125 Hz |
| RTYTPOL | NOR |
| Audio IN | Use the usual receive audio input |
Use SCU-17 Standard COM or a compatible FSK interface COM. SCU-17 defaults to FSK=DTR, PTT=RTS; internal switch S1001 can swap them. Match the actual switch setting. An ordinary Digirig audio cable does not replace an FSK output. Connect receive audio to Audio IN. 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 |
The table shows PSRTTY control-signal logic. Match radio POLARITY TX / TX polarity and interface inversion, then verify Mark/Space with the RY test. RX decoding inversion is a separate setting.
If FT8 already works
If FT8 works, keep the same audio devices and cables.
PSRTTY settings · AFSK
Select model, CAT COM and speed. Connection mode: LSB-D. Choose CAT PTT or External connection. For external PTT, select a separate COM, RTS/DTR and Radio PTT control, then test. Explicitly select SCU-17 USB Audio CODEC for Audio IN/OUT.
No modulation
No audio: check Windows app/input volume and mute, SCU-17 TX/RX knobs, audio cable and radio DATA mode.
Official sources
Checked against manufacturer manuals and Hamlib 4.7.2. Follow the actual model/firmware manual for display differences.