FT8 shutting down mouse/keyboard at higher frequencies

Discussion in 'General Technical Questions and Answers' started by KC9IKB, Jun 15, 2021.

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  1. KC9IKB

    KC9IKB Ham Member QRZ Page

    Pretty simple setup...Icom 7100 feeding a long wire through an Icom AT-4 antenna tuner. Running WSJT-X on a Windows 10 Pro machine.

    All works great until I go to 17 meters and above. I then experience frequent mouse and keyboard failures when I xmit. Most of the time the fix is to unplug/reconnect the offended device, but this gets very tiresome. At times xmitting on these frequencies will force the PC into standby.

    The power supply, rig, and antenna tuner are all grounded to a 9 foot ground rod about 8/5 feet into the ground. I temporarily grounded the PC to this line also, but it didn't seem to make a difference.



  2. W2SGM

    W2SGM XML Subscriber QRZ Page

    Your soil conductivity may not be what it needs to be, and you have RF in the shack. Are you able to test running a long wire along the ground underneath the antenna and attaching it to the ground stake?

    Just a note, if your ground rod is not bonded to your AC service ground, you have a ground current path running through your radio. This won’t affect your RF problem, though.
  3. N8YX

    N8YX Ham Member QRZ Page

    I got into the same situation with my FT-980/FC-757AT combo feeding a 6BTV roughly 60ft from where the rig and PC are located.

    Snap-on chokes (all LAN cables, monitor cables, PC power cables, coax feeds, etc.) cured the issue. My installation is grounded well but PC peripheral connections just love to pick up RF.
    WB5THT likes this.
  4. G8FXC

    G8FXC XML Subscriber QRZ Page

    This is a common problem and there is no single answer, I'm afraid. You are getting RF feedback into the rig and the problem is not going away until you block it.

    Good grounding is certainly important, but it is seldom a sufficient solution. Using an unbalanced long wire is certainly making things a lot worse - is switching to a balanced antenna such as a dipole out of the question? If so, then your only solution is going to be a lot of ironwork on all the cables. Get half a dozen or more ferrite toroids of the right size and grade and start threading cables through them. This is the kind of thing you want : https://www.rsgbshop.org/acatalog/Ferrite-Ring-654.html#SID=41 - make sure you get the type 43 or similar and buy them large enough to take a good ten or twelve turns of feeder. Put one on the feeder close to the AT-4 - loop the feeder through repeatedly to get ten or more turns on there. Also make sure that the AT-4 is grounded to a decent ground rod or a ground plane of wires - your long wire is unbalanced and you need somewhere to dump the opposing RF current - at the moment it's going back up your feeder and into the shack.

    Put more ferrite toroids on all the cables in the shack - particularly the cables into the computer. Again, you need multiple turns through the toroid and close to the plug. Put them on the mouse and keyboard cables close to the plug. Another one on the feeder after it comes into the shack will certainly help. Experiment with USB cables, mice and keyboards - and don't assume that the most expensive will be the best... I have had serious RFI problems over many years and it is quite often the case that a cheaper cable is more immune that a top-of-the-range one.

    Don't be tempted to go for clip-on ferrites - you need significant numbers of turns to get the necessary inductance and no clip-on will do it at HF frequencies.

    Martin (G8FXC)
    KX8C, WB5THT and KD9VV like this.
  5. N8YX

    N8YX Ham Member QRZ Page

    Clip-ons did work quite well for me. About 40 in total. There are multiple PCs running at my operating position (some work equipment; others personally owned) and every cable had a ferrite clipped on to it. LAN cables and WAN feeds got several as did the coax cable from the tuner to the antenna (before the cable exit point). All power feeds to the computers and support devices got at least one per supply cord.

    No further problems even with the rig running maximum power.
  6. KC9IKB

    KC9IKB Ham Member QRZ Page

    Thanks for the replies.

    I did go and run a long wire under the antenna wire and connected it to the ground rod, no real difference.

    Given our small property, HOA restrictions, restrictions in what the better half will put up with, it seems a dipole is out of the question. So, barring other suggestions it looks like I'll be making an investment in the ferrite industry. I'm going to try clip on first as I can get them in just a day or so. If they don't help I'll step up to the big ones.

    Any other thoughts...sing out!


  7. W9KEY

    W9KEY XML Subscriber QRZ Page

    Most likely eliminating RF in the shack via a good Common Mode Choke (CMC) will cure most of your problems.
    Anyone running digital modes, which rely on USB ports, should make and use CMC's. Simple and inexpensive to construct.

    Everything you need to know is here:

    Actual models can be constructed from data in the spreadsheets at the bottom of Page 8 (Table 5).
    WB5THT likes this.
  8. KE0QQQ

    KE0QQQ XML Subscriber QRZ Page

    Would you be willing to describe the actual hook up or take a snapshot of the shack ? Do you use some sort of cable or a box of some sort to connect to the PC like a sound card thing? Is there 2 cables involved or just one?
    I have done my share of boo-boo's trying to make my set up go. I try to make the coax lead away from all the other wires. This can be challenging.
    Try to remove all other grounds and run on just the 3 prong of the power supply as a step. Set the power lower. Ditch the tuner. Tuners are yucky. Can you test the SWR without it? What are the details of this long wire? Is there some sort of box attached to the long wire or is the wire simply attached to the center of the of the coax. How long is this wire?.
    Do you have some sort of thing like a MFJ-915 before attaching the coax to the radio? I do that and have 18ft of coax wrapped up in a 6" circle to break the wiggly lectricity before it hits the radio. The coax is acting like a counter-pose with my assumption and you need to shake that off.
    I can always tell when my problems are there when I attempt to touch the touch pad when transmitting and the touch pad stops working until I reboot. Lesson there is dont touch the touch pad while transmitting.

    P. S. 6 meters is OPEN !!!
    P.S.S. I read your page and have more details. More wire if you can or describe more of you antenna. Is there a Un-Un involved? I use no other grounds other than the 3 prong outlet for my situation with my 9:1 match box
    Last edited: Jun 16, 2021

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