Keying transmitter causes USB devices to fail

Discussion in 'Computers, Hardware, and Operating Systems' started by WB4WOJ, Oct 1, 2020.

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  1. WB4WOJ

    WB4WOJ XML Subscriber QRZ Page

    I have a IC-7300 attached to my PC using the USB cable.
    The IC-7300 and PC are plugged into same outlet (so same ground path)
    All the USB cables have a ferrite cores on one if not both ends.
    Power output is 50 watts.
    Antenna is a wire horizontal dipole.

    When I key the transmitter for CW or digital the keyboard, mouse, and the USB cable from the 7300 will disconnect. Sometime they will cycle back, sometime I need to unplug and then plug them back in. If I disconnect the USB cable from the transmitter and run the radio without PC control, then all is good and no issues with USB devices on PC.

    Anyone have any suggestions on what I should do? I could add more ferrite cores I guess. Also, if I power down to like 20 watts then that also helps but I would like to run at 50 watts for digital.

    Any advice or experiences with this situation is appreciated.

    Alan WB4WOJ
  2. K5EMG

    K5EMG XML Subscriber QRZ Page

    Use a big ferrite core and wrap the usb cable around it like in the picture, try several different combinations of turns through the inner core hole. You can use a snap on ferrite bead, that’s what I used and it worked. Note Oct 1, 2020.jpg
  3. WR2E

    WR2E Ham Member QRZ Page

    How close is the antenna to the shack, and is it fed with coax and an appropriate balun at the dipole feedpoint?

    You can put ferrites all over the place as 'band-aids', or attack the problem at the source which could well be the antenna system.
    N0TZU and N4UP like this.
  4. WB4WOJ

    WB4WOJ XML Subscriber QRZ Page

    The antenna is about 30 feet away from the shack and along the side of the house. Going from a tree to corner of house up about 20+ feet and horizontal. It is a shortened commercial diploe (DH40SH) which has a balun at center feed. It is feed with 75 feet of RG8X into shack. I do not know what else I can do with this antenna and feed lines.

    On 40m I do not need to use the tuner and this seems to help but not always. When using tuner (like on 20m where I need it) the USB interference is worse. Only solution right now is to power down to near QRP levels. So problem probably is feedback RF, so how do I mitigate that.

    I have ordered more ferrit cores. The device that causes the most trouble is my fancy multi-media keyboard. When plugged in it causes noise on the receiver and is the first device to fail when key transmitter. So going to swap it out for a super simple cheap keyboard which should help I hope.
  5. K5EMG

    K5EMG XML Subscriber QRZ Page

    Just play with cable turns inside the ferrite core, sometimes you need several tries before be able to kill the RFI. Your antenna is to close to your home, mine is partially running over my house roof 5 feet on the air, the RFI is mostly from the antenna wire itself and not the coax. I have the same radio with an EFHW antenna.

    That’s the radio fun, experimenting!
  6. WR2E

    WR2E Ham Member QRZ Page

    Does the RG8 come right into the shack without going to a ground rod first? (it really should, but that whole discussion is a can of worms that invokes the worst in some of the QRZ trolls, so let's leave it alone for now)

    Try a big ferrite on the feedline before it comes into the shack. Loop multiple turns of the coax through the core.
  7. WB4WOJ

    WB4WOJ XML Subscriber QRZ Page

    Thank everyone for your advice and suggestions. Really much appreciated!

    I will try the big ferrite core on feed line as suggested, as well as peppering all the other USB and power cables with ferrite cores using as many loops as possible.

    I live in a duplex condo so the antenna and feed line placement is the best I can do. Being the HOA president helped get this much approved. So need to order some supplies and will post on this thread next week on results. 73.
  8. WF7A

    WF7A Subscriber QRZ Page

  9. VK4GAP

    VK4GAP Ham Member QRZ Page

    I use these all over the place (especially on the USB leads)

    20M before S6 , 20M after S1 mostly from the laptop to rig-blaster controller , then mouse , then 3g modem , then external monitor , they be kits on the bay and amaz .

    NK2U and KC3PBI like this.
  10. KC3PBI

    KC3PBI XML Subscriber QRZ Page

    ^ I used a kit like that to solve some problems around my shack, worked like a charm.
    NK2U likes this.

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