Connection
Connect rear USB to PC with a USB A–B data cable. Install Yaesu’s virtual COM driver; identify Enhanced COM and USB audio in Windows.
Radio settings · AFSK
Open MENU (SETUP) and select each numbered item. USB means connector audio, not USB sideband.
| Item | Setting / check |
|---|---|
| Mode | DATA-LSB：Use DATA on the LSB side for AFSK, not native RTTY/FSK. |
| 062 DATA MODE | OTHERS/OTHER: check AFSK settings rather than PSK-specific settings. |
| 070 DATA IN SELECT | REAR: select rear input, including USB; choose USB below. |
| 072 DATA PORT SELECT | USB: TX audio from the PC via USB. |
| 071 DATA PTT SELECT | DAKY: this guide uses CAT PTT, not RTS/DTR. Selecting DAKY does not require an external PTT device for CAT operation. |
| F(M-LIST) → DT GAIN | Keep working FT8 gain; adjust with PSRTTY TX volume, starting low while watching power/ALC. |
| 031 CAT RATE | Match PSRTTY baud; start with the working FT8 rate. |
| 033 CAT RTS | DISABLE/OFF: disable CAT RTS monitoring, a separate setting from RTS PTT. |
| 066 DATA LCUT FREQ / 068 DATA HCUT FREQ / WIDTH | Pass both 2085/2295Hz tones. Start with NAR off; check WIDTH and low/high cuts. |
| 064 OTHER DISP (SSB) / 065 OTHER SHIFT (SSB) | Record working FT8 settings; check dial frequency and carrier position. Changes affect both apps. |
| Audio IN / USB Audio | Select this radio’s USB Audio for Audio IN; check Windows/PSRTTY RX level. Do not confuse rear DATA-jack OUT LEVEL with USB audio settings. |
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 |
|---|---|
| Operating mode | PSRTTY RTTY / RTTY-R corresponds to radio RTTY-L / RTTY-U (RTTY-LSB / RTTY-USB), not the AFSK DATA modes. |
| PTT (TX/RX switching) | Set PSRTTY PTT to CAT |
| CAT | Enhanced COM via USB cable (CAT) |
| FSK keying output | Standard COM via USB cable (separate from CAT) |
| 060 PC KEYING | RTS |
| RTTY SHIFT PORT: FT-991 098 / FT-991A 096 | DTR |
| RTTY POLARITY-TX: FT-991 100 / FT-991A 098 | NOR |
| RTTY SHIFT FREQ: FT-991 102 / FT-991A 100 | 170 Hz |
| RTTY MARK FREQ: FT-991 103 / FT-991A 101 | 2125 Hz |
| Audio IN | Use the usual receive audio input |
Assign different signals to FSK and PTT. PC KEYING / RPTT SELECT in the table is the PTT side; the DTR/RTS selected in PSRTTY is the FSK side. For FSK on DTR, use RTS for the PTT side; for FSK on RTS, use DTR. Even with CAT PTT, do not assign the FSK signal to PTT. Do not infer Enhanced/Standard from COM numbers.
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.
Manufacturer reference: manual / USB port settings (FT-991 / FT-991A)
Manufacturer reference: manual / USB port settings (FT-991A)
If FT8 already works
Keep working FT8 COM/audio/gain. Close FT8; after PSRTTY connects, verify the radio’s DATA mode on the LSB side. Plain USB FT8 uses SSB settings; check the separate DATA input in this table.
PSRTTY settings · AFSK
Select FT-991 / FT-991A, Hamlib and CAT PTT in PSRTTY. Specify Enhanced COM, baud and this radio’s Audio IN/OUT. Close FT8 and test connection. After automatic LSB-D, verify DATA on the LSB side. Start on VFO-A without split.
No modulation
Check CAT TX and the audio path separately: actual DATA mode → input selection in this table → Audio OUT → input gain/TX volume. For missing RX, check Audio IN.
Official sources
Based on official manufacturer operating/CAT manuals. Names and positions may vary by firmware/region.