QRP & Portable Rigs

Setup notes for the small rigs the community runs POTACAT with in the field — Xiegu, QRP Labs, (tru)SDX, and sBitx.

Xiegu G90

• Baud rate is the classic G90 failure. The G90’s factory CAT baud is 19200; if POTACAT is left at the default 9600, the radio just silently ignores everything. Set 19200 in the rig settings.
• Connect as Other Rig (Hamlib) at 19200. If the G90 profile won’t read the frequency, some users have success selecting the X5105 (or IC-718) model instead.
• ATU: the G90’s CAT protocol has no working remote-tune command — use the front-panel tuner button. This is a radio limitation, not a POTACAT one.
• The TX power slider is a percentage of maximum power, not watts — 50 on a 20 W radio means 10 W. (True for every rig, but most noticeable on QRP radios.)
• ECHOCAT audio: the G90 only passes USB audio in U-D (data) mode, but in data mode ECHOCAT hides the SSB PTT button (PTT is shown for SSB/FreeDV only) and you can’t switch modes back from the phone. Plan your mode before you walk away from the radio. Audio interfaces in community use: Xiegu CE-19, DE-19, and xggcomms units.

Xiegu X6100 / X6200

• X6100 on a Raspberry Pi: the proven path is bridging through FLRig. Run rigctld -m 4 -r 127.0.0.1:12345 (Hamlib model 4 = FLRig), then set the POTACAT rig type to rigctld Network at 127.0.0.1:4532. Pointing Hamlib directly at the X6100’s serial port at 19200 has been slow or failed to QSY for some users.
• X6200: if ECHOCAT’s FT8 view decodes but desktop JTCAT shows no band activity, turn up the RX level slider in JTCAT — the input level defaults too low for this radio.

QRP Labs QMX / QMX+

• Connect as Serial CAT (Kenwood) on the QMX’s first USB serial port at 38400 baud — don’t use Hamlib. If the QMX gets stuck in terminal mode, power-cycle it.
• Set the Radio Model dropdown to QMX — it’s separate from the connection settings, and the QMX-specific behavior only applies when the model is selected.

Remote CW keying

Remote CW on the QMX requires firmware 1.03 (1_003_0) or later for DTR keying on the second USB port. The confirmed working recipe:

Warning: On Linux, the kernel’s cdc-acm driver can’t toggle DTR on the QMX’s USB ports, so real-time paddle keying fails with Operation not supported. Use an external FTDI/CH340 USB-serial adapter into the key jack as the CW Key Port, or stick to CW text macros, which go over the normal CAT connection and work fine.

Other QMX notes:

• Linux: if saving the rig fails with “Cannot lock port”, you can hand-edit ~/.config/potacat/settings.json — give the rig type: serial-cat, port: /dev/ttyACM0, baudRate: 38400, disableDtrRts: true.
• Very faint phone audio through ECHOCAT is usually the radio-side output level — turn it up on the QMX.

(tru)SDX

• Works out of the box as Serial CAT (Kenwood) at 115200 baud.
• Power expectations: roughly 0.5 W on USB power alone, about 5 W on a 12 V supply.

sBitx and other ALSA-only Linux radios

POTACAT is a Chromium-based app, so its audio dropdowns show only devices that PulseAudio/PipeWire publishes — raw ALSA hw:/plughw: devices are invisible by design. The sBitx image disables PulseAudio entirely, which hides the radio’s loopback devices from POTACAT.

The fix is to re-enable the sound server and publish the loopbacks as named devices:

1. Re-enable PulseAudio (comment out autospawn = no in /etc/pulse/client.conf) or install PipeWire: sudo apt install pipewire pipewire-pulse wireplumber
2. Publish the RX loopback: pactl load-module module-alsa-source device=hw:1,1 source_name=sbitx_rx
3. Publish the TX loopback: pactl load-module module-alsa-sink device=hw:2,0 sink_name=sbitx_tx
4. Persist the load-module lines in /etc/pulse/default.pa so they survive a reboot.

The named sbitx_rx/sbitx_tx devices then appear in POTACAT’s audio dropdowns. The same pattern works for any Linux SDR that only exposes ALSA devices.