Xiegu G90: digital and CAT control.

My uBitx v6 has been my main FT8 rig for over a year, thanks to the (discontinued) Funtronics sound card which gives me full CAT control and sound in/out with a single USB port. This is a huge advantage with Windows, since the OS tends to change audio settings erratically on my machines, both of which have a combination 3.5mm jack. Since I had such good luck with the sound card, I also ordered one of their newer universal sound cards, the HF DigiBox, which I ordered as a generic build, with no cables. Shipping to the USA takes a few days, and they are very helpful with support.

To use the HF DigiBox with the G90 you will need two 3.5mm stereo jacks and an 8-pin mini-DIN plug with cable. The DIN cable carries audio in and out and PTT (though everyone seems to recommend using VOX rather than the PTT), one of the jacks is used for keying, the other will need a longer cable as it needs to plug into the socket below the headphone socket on the head unit. For some reason CiV/CAT is not enabled on the rear of the radio.

Now, I must insert a break of almost a full year: I was never able to get the G90 working with the Funtronics HF Digibox, and I will have to come back to this in a few months. I started this post in the summer of 2023, and I have taken it up again mid May 2024 having finally got the G90 working with WSJT-X and FT8CN, using a DigiRig Mobile, with its factory cables for the G90. What is the difference between the two interfaces? Almost none, they both offer usb isolation, CAT control via a virtual COM port and audio in/out using a single USB-C cable. So why is it all working now? I had not found any mention on forums or manuals that there had been a mode change with firmware 1.79+, and that you now ABSOLUTELY MUST use D-U as your mode (Digital Upper sideband) or else the rig will not send audio to the mini-DIN.

Ok, so now that we have finally cleared this up, here are the settings you need for the radio itself:

Mode needs to be set to D-U (firmware 1.79+) for all modes that use upper sideband. This mode is necessary for the rig to send audio out the mini-DIN. Set mode by cycling the MODE button on the top, left of the BAND buttons. Alternatively, save channels for different digital mode frequencies, with the relevant mode.

Set the input to AUX LINE IN by pressing FN + POW. Pressing the main tuning knob will let you adjust the audio input level before exiting the menu. The default is 50%, and you are looking to get the ALC to 90-100%.

Set AGC:
AGC will cause issues with decoding digital signals, so turn it off by cycling through the modes until there is none visible by pressing the AGC button.

Set CMP:
Turn off the Speech Compressor by pressing CMP until the icon disappears.

Set Power:
Set the power to around 10w to avoid damaging the amplifier finals. 10w with FT8 is enough to reach most of the world with a dipole. You can always check what stations are decoding your callsign using PSKreporter. To set power press POW and rotate the main tuning knob.

Moving on to FT8, this other blog post is more thorough than I can be bothered to write, and probably overly complicated. What you need to do is follow the normal setup procedure (or clone an existing profile and modify for the G90), putting your callsign and maidenhead grid locator on the first tab. On the audio tab, select the input and output of your interface. On the radio tab, I just selected the Xiegu G90, set the CAT control to the relevant COM port (on Windows you find this via the Device Manager, if there is more than one option), and set PTT to CAT, also with the relevant COM port. If you can’t change the COM port, switch to one of the other modes, change the port, then switch back to CAT. This seems to be a bug. Then test CAT and PTT.

With FT8CN on my Android 12 phone, I found the setup to be very similar.

With either/any interface, you will need to make sure your clock is synced on your computer (use an NTP or GPS), and you are targeting an audio level on transmit which takes the ALC to 90-100%. I find this a little harder on my phone, so you may need to adjust both the output volume of the phone/computer as well as the input percentage on the G90.

Tobias Feltus: