Meta preamble

I am well aware of my long hiatus in posting, as many of you may know, I served as a Program Manager at DARPA where the results of my technical work required approvals prior to publication, and I thought it best to avoid adding commentary and other contributions in any unofficial capacity. Following DARPA, I spent a brief stint at AWS, an organization far more tight-lipped than the DoD. Now that I am at Thinkst, I have an outlet there to post interesting tidbits, but off-topic content will likely end up here for others looking for any help I may be able to provide.

Preamble

I recently renewed my interest in amateur radio, a long-time hobby started freshman year at K2CC, the Clarkson University club. Besides setting up a more robust APRS system for the car and back country trips away from cell coverage, I took the plunge and ordered a Xiegu G90, a cheap(er) SDR-based HF multi-band transceiver. As I researched radios, troubleshooting, and tutorials, I discovered an odd trend within the amateur radio community: content is shared via a limited set of means. There is a wealth of Youtube videos, websites that were designed in the 90s, or PDFs ranging from slides to hand-made user manuals. This lack of textual web content, contextualizing a few photos if needed meant that searching for even simple things was a tedious process. I am writing this (and hope to post more in the future if I find things worth sharing) to attempt to help others facing similar issues.

Xiegu G90 and Digimode-4 configuration

The documentation for the G90 and Digimode-4 is sparse and scattered. After a frustrating time trying (and not completely figuring it out) setting up digital mode applications for this radio and cable combo, I thought I'd share my findings.

Physical connections

The Digimode-4 has a USB A on one end, and two cables on the other: an 8-pin connector, and an 3.5mm audio plug. The 8-pin must be carefully inserted into the rear of the radio, the audio cable into the port on the left of the face-plate below the headphone jack (the label looks like a person in a circle). Obviously the USB goes into the USB port, the drivers for the cable are on FTDI's website. Make note of which COM port is added when you insert the USB cable, this will be used in the configuration below.

Radio configuration

1. Disable AGC by pressing the AGC button until it shows AGC-- on the top of the G90's display.
2. Set the AUX IN and AUX OUT levels to 10-15 (hold the FUNC button, then cycle through the system menu)
3. Set the input to LINE IN (press the FUNC button, then the POW button, use the knob to select input source as LINE vs MIC)
4. Disable microphone compression (CMP button on handset)
5. Ensure you're in USB mode (MODE selector on top of face-plate)

Winlink with ARDOP or VARA

Assuming you have the Winlink client software installed, as well as VARA 4, select either an HF ARDOP or HF VARA session, then hit connect to open the session connection screen. On the Winlink session screen, select configure radio, and ensure the settings look like the below figure:

Note the differing baud rates for radio control and PTT. When you hit update, the session will reload, you will still probably get an error about not finding an audio source, in the background, Winlink has loaded either the VARA or ARDOP modem, it's a smaller window with a waterfall display. You configure the audio sources here, you want to select the USB audio device for both input and output:

flrig and WSJT-X/JS8Call/fldigi

The current version of flrig has native support for the G90, flrig should be running in the background when the other applications are used, but closed prior opening Winlink. Configuration is pretty simple for flrig, it is important to uncheck the RTS and DTS boxes:

The only issue I've run into with flrig is the occasional problem where when transmitting for a digital mode, the radio will go into transmit mode (0W and no output) and hold like that, while the Windows computer throws an error about the sound device becoming disconnected. I see a few others having this trouble, so I will continue to experiment and see if I can find a clear fix. There are a couple of configuration items I want to check, as well as isolating RFI using some ferrite chokes on the Digimode-4 cables.

Once flrig is configured and connected to the radio, the other digital mode applications can be set to use flrig to control the radio, here's an example from WSJT-X (note the configuration for PTT method):

In addition to the shown radio configuration, ensure the audio tab is set to the USB audio device.

Other tips

• Ideally, when you are transmitting, you want the level such that you fill the entire bar (S level bar for receive) on the display, including the red blocks to the right. The ALC should be close to 100, which is apparently quite different from other radios where you want 2-5 bars filled to maximize power without over driving.