Friday, August 20, 2021

Digital modes with a Xiegu-G1M and DigiRig

Prompted by carrying too much equipment on a SOTA outing, I purchased a new low cost QRP transceiver from China. The Xiegu-G1M is very small and was dwarfed by the SignaLink USB I normally use for digital interfaces so I sent off for the new Digirig interface and have been working to get it going.

As there's no VOX I need to control PTT via CAT. The G1M manual is rather vague about CAT control and the radio doesn't appear in the Hamlib options yet. The user guide suggests using IC-7000 but that didn't work for me. IC-7300 worked to some extent but was very slow, including PTT on and off.

Examining the event log in Fldigi, I could seen loads of errors and timeouts which would explain the slow operation.

I took the RigCat IC-7300.xml and stripped out everything except frequency and PTT. Later I found the xml for the Xiegu-G90 and took the mode setting from that. Rig control works enough now for digital modes. I've put Xiegu-G1M.xml up on GitHub. (Download the raw file and configure Flgidi rigcat to use it). 

The serial connection on the DigiRig is 3V and this talks nicely to the G1M with a straight through 3.5mm stereo cable. Next step is to make up a cable for audio in and out.

One note on the Digirig... one of the 3.5mm sockets broke off after light usage. It looks like the connectors are surface mounted and there's not much solder there so I re-soldered them and hope they'll hold up to normal use now.

The Digirig interface is a very neat device containing a USB hub and both serial and audio interfaces working through a single USB-C cable. I feel the 3.5mm sockets are a weak point though.

I've made up an audio cable with a 100uF cap to block the DC bias on the mic. All seems to work fine with fldigi.

Listening off air, the transmit audio sounds a bit over-driven - I may need to add some gain reduction on both transmit and receive. A bit more feedback to the fine Digirig makers - the 3.5mm sockets are very close together and I hunt around to find plugs that were narrow enough to fit.


Dave_C_ said...

Thanks for this, I’m having trouble with my G1M, I’ll see if I can get it going with this.

Unknown said...

Thank you for the write up.
Re. the SMD socket situation: This is a rare occurrence, but just in case I'm switching to through-hole mount part in upcoming production
Re. DC bias capacitor: Digirig has 10uF on each of audio lines internally so there is no need for additional one.

73 de K0TX