Summary: When I operate digital modes, sometimes I have no power output. I have no transmitter output, and the ALC meter on my radio shows nothing. When I say sometimes, what I mean is that I might work someone and everything is fine. Then five minutes later I go to work someone else and I have no power output. Sometimes I shut everything down including the PC, turn it all back on and it works again, only to stop working later.
Receive has always worked fine. Even though I couldn't transmit, I could receive and decode. Also, CAT control works. Also PTT works. I decode a signal, attempt to work them, the radio PTT works (red light goes on in the transmitter and the amp switches to transmit, and the meters on both the radio and the amp switch to show transmitter levels), but I get no transmitter output (as seen on the radio power meter, the radio ALC meter, and the wattmeter in my amplifier). Also FWIW: everything works fine in SSB voice and CW.

This problem has occurred with two different radios over a period of maybe a year (but right now, I can't transmit at all for the last several days).
The first radio is a Flex 6700 using virtual COM ports and virtual audio cables. The radio itself is connected to my home network through a hub and a network cable.
The second radio is a Kenwood TS-590s using the radios' built in sound card connected to the PC through a hub via USB.
FWIW: I have worked literally thousands of digital contacts on these radios using this same set-up, same PC, same hubs, same network............... and all of the sudden, I can't transmit. Another FWIW: I have been on digital modes for years using all kinds of radios, different PCs............. Point is that this isn't a case of a guy just getting started in digital modes having trouble making it all work. This is a guy who has been doing this for years and years not being able to make it all work.

I am currently running Windows 10.

This occurs with various software: WSJT-X, FLDigi, MARS digital software................................ Sometimes I have been using one software, it quit transmitting so I switched to a different software to see if the problem was with the software (and some setting I incorrectly made) and sometimes it starts transmitting with the different software and sometimes it doesn't.

I am out of ideas on how to troubleshoot this problem.  HELP !!!!

At this point, I am thinking the problem must be with the PC.  It's like the signal goes from the radio, to the PC on receive. But in transmit, it seems like the audio isn't going from the PC back to the radio.

Maybe RF is getting into the PC ?  But, I can reboot/restart everything, and it doesn't work and I am not putting out any RF to get into anything.

Any ideas would be nice. Is there some kind of software utility that would show the traffic on USB to see if a signal is coming from the PC back to the radio ???

I am getting desperate here. I ran out of ideas on what could be the problem and have thought about starting to throw money at the problem by buying a new PC just to eliminate that variable.  I need to run digital modes. I am a member of MARS and at the present time about 80% of the MARS nets are digital. In the near future 100% of the net is going to be digital. And as a member I am required to spend a certain amount of time on the air participating in these nets. And with this problem, I can't.

If really does sound like RF getting back to the computer. Have you tried adding a choke balun  to the feed line ?

I have tried RF chokes on every cable in my station as well as grounding everything including the computer case.

This was done several years ago because I obviously was getting RF into the computer. Dramatic evidence of RF getting into the computer. However, I haven't seen anything obvious since then led me to believe that RF was getting into the computer.

The fact that I can decode received signals, and the CAT control of the radio still works, and the PTT works, it doesn't seem like RF getting into the computer would be the problem. In addition, I can restart everything and it still doesn't work even though I am not putting out any RF.

But, I am grasping at straws at this point and am not dismissing anything. I appreciate any suggestions I can get at this point.

I had a similar problem recently with a PC i built up to use as a Winlink gateway node.  It worked fine with the USB ports controlling  the KPC3+ packet controller, and another USB port controlled one of my IC-7200 radios just fine, both the CAT and the built in sound card in the 7200.  It ran Trimode flawlessly for several days.  Then I tried to use my old Kenwood TS-450S/AT instead of the IC-7200.  I used a SignalLink USB sound card interface that I had used with the TS-450 for years in all digital modes.  I would set it up and it would work and send audio to the radio for a few minutes and then go randomly intermittent, or quit altogether until I re-booted and re-configured everything, and then it would repeat the symptoms.

I tried all the USB ports, re-installed the USB driver, and everything else I could think of. Still went intermittent after a few minutes.  The SignalLink and radio would interface fine and reliably with the USB port on two other laptops.  I finally concluded that there was some problem between the USB port and the SignalLink on that particular computer.  The computer was running Windows 7.  It has been running flawlessly for five months now as a Winlink gateway, but it will just not talk with the SignalLink reliably.  I gave up and used the SignalLink on some other project where it works fine.

All that probably doesn't help you much, but lets you know that there is at least one other unexplained incompatibility out there

I'm not reading any information on how you debugged this.

Let's concentrate on the Flex radio, because it probably has better debugging facilities.

When in transmit, when the problem is occurring, do you see Mic Level indications in SmartSDR? And when the problem is not occurring, do you see Mic Level indications in SmartSDR?

Now we come to an awkward moment...............................

Thinking the problem was with my radio, several weeks ago, I sent my Flex Radio back to the factory (and paid $175 in shipping to do it). They said that for an out of warranty repair, they won't even look at it for probably six weeks. Who knows when I might get it back, and who knows what it is going to cost me ? Again, I sent the radio back for this exact problem only to figure out at this point, it almost certainly was NOT the radio and is some kind of issue with my PC.

So I don't have the Flex Radio to trouble shoot.

I only mentioned the Flex Radio because I was having the same problem with it and wanted to add that bit of information to reinforce my theory that the problem isn't with the radio side of things: I had the problem with two different radios, which were connected to the PC by two entirely different ways: one USB and one connected to the network.

The only radio I currently have in my shack, connected to a PC is the Kenwood TS-590S.
Not that this has anything to do with this but upstairs I have a Yeasu FT-891 and a KX2 connected to a netbook, doing all this stuff perfectly.

Have you taken a really good look at your entire feedline and antenna? Maybe you have some intermittent fault causing a high-SWR situation that puts the radios into protection mode.

That or RF coming back on the feedline seem like good possibilities.

First, remove the hub. Get the 590 attached directly the PC USB port.

I'm not familiar with the 590. However, assuming you can get it to work again, when you are producing a valid transmission, does the mic level meter show a proper audio level associated with the USB sound card interface? If so, now you have a good debugging tool for seeing where the audio is and is not. As you pointed out PTT is easy, one can easily see if the radio is in TX or not. But it is less easy to determine if audio data is flowing out of the USB port. If the mic level meter is useful for that please tell us.

I have tried it with three different antennas.
Same issue with all  antennas.
In addition, I am running my feedlines through a solid state amplifier which will fault if the SWR goes above 3:1

I hadn't tried it recently with my six meter beam (the third antenna) but I just did after you mentioned this and the problem still exists on 6 meters with that antenna. Software goes into transmit, PTT triggers, no power output and no audio indicated on the ALC meter of the transmitter. So, three antennas, all exhibit the same issue.

Also, let me repeat that the radio never actually transmits: so I can't see having an RF problem when I am not producing any RF. I could see if it transmitted briefly and then the problem occurred. But if it never transmits at all, I don't see how RF could be getting into anything.

WILCO
I can also try this with a standard serial cable with RS-232. I am pretty sure the radio has that.

I have to get back with this later, unfortunately I got other issues to attend to. But this is where I am going to start off when I get back.

FWIW: I haven't messed with this radio a whole lot and when I did it was a couple years ago. I went back to it after I sent the Flex away. But, I had it working with everything as recently as a few days ago with rare intermittent episodes of this problem which were always fixed each time by rebooting the computer. I have been  using this radio for a month or so and have made probably close to 500 digital QSOs with it as well as SSB and CW. I worked close to 200 6 meter FT8 Qs with this including one on 6 meters with the Canary Islands running 1 kw and didn't notice anything happen right then to make me believe that RF was getting into anything. At that time, after running as much as 1kw, the whole setup continued to work fine. When I worked everybody on 6, I would move to 10 and work a bunch more. Nice E layer opening over a couple day period.

But, the problem was there to a small degree; it would happen on occasion. Every few days.  But now, I can't transmit data at all.

Thanks for the help and suggestions so far.

Since yours is (was) intermittent, it is probably completely different, but I had an issue a few weeks ago, with not being able to transmit on fldigi.  aa777888-2 pointed out that after a recent Windows update, that you had to go into the privacy settings (or perhaps it was the security settings....can't remember) in Windows, and enable the microphone setting, which would allow the digital software to utilize the microphone.  That solved my problem.

Apparently it was an issue that changed with the update.

Just a thought.....

I just realized what the problem likely is.

There was a Win 10 update a little while back that changed the audio setup and caused most digital mode software to malfunction.

I had this text saved on the issue:

another link:
http://www.tigertronics.com/slusbts.htm#Sound%20Card%20Error%20after%20Windows%2010%20update%20Version%201803

I was so excited by the possibility that my problem was from a Windows update that I immediately stopped what I was doing and went to the shack to apply the fix. It sounded so right. This had to be it. I felt like all the weight had been taken from my shoulders.
I am running Version 1803 of Windows 10

But, nope.

The settings there appear to be correct.
The "Microphone access for this device is on", and "Allow apps to access your microphone" is also on.
It does give a list of apps that you can give or deny permission to use the microphone and none of the ham radio software is specifically listed. And I don't see any way to specifically list them.

Shit
After racking my brain for months with this problem, this is the type of thing I envision to be wrong. It seems like somewhere there might be a setting screwed up or something and this particular setting would have caused the same problem with all digital mode software.......................

You can't do this with a standard serial cable. You need the USB interface to move the audio.

In addition to removing the USB hub, also fully review your 590 digi setup stuff. I know we've got some 590 setup experts on the arfham forum here. Who's got the definitive guide to what options to have set to what in the 590?

I'd maybe try cycling those settings off and back on, I think it's something related to that issue.

Here's another tidbit from the Signalink help page that would also apply to almost any digital interface:

Yeah, I just figured that out.
I connected it to my PC via a serial cable on COM 1 and yep, there is no audio. I might as well leave it connected for CAT control, why I don't know, but it's already connected.

I have now removed the hub (which had 11 devices connected to it) from the equation and plugged the radio directly into the back of the PC.

EDIT:
I fixed it.

I don't know what part of what I did fixed it, but it is working again.
May have been the hub, I don't know. But it's fixed.
I even went so far as to delete the configuration files on my hard drive and reconfigured all my digital software.
Whatever worked, it seems to be working OK now.

Thanks for all the suggestions.

FWIW: behind my operating position is an absolute sea of cables. Dozens of cable. I only get back there as a last resort.  My Elmer (now SK) used to say: "For a hobby that is supposed to be wireless, we sure have a lot of wires".

HA! I took a pic of my buddy (SVGA-1) behind my bench in the early 90's wrapped up in cabling.

I wanted to have a poster made that said "Wireless communications my @$$!"

No! Get rid of any cable you are not using! Unnecessary cables are breeding grounds for EMI, RFI, ground loops and, worst of all, general confusion about your setup when you go to solve a problem with it 6 months later and forgot what you did (and nobody ever makes a schematic of their radio setup).

I'm glad to read that it is working. But because you changed so many things at once, now you will never know what was really wrong with it.

And this is one of the primary sources of trouble. Having a rat's nest shithole of a radio shack is not a badge of honor! Cable management is the number one thing you can do to create a smooth running, reliable, properly operating station. Shitcan what you are not using. Organize those ground cables (you do have a "single point" ground, right?) Separate power cables, audio cables and RF cables. Do not use massively long cables that need to be coiled.

This is a photo of the back of my rack. All AC power runs in the left duct. All DC power, Ethernet and serial runs in the right duct. RF up the middle. Full height ground bar is not visible but is behind the right duct. Because it is a remote SDR configuration there are zero audio cables to worry about or manage. High power RF at the top. Power supplies at the bottom. No giant coils of excess cable (I've got one holiday on the top right, it's my GPS antenna cable, I need to fix that!)

Attached File

I didn't say I had a rats nest of cables.
I said I have a lot of cables. Actually I said I have a sea of cables, but, same thing.
I have A LOT of equipment. A LOT of equipment requires a lot of cables.
The problem is that I have about six inches of space behind my shack table. And the table is six feet long. So getting to the cable is often the issue.

They are all labeled on each end.
None are longer than they need to be.
There are no cables I am not using.
All the cables have ferrite on each end.
All the audio cables have an isolation transformer on them.
I have a single point ground buss and everything is grounded.

I see no problem here.

Well...not now that you've said all that

Except that you need to find some highly trained technician mice to run around behind there and maintain stuff for you

Not too long ago I was looking at the most amazing ham radio room on QRZ. The guy had built everything into the walls, and had built a large maintenance space behind both of the walls with equipment in it. Really phenomenal stuff. I wish I could remember the call sign...