So I did a bit continuity test. When the Audio cable is disconnected from the digirig dongle but connected to the rig, the supposed ground PIN on the audio cable is shorted with the radio’s chassis, all other PIN are not grounded, which is what you would expect.
However after connect the cable to the digirig dongle, both AFIN and GND became shorted, which is kinda…weird?
You can check audio lines inside Digirig with nothing connected. Neither should ring to the ground.
Okay I will do it now.
I did your test and some more, what I found out is:
The RINGS are not shorted to the USB ground when offlined.
The AFIN and GND would only become shorted when digirig are connected to both the PC and the rig. It isn’t shorted to ground when it is only connect to either of them.
Is this the case when radio is disconnected from power and antenna?
There may be some weird ground loop going on and your continuity tester may be triggered by external voltages. You can also isolate Digirig from computer with USB isolator:
Thanks for the suggestion.
You were right, well, sort of. The ground short was indeed caused by some weird ground loop, after disconnecting everything except the ACC2 cable, the short is gone.
However it doesn’t seems to have any effect on the volume issue I had. After the loop is gone I rewire the cable back to its “normal” wiring, putting up a dummy load, and did a test transmission. The result, as always, is really low.
So I’m pretty much clueless now.
Still, I’m gonna get some USB isolator. The one that digirig sell isn’t going to do the job because the SDR needs HSUSB. I found some that support HSUSB from China, hopefully they can provides some isolation
Got a email from digirig forum that reminds me I haven’t post any update about this issue… So if nothing else, this will be my final update on this:
Still low on volume after putting on USB isolator. I guess I will just have to keep using it the “wrong” way then, after all, it seems to be doing just fine that way.
On the side note, the USB isolator indeed did a number of interesting things on my setup: in combination with the IF buffer it elevated a few minor issues I had. And by the way, the isolator that support USB2.0HS turns out is emitting too much RFI to be any useful.
Sorry to hear that you are still having problems but FYI I am having a great time with my Digirig mobile and TS-570D (unmodified) on FT8/FT4 in fact I took part in a local FT4 contest last month and did not do too bad. The only difference between the TS-570D and and TS-570D(G) is firmware related and mainly focuses on CW improvements. I think if you could try the same setup that I am using: RX, TX and PTT via the 13 pin din ACC2 connector you would have no problems, like me, remember if you use the PTT on the ACC2 input you have to use the TX audio input on the ACC2 plug as well because it mutes the other TX audio inputs. Good luck.