The battle against RFI in the shack

I had not mentioned this before but ever since I set  up my HF station last year I have had off and on problems with RFI in various devices. This was not much of a problem when 10m was open as I spent much of my time there and my problems were showing up mainly on 20m. First there was the issue of my Eaton ACFI breakers tripping when transmitting on anything below 17m. This is a well documented problem but I lived with it until just last week when I replaced them with standard breakers and installed GCFI outlets. That settled the issue of visiting the breaker box after playing radio.

It seemed as though whenever I made even minor changes to the station wiring I would get RFI into either USB peripherals or get RF breaking the squelch on my 2m rig which I leave on when using HF. The worst problems of this type were on 20m. SSB would be relatively minor at 100W but PSK31 on 30W would drive some stuff crazy. Her’s a list of stuff that would go wacky at various times:

  1. USB Conference speaker would light up like a Christmas tree and hang
  2. RTL-SDR dongle would over load when I transmit and freeze
  3. USB keyboard would lose connection
  4. SignaLink would drop occasionally during transmit
  5. Squelch would break on my 2m rig when using PSK31.
  6. LCD computer monitor would pick up RFI during transmit
  7. Cable modem would drop internet signal.

These were the main issues and I should note that these did not always happen. The last straw came when the keyboard would lock during PSK31. Makes it hard to close a QSO when you can’t type….arrrgh!

So the battle was joined. First up I adjusted all the wiring on the radio and tuner and attempted to keep things from being to close to cables carrying RF. I added a line isolator right out of the rig. Some improvement preventing the 2m rig RFI but not much else. Off to Amazon and Ebay next to buy some snap-on ferrites. Didn’t have much luck with these initially. Today I got into it a lot deeper and found success. A snap-on ferrite on the power supply wire to the cable modem and making sure the feed-line was not in proximity to the cable line outside fixed the Internet issue. Next the USB cables. Ideally, six turns around the snap-on ferrite applied to the USB cable where it connects to the computer settled down the USB speaker. The same was done with the SignaLink, RTL-SDR dongle and mouse, keyboard USB lines.  Also coiled up the excess wire into an air-choke. The results have been very nice. Everything is behaving now. The RTL-SDR dongle was moved a few inches away from the radio and with the snap-on ferrite it no longer overloads when I transmit.

Photo Sep 06, 6 34 12 PM


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