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PC interference?

I recently became interested in VHF. I put up a antenna, bought a Q5 Signals transverter and started listening. Then I noticed lots of noise on the band so I started to try and see if I could track it down. So one by one I started eliminating things and then I just happened to shut my logging program down (N3FJP) while watching the panadapter and the noise level dropped! Hmmm…. So I closed out google chrome and the noise level dropped some more. Hmmm.. So it appears if I open a program that is fairly CPU intensive? although I wouldn’t call Google Chrome intensive, the CPU pulls puts more of a strain on the power supply because it wants more power which produces more hash? At least that’s my working theory anyway. My question is how do I stop it? Right now the 2M calling frequency is pretty mush unusable as there is a spike right on 144.200. I’m running a Dell full height tower case with dual Xeons not sure on the wattage of the power supply. Thanks for any suggestions.

73 Matt



  • Jeff_W4DD
    Jeff_W4DD Member ✭✭

    Rather than radiating directly from the pc cabinet, more likely it is radiated from some cable connected to the box. Consider the video cable, usb or com cable, and power cable. You might want to make up a piece of rg58 with a small loop of center conductor at the end and use that as a sniffer antenna. Try and match what you hear on the primary antenna. Most pc power supplies are much quieter than they used to be years ago. More likely a video monitor but one never knows until you investigate.

  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    I would think ferries on all cables in and out of the PC. Maybe something like mix 43 which is more effective than mix 31 at VHF.

    If you have a portable radio try seeing if you can tune to the “birdie” frequency and if you can hear it. Then remove the antenna and put the portable close to the PAC then the monitor. Try to isolate exactly where the noise is coming from. Also check each cable coming out of the PC to see if the noise is stronger on one vs another.

    Some monitors are very noisy at VHF.

    Good luck hunting!

    Dave wo2x

  • Ted  VE3TRQ
    Ted VE3TRQ Member ✭✭✭

    I have a Dell 24" monitor as a second monitor on my MacMini. I only hear noise on VHF when the Dell is on. When it is off, and the rest of the computer is on, everything is (relatively) quiet.

  • Neil D Friedman N3DF
    Neil D Friedman N3DF Member ✭✭✭✭

    I also have a Dell 24-inch monitor (now almost 4 years old) and Q5 144 MHz transverter. I notice no difference in the (relatively quiet) noise level whether the monitor is on or off.

  • w5ll
    w5ll Member ✭✭

    Thanks guys. At least this gives me some ideas on places to start. My monitors aren’t Dell just the PC a if that makes any difference. Doubt it does. I did order some 43 mix as suggested above to put on the power cables as a start to see what that’ll do.

  • w5ll
    w5ll Member ✭✭

    Okay so I’ve isolated the issue a little further. I have two 23” LG monitors. Most of the noise seems to be coming from the secondary monitor. I can unplug it and the noise goes away. I thought we’ll I’d just order some torriods for both monitors and that would hopefully take care of things. Then I plugged it back in. My PC didn’t redetect the second monitor for some reason and the LCD screen never came back on there was power to it but no display. I had to go into Windows 10 and have it search for new display devices again and it detected it. Once it did, it displayed my extended desktop and the noise is now back. So putting torriods on the power cables power cables probably isn’t going to help much if the LCD itself or something inside is what is causing the issue?

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    If the ferrites on all cabling to the monitor don't help, another solution is to use a noise canceller like the MFJ-1026 or TimeWave ANC-4. I have the ANC-4 and it cleans up all the noisy junk in my shack. I am in the process of finding some noise from the neighbor's house, and will run a small noise antenna over that way to see if I can knock it out more completely.

    The down side of these units is that they are not remoteable. When I am home I can tune out all kinds of goofy noise, but when I am operating remotely from a camp site, I just have to live with it.

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