Wide band Interferance covering 4M, 6M and more

Discussion in 'EMC Matters' started by Paul Selwood, Apr 16, 2018.

  1. Paul Selwood

    Paul Selwood New Member

    For several moths I have been experiencing interferance that covers the whole of the the band 37 to 72 MHz. I am receiving this on My FT847 with a 6M/4M antenna. On SSB this shows up as intermittant noise spikes but when AM is selected it is a solid signal peaking at 20dB over S9. Using the wide graph on WSJT the spectrum obtained is attached.
    I have satidifed myself that this interferance is not being generated in my property by using an FT817 on battery power and turninfg off the incoming mains supply to the property. The only thing this does leave running is the Smart Meters.
    Anyone any ideas?

    Attached Files:

  2. Ken G3SDW

    Ken G3SDW Moderator

    Well Paul its not the Smart meters, clear that on up first.

    With it being that strong, and AM is the best mode to use for interference problems such as this, means it is very local to you.

    You need to have a chat with either one or the other neighbours to see if they have had anything new recently, and i am assuming that this has started recently.

    Keep them sweet, don`t accuse as they will hold the key to getting your problem sorted, just ask for there help in solving a small problem, they will not have any idea that they are causing anyone any grief.

    You could narrow it down by doing some DF work with your 817 by keeping the antenna as small as you can and as the signal gets stronger reduce it some more until you can disconnect it altogether, you will then know you are on top of it, that way you will know what house to go too first.

    Keep in touch as i am always here to help at all times.
  3. Paul Selwood

    Paul Selwood New Member

    Hi Ken,
    Thanks for prompt reply.
    I think its been there for a long time and had not realised it as I remember these intermittant noise peaks on SSB in the Autumn of last year. Also it seemed as if I was a little deaf on MS, compared with other fairly local (within 10km) stations. I now realise that I am not "deaf" but that the AGC is being held on by this large signal that you don't really know about when in SSB mode. Then it got really bad just at the time a neighbour took BT Sports from BT. and I had started investigating. I did discuss it with him and went in with my 817 but all was quiet around the router. The interseting thing is that it does not beam up for max signal to close houses.see attachment showing peak signal. There does seem to be a possible element of main borne as it peaks up with a short whip on n 817 near mains or it could be that the whip is just coupling into the mains wiring and it is acting as anantenna for it.

    Think I will take a walk up the road after dark and see what I can hear.

    Attached Files:

  4. Ken G3SDW

    Ken G3SDW Moderator

    Yes Paul you are right when you say getting near mains wiring increases the noise and right in saying it just acts as an antenna.

    I get cases most days saying it is the phone cable or the mains cable that is radiating the noise but all to often it is something else.

    You are right as to the next thing to do a walk about can uncover all sorts of things, you will be surprised on what comes out of your neighbours houses, try not to get them mixed up with you noise.

    Just from memory and a great possibility is that someones is that it could be a cheap TV distribution amp going unstable, your symptoms have been known before for that.

    Although your neighbour does not seem to be the culprit then it may well come to a point that you will need to ask him if he could turn off his mains supply.

    Is this neighbour the one connected you you? as looking on google maps i see they still have the old band 1 and band 3 antennas on the stack, just a thought

    Let me know how you get on if you could.
  5. Paul Selwood

    Paul Selwood New Member

  6. Paul Selwood

    Paul Selwood New Member

    Ken, Tracked it down to detatched house next door. PLT's put in by BT I think. Which ties up with the changes he made and the introduction of the interferance. I have noted with careful listening I can actually hear it on 2M as well.
    No problems with the neighbour. He does really need these units and has agreed to hard wire them from his router and no cables will be visible in the house so that siuts the Mrs. Fix is simple 5M CAT5 cable and one hole in a hole behind a cupboard so it will not show and cable runs in the under stairs cupboard.

    I did not get model number etc today but would the EMC committee like to borrow these to make measurements? If so I am sure that could be arranged.
  7. Ken G3SDW

    Ken G3SDW Moderator

    Brilliant news Paul, once again the dreaded PLT devices rear the head once again, we dont see them very much theses days.

    My word you have a very sensible neighbour, that is a rarity today, bottle of wine and some chocs for the wife i feel lol

    If thats OK then we could take some measurements, especially if they give a problem as high as 2m, if yo look on QRZ.com them my address is OK there, and let me know how much the postage is and i will send you the QRK

    Thanks for letting me know, believe it or not not many do.
  8. Paul Selwood

    Paul Selwood New Member

    Hi Ken,
    Cable arrived for hard wire job today. With a bit of luck installation should be done tomorrow.
    I did ask if you could borrow the offending items for testing and the answer is yes. Because he is not likely to use them because they cause me problems.
    I will ship them off to you once everything is working OK.
  9. Ken G3SDW

    Ken G3SDW Moderator

    OK Paul, thanks for the update
  10. Paul Selwood

    Paul Selwood New Member

    Hi Ken,
    All the work is complete in the neighbours house now.
    I have the offending objects and will send to you today.
    Although I have done Ofcoms job for them I was thinking of sending in a complaint so that there is anofficial record of the problem. This being the case I was also thinking of waiting until they have been tested and sending results to them with the complaint as I suspect they will be out of spec.
  11. Ken G3SDW

    Ken G3SDW Moderator

    You can do Paul but to be honest you will be wasting your time, they will open a case and just close it and will not keep a record of it, which is a beef we have with them as they often say they do not have enough complaints to take action.

    As for the units then fine and thank you very much, just let me know what i am in your debt.
  12. Ken G3SDW

    Ken G3SDW Moderator

    One final thought, it will be interesting to see if your neighbour notices an increase in his download speed?

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