Part of our The Icom IC-7300 Mark II: The Complete Guide.
Since the Mark II handles digital mode audio over its own USB-C connection rather than a separate interface, most problems trace back to a small set of causes. Here’s the order I check things in.
No decodes at all
Confirm the radio is on the right frequency and mode, and confirm WSJT-X has the correct USB audio device selected, since the Mark II presents its own dedicated sound device over USB-C rather than relying on a separate sound card. Watch the waterfall for any signal at all before worrying about decode quality, a flat waterfall points to an audio routing problem, not a software bug.
Weak or garbled decodes
If you’re seeing some decodes but fewer than expected, check that receive audio level isn’t too hot, an overdriven signal into WSJT-X hurts decode quality just as much as too quiet a signal. The audio level indicator in WSJT-X should sit comfortably below clipping.
You’re not being heard, but you’re decoding fine
This is almost always a transmit audio level problem. Check the data input gain in the radio’s menu, and watch the ALC meter while transmitting a test tone, light activity without pinning is the target. Pinned ALC means you’re overdriving and generating splatter.
PTT not keying the radio
Confirm WSJT-X is set to use the correct virtual COM port for PTT, since the Mark II’s dual USB-C ports mean it’s easy to point software at the wrong one. If PTT stops working after it was previously fine, check whether another program grabbed the same port, which is more common than you’d expect when running multiple radio programs at once.
My troubleshooting order
- Confirm frequency, mode, and that CAT control is reporting correctly.
- Check the waterfall for any signal before worrying about decode quality.
- Verify receive audio level isn’t clipping or too low.
- Check transmit ALC while sending a test signal before assuming a software bug.
- Confirm no other program is holding the correct virtual COM port for PTT.
Nine times out of ten it’s a level or a port mix-up, not a genuine hardware fault. Work through this list before suspecting the radio itself.
Setting this up from scratch? Start with Getting on FT8 with the Icom IC-7300 Mark II, and see Understanding the Mark II’s Dual USB-C Virtual COM Ports if PTT is pointed at the wrong port.