Low HF Bands wiped out by mainsbourne Interference

Discussion in 'Interference Problems' started by Colin B Wilkinson, Feb 9, 2020.

  1. Colin B Wilkinson

    Colin B Wilkinson New Member

    Hi to all,
    I have just signed up to your forum because after 31 years as a radio amateur i am completely stumped with the intensity of this mainsbourne interference.
    It starts on the long wave band all the way through to the 40m band. the interference is white noise, my noise floor is between -30 dBm and -40 dBm, 24/7 it never stops unless there is a complete mains outage like there was this morning because of the bad storms, it was absolute heaven (silence is golden).
    This has been going on since before Christmas approx 3 months, i have tried all the usual things like switching my mains off, it was still the same. ive checked with my neighbours on both sides and all seems ok.
    I have sampled the mains with my homebrew spectrum analyser and it is definitely on the mains and is very strong.
    The interference does spike at 160m 80m and 40m so i suppose it could be Ethernet over mains on steroids!!
    I look forward to any suggestions as to what i can do about this problem.

    Colin G0NQE
  2. Ken G3SDW

    Ken G3SDW Moderator

    Hi Colin, thanks for posting on the Forum.

    You say its mains born, if that is the case then i assume that with all antennas disconnected it is still there.

    Good on turning off your mains, what about both your neighbors, you only say all seems OK, they will need to turn off there mains supply too, and off i meant at the main fuse box.

    Ethernet over mains, doubt it as amateur bands are notched.

    If it is as you say on the mains supply then what sort of mains filtering are you using?
    Last edited: Feb 9, 2020
  3. Colin B Wilkinson

    Colin B Wilkinson New Member

    Hi Ken,
    Both neighbors have switched there mains supply off but the noise was still there i have a mains filter from the supply in the shack, and yes with the antennas disconnected the noise is still there, if i unplug the patch lead from the back of the rig the noise is gone, with just the patch lead connected the noise is back. I have run the rig from batteries and the noise is exactly the same.
    The mains runs from house to house along the back of the houses, i have used a portable radio near the mains cable down lead and it knocks out strong broadcast stations, the mains went off this morning and all went quiet.
    I have tried several clip on ferrites on both the tails from the electric meter to the fusebox and it was still the same.
    I have erected my fishing pole vertical about 80ft from the house and connected my rig to a battery but the noise is exactly the same.
    I have some photos of the spectrum analysis i did, i will resize the file and send it.

    73, Colin G0NQE
  4. Ken G3SDW

    Ken G3SDW Moderator

    That will not be needed Colin, seems as though you have done some extensive tests.

    The patch lead experiment worries me a bit, as if it is coming up from the mains then it would,not matter whether the patch lead is connected or not, have you replaced the patch lead yet, simple i now but often it is the simple things that fox us all.

    Every one i talk to says the same thing and falls into the same trap, going close to a mains supply cable with a portable RX will notice extremely high noise levels, but that does not mean that is the problems.

    But and a big but if the mains supply is off like today's outage then the noise has gone means that it must be coming from another neighbor close by, with those signal strengths it must be very close to you.

    Your next step is to try with a decent RX to locate the exact property it is coming from using a DF loop if you have one at hand, hopefully other neighbors will be as cooperative as your direct ones have been.

    Let me know how you get on if you could
  5. Ken G3SDW

    Ken G3SDW Moderator

    One other thing Colin, if you want to go down the route of mains filltering etc then i must say that not any old ferrite will do, you need to look at Ian`s GM3SEK page were he tells you what type of ferrite you should use.
    http://www.ifwtech.co.uk/g3sek/in-prac/index.htm#big31
  6. Colin B Wilkinson

    Colin B Wilkinson New Member

    i have sampled the mains with the spectrum analyser using a ferrite transformer around the cable, the trace was exactly the same as when i plug any antenna into the analyser.
    My portable receiver with hf bands is just swamped anywhere in my house, my back garden, same with my immediate neighbors.
    I did try different patch leads but all gave the same noise level when plugged in, whatever it is its very strong without a doubt.
    All understood about the mains filter ferrite.
    I believe that with the tests ive done that our mains is just radiating this high noise level like a big antenna and my antennas are picking it up, i have made multiturn receiving loop and ferrite loops and the results are the same, the multiturn loop is for 160m and 80m does null out the noise a little but not enough to make any difference.
    i dont know any other people in the street so i'm not going to go knocking on doors just to get told to go away or words to that effect.
    I'll just keep plodding on and use the Hack Green web SDR receiver its not ideal but better than nothing, with any luck the noise will disappear in the near future but i'll not hold my breath.
    I'm afraid that all this noise is going to get worse for everyone, money talks and always will, were a minority that don't pay licence fees so were worthless in the eyes of the powers that be (rant over).
    I did send photos of my spectrum analysis to the emc email address in Radcom about 2 weeks ago but didn't get a reply.
    Thank's for your help Ken, i will let you know how i get on.

    73, Colin G0NQE
  7. Ken G3SDW

    Ken G3SDW Moderator

    Please do Colin, just remember there is not a magic fix to eliminating RFI and the owner who ever they are, cooperative or not, will play a big part is getting it sorted, keep them sweet at all times.

    Keep in touch.

Share This Page