2019-08-29 Today I made up the digital interface pictured below and had a PSK QSO with my friend Gary, KD9KHI on my G90 using HRD and DM780. Rig control including PTT was handled by HRD through the interface cable that came with the G90. That cable has to be plugged into the G90's control head and NOT into the COM jack in the back of the G90.
As the schematic shows the interface is very simple, just 2 capacitors, one in the wire between ACC DIN jack AF OUT and the tip of the plug to the computer mike or aux in and one in the wire between the ACC DIN jack AF IN and the tip of the the plug from the spk or aux out on the computer. I actually used a USB sound card dongle from an old headset rather than plugging into the computer audio in and out directly. Soldering the three wires to the tiny pins of the DIN plug was the hardest part! The layout of the AÇC jack on the G90 in the manual shows the three pins used, GND, AF OUT and AF IN.
I had a couple 0.47uf caps in my junk box but any value from about 0.2uf up would likely work. I don't like electrolytic caps in these applications because they are polarized but they would probably be OK too. Ground goes to the barrel of the audio plugs and the ring is not used. Only the tip and barrel of each are used.
Finally, you have to select the AUX IN by pressing the FUNC button then the PWR button twice and selecting LINE input by turning the tuning knob. And then adjust the transmit audio level in HRD so you don't overdrive the transmitter. I did that by setting the transmitter power to 20 watts and then slowly increasing the transmit audio up from zero in DM780 until the transmitted power out was peaking at about ten watts. Gary verified that my signal was clean and not splattering all over the place. I wouldn't push the G90 beyond ten watts and would be happier keeping it lower than that to avoid damage since digital modes are 100% duty cycle.
A few hours later I had a 20 meter PSK QSO with WA7HDZ in Washington State, 1450 miles. It was a bit touch and go but we got through it. He was running about 25 watts to a dipole, I between 5 and 10 watts with my MFJ 1984MP EFHW antenna. So it really does work!
2019-08-26 I've been having fun with my G90. I decided to use it exclusively for a few weeks so I really get to know it. So far I haven't found anything I don't like! I've got a friend who is seriously considering getting one so he stopped by today to have a look. He likes to work digital modes and had a lot of questions about that. I seldom work digital and had not even connected up the CAT control. So after he left I got the cable. I initially plugged it into the COM jack on the back. That didn't work. Glancing through the manual I noted it said to plug it into the jack on the control head. As soon as I did that all worked. HRD immediately found it with the settings for an Icom IC7000. Now to figure out the audio interface!
2019-08-17 On August 8, just a little over a week ago I got my Xiegu G90 from MFJ, four days after ordering it. After playing with it a bit I figured out how to adjust the xmit power and attach an external speaker. Then I set the power to 5w, connected up my mfj 1984MP, 40-10 efhw antenna, tuned to 14.060 and called CQ (16:46z). On first call K6HPX in AZ came back, 1435miles. He was about 449 here in WI and gave me a 519. Our QSO was brief but real! Not a bad start! My only real observation so far is that straight Key CW seems very smooth. I compared receive performance with my x5105 and IC7100 by switching the same antenna between them on the same signal. I didn't notice any important differences. I'm excited!
I'm really enjoying the G90 after about a week owning it and 41 QSOs. I've had 20 CW QSOs, mixture of straight and paddle keys with no problems at all. Also have enjoyed 21 SSB QSOs, again with no issues. All QSOs except one have been on 40 or 20 meters using my mfj 40 meter EFHW antenna. That one, was using my portable Wolf River Coils vertical at a nearby park.
Some have reported problems with buttons on the front and other things but I've had nothing but fun with mine. I'll wait a bit but if I continue to like it I'll sell my fourteen year old Icom IC-7000 100w backup radio and keep the G90. It seems like a great combination of form and function for both portable and base operation. I may even sell my x5105 which I really like after a year of use. The G90 matches or exceeds nearly everything that the x5105 does except for the x5105's "extended backpacking portability" which I dream about often but almost never do! The main difference is that the G90 weighs nearly twice as much and does not include a built in battery. Both are great little rigs and are essentially a complete ham shack in a single small package.
The automatic antenna tuner in the G90 has tuned everything I've tried with it so far and is much faster than the one in the x5105 which is nice. But both work well as far as I can tell. With the G90 I haven't worked with anything other than the mfj 1984MP, 40-10 efhw so far. But I have successfully used the x5105 on a variety of end fed resonant and non-resonant antennas.
The up to 20 watt output power of the G90 is perfect. I have for years mostly used around 25 watts for CW and about 50 for SSB even with my 100 watt rigs. And since I mostly work CW, 20 watts seems perfect. Last evening I answered a CW CQ on 40 meters from a station in Texas running 20 watts. He mentioned that he loved QRP so I dropped the power to 5 watts. He said he didn't notice any difference in my signal, giving me a 579! Propagation is everything, but that was an interesting experiment. The past year since getting my X5105 I've made 339 contacts and found that five watts can fill the log book! However, having the 20 watt option is nice, particularly for SSB!
One other thing that I really like about the G90 is its SDR architecture, most noticeable to me in the graphic display which shows both a waterfall and waveform. After a week of playing almost exclusively with that on the G90, I find all my other rigs a bit "blind" since you can only find a signal by tuning around! The G90, and I suppose all other SDR rigs, provide that wonderful graphic display of the signals. I fear that now that I have used it I will never be happy with rigs without it!