Virtual Com Port Failures on Yaesu FTDX-101

Update Feb 2024

Everything in the original post is still true and valid, but Chris Day, ZL1CVD may have determined the root cause of the hardware failures in the radio. Best to watch his videos on the subject as documenting it here would take some effort. The short story that Chris theorizes is removing one unnecessary capacitor might eliminate this failure from happening.

Part 1
Part 2

Original Post About This Issue

I never got too worried about pursuing having “proper” ham shack grounding, for a few reasons:

  • Everything works fine and I’m Making Contacts
  • There seems like 6 million different opinions on what is the right way
  • I don’t like articles/videos that say you must do this, or the world might end, but never show any empirical evidence that proves the point. Please, show me a shack with a stray RF problem, put in proper grounding, and prove the problem went away. I never see this.
  • I did have grounding, just probably not “proper”

I have the ARRL book about Grounding and Bonding. Of course, shortly after I got it, they came out with a revised version. It didn’t really change my mind.

So my opinion may have changed due to other events. I bought a Yaesu FTDX-101D in May 2019. I’m not sure when exactly, but I had a problem with it early on. I was not a major problem, but it caused an advertised feature to not work properly. The FTDX-101 has a built-in soundcard, and a Silicon Labs chip that provides “Virtual Comm Ports” that will appear when a PC is connected to the radio via a USB cable, and the proper driver is installed on the PC.

I may have seen them initially, but not sure. At some point I was trying to run WSJT-X and these ports were not showing up in my PCs device manager. I kept uninstalling and reinstalling drivers, changing USB cables, but nothing worked. Interestingly, WSJT-X was still decoding signals via the USB cable. But Ham Radio Deluxe (my rig control and logging program) needed those virtual comm ports. My PC has an old-fashioned serial port, and the FTDX-101 accepts a regular serial cable, so I was able to get it all working without those comm ports.

I kept thinking I had a PC problem or driver issue, and the radio was pretty new, so I lived with it. As the end of the warranty period neared, I looked into it again, and finally realized it must be an internal problem on the radio. I called Yaesu and discussed with their tech support, and they said, yes, it needed a repair. Under warranty, it did not cost me anything, they paid shipping both ways (it did cause me some angst though, see this post).

So it was working for 8 months or so, and it happened again. Now I’m out of warranty. The repair was guaranteed for 90 days. So I thought about just using my workaround again, but things were different. WSJT-X was not decoding signals this time. Also, the radio was acting strange, randomly keying up, display getting froze up, etc. If I disconnected the USB cable from the radio, it was working OK. So my workaround would not work without some additional interfacing of the audio signals.

Another call to Yaesu, and yes, it needed a repair. They mentioned something about “fuse” in the USB circuit. So I thought about it, and dug out the schematics. Crazy number of pages, very fine print. But I found the area in question. Not sure about “fuse”, but saw some surface mount ferrite beads, and 1 ohm resistors. I suppose they might be what he was talking about. Tiny, tiny components. I am not skilled enough or equipped enough to attempt this. I did see this whole circuit was on the “AF Board”. With the covers off the radio I checked out the AF board, and it looked not too bad to replace. Then I looked in the service manual for any adjustments or alignments on this board. I did not see any. So I called Yaesu and asked for the Parts Department. I asked what was the price of the board? $288. Actually better than I thought. I knew shipping would probably be around $200 to send the radio back and then back to me, plus Yaesu labor and any other parts, so this looked like a lower cost solution. But I thought, better call tech support and see if there is something I don’t know.

So I called, and they told me that the boards are not “plug and play”. There are alignments and setups that need to be done. Though I did not see any in the service manual about this particular board, I wasn’t going to argue with him. He either knows something I don’t, or that is just the standard answer.

So I had to make a decision. It is an expensive radio (for me), only 4 years old, it really needed to be fixed, and why take a chance just to avoid shipping cost (and possible damage and wear and tear). So I packed it up again and shipped it back to California

So I started researching this problem, and asked Yaesu tech support. They recommended using a good shielded USB cable. Online, I see people recommended using a USB opto-isolator. Fairly cheap possible solutions to avoid this again. It still bothered me that just hooking up a USB cable could damage internal components. After all, USB is supposed to be hot-swappable, though I don’t think I ever connected it with power on.

The more I thought about it, it finally dawned on me. I have a End Fed Half Wave antenna. I don’t use it that often, but I have needed it on some bands, like 80M and 30M. There have been times (not always) when using that antenna, where one of my PCs across the room will play the USB connect/disconnect chime over and over when I was transmitting. And the PC connected to the radio would occasionally have issues, with software acting up, and I might also see the radio reacting, like relays clicking at inappropriate times. So it appeared that using this antenna, I was getting RF in the shack, particularly the computers, one of which was connected to the FTDX-101D. My use of that antenna was not a lot, and I don’t think I used this antenna recently before the problem reoccurred, but it may have done some ESD damage to components, which subsequently failed. I can’t be sure this was the problem, but could very well be.

So it caused me to look at additional things, like adding a common mode choke for the EFHW. Also improving my station grounding. I am on the second floor, and according to this well written paper, it really isn’t a good ground at all. I found this article on the Flex Radio website (actually written by DU1ANV), and I found it informative. More empirical evidence would be nice, but I likely will be trying to ground my shack using the Alternative #2 method of a RF Suppressor Ground System using RG8 coax for the ground wire down to the ground rod.

The FTDX-101D should be back here Thursday this week. I got the bill and paid them, and sure enough, they replaced the whole AF Board. I got that part right, who knows if they did any special alignments or adjustments. I will use the new USB cable and opto-isolator, add the common mode choke for the EFHW, and probably avoid that antenna for a while. I only need it for 80 meters, and don’t get on there that much.

These solid state radios with so many features and complexity, with many ESD sensitive parts. I have regularly been disconnecting my antennas at any sign of a thunderstorm, but maybe RF in the shack was enough to cause a part of parts to fail. Maybe it is a design flaw on Yaesu’s part, I don’t know. I just hope it doesn’t happen again with the precautions I hope to have in place.

Grounding good.


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