VHF interference

Discussion in 'EMC Matters' started by Andy M0RON, Jan 20, 2017.

  1. Andy M0RON

    Andy M0RON New Member

    Hi,
    In the last couple of weeks I have been experiencing strange interference on 2m fm. When no signal is being received no interference is heard however when a signal is received it is accompanied by a noise similar to a smps. I can walk up the road 20m either way from my house and the noise disappears so I believe it is coming from my house or my neighbours, I turned off power to my house but the noise persisted. During the day it was not noticed.
    To further muddy the issue, I had a power outage, only my house affected no one else, sub station fuses blew, upon reconnection to supply my electricity meter no longer has a display and has gone faulty, cannot be replaced until 7/2! I still have supply though, following this I now have a slight noise during the day. So until meter has been replaced I am not going to look for the source in my neighbours house, she is good as gold, in case it was my meter failing causing the noise.
    I have tried 3 radios and the noise is on all 3, ft 817, vx8de and a baofeng. Outside, in the back garden the noise on my yaesu vx8de and stock aerial, fm is unusable at night, same radio on my colinear up above the house is better but still not good, away from the house it is perfect. I have not tried hf yet as I have a lot of noise on hf anyway but will try this weekend.
    So my question is has anyone else experienced interference this way? Only heard when receiving voice on fm so far, am and fm broadcast unaffected. If received signal is S9+ no interference.
    I have recordings but the format is wrong for upload, mp4a so I will convert them and post later.
    Andy
  2. Ken G3SDW

    Ken G3SDW Moderator

    Hi Andy, thanks for posting on the forum.

    I think from what you have said then i agree with you waiting for the meter to be replaced, assuming that all of this started when you had the outage, at least when that is out of the equation then you can make the start to locate it, and from your comments when you monitored outside then i think it will be one neighbour or the other.

    Look forward to hearing the results when the meter is exchanged.

    73
    Ken
    G3SDW
    EMC Help Desk
    RSGB
  3. Andy M0RON

    Andy M0RON New Member

    Hi Ken,
    Just to clarify the problem started just after new year but then on the 17th January my fuses blew at the substation but not in the house, lights flickered for about a minute before losing supply, meter went out of service when supply was restored.
    If the meter was failing prior to 17th it may be the culprit but when my power was off at the fusebox the noise still persisted however the meter was still live.
    As said until the meter is changed I'll hold fire, too many variables.
    73
    Andy
  4. Ken G3SDW

    Ken G3SDW Moderator

    Yes Andy, thats all we can do as you rightly say to many variables.

    Will be interesting to see what it is but one final thing, can you confirm that when you lost all of your power your immediate neighbours did not, is that right?

    73

    Ken G3SDW
  5. Andy M0RON

    Andy M0RON New Member

    Hi Ken,
    Yes, I lost power but no one else did.
    Unfortunately I did not check if the problem was still there when I was off supply. If I had and the noise was still there I could be reasonably certain that I was not the source.
    During this morning there hasn't been a problem but guarantee tonight there will.
    73
    Andy
  6. Ken G3SDW

    Ken G3SDW Moderator

    Ah thats interesting, so your immediate neighbours did not suffer an outage but you did, not that it does not meant the others local to you did not suffer either, something similar happened to me many years ago.

    It is odd that you say that today so far it is not there pointing to it being possibly one of your neighbours and not your faulty meter after all.

    How well do you get on with your neighbours either side of you, good i hope as you may have to ask them at some point if they had something new installed just into the new year.

    When they come to exchange the meter then it will be a good idea to monitor on 2m when he takes the meter out of circuit, still til then just keep an eye on things and report back if you could.

    73
    Ken
    G3SDW
  7. Andy M0RON

    Andy M0RON New Member

    The meter is being changed this afternoon, my club holds a net tomorrow evening and will be a chance to monitor the situation and if interference present try 6m and 70cms as well. Will keep you posted.
    Andy
    M0RON
  8. Ken G3SDW

    Ken G3SDW Moderator

    Thanks Andy, look forward to hearing the results.

    73

    Ken
    G3SDW
  9. Andy M0RON

    Andy M0RON New Member

    Hi Ken,
    Well, as I said the meter was changed on 7/2 and was a direct like for like swap, the meter has a digital display, which had gone blank, but it is NOT a smart meter and does not send data back to my supplier.
    After the meter was changed I was able to approach it with an AM receiver and had no noise until I was very close, before I had noise in most parts of the house on AM. Reception on FM has reverted back to it's previous good quality with weak signals copyable.
    So it appears that it was my meter that was the problem. I suspect that a component was going bad at the start of the year causing interference and then finally gave up blowing a fuse in the substation, no one else's just my house affected. I carried out the advice to turn off the mains at the fusebox and thought that it wasn't me causing the problem as it still persisted however, as the meter is mains side of the fuse box it was still radiating noise. So I think that the moral is that even if the mains is off at the fusebox don't assume that the fault lies elsewhere.
    Thanks for the help and advice Ken and I hope that this little problem may help someone else in the future.
    73
    Andy
    M0RON
  10. Ken G3SDW

    Ken G3SDW Moderator

    Hi Andy, i am a bit confused.

    Are you talking about the smart meter "the meter has a digital display, which had gone blank, but it is NOT a smart meter and does not send data back to my supplier" so what is it, if it is not a smart meter, what is it there for, or are you saying that it is just your electricity meter with a digital display?

    At the end of the day your problem is solved that being the main thing.

    Finally when ever you go close up to any electronic device with an am radio then you will always get some hash pick up of some sort or other but that should not radiate very far at all.

    Thanks for the update and lets hope that you will be noise free for a long time.

    Always here to help at all times.

    73

    Ken
    G3SDW
  11. Andy M0RON

    Andy M0RON New Member

    Hello Ken,
    Yes it is just an everyday electricity meter with a digital display that shows information on how much electricity has been used. It is a dual rate meter and usually shows how many units of electricity has been consumed on rate 1, press the button next to the display and it then shows how much has been consumed at rate 2, there are further displays showing other information if the button is pressed again. The person who reads the meter simply records the displayed information shown on rate 1 display then cycles through to rate 2 records that information in his handheld unit and goes off to generate the bill.
    I suspect that an onboard component started to fail at the start of the year causing the initial fault and then failed completely taking the display with it. The strange thing is that it did not interfere constantly, only at night or early morning, presumably times of high demand. Also it only presented itself when I received a signal containing speech, if there was no speech there was no interference suggesting parasitic action. The radios used were battery powered, I am at a loss to understand how it latched onto a signal but that appears to be what happened.
    The meter is contained within an earthed metal cabinet and now is only heard if the meter cupboard door is opened, 30cms from the closed door, no noise heard, open the door and move the receiver closer and it can be heard but as you say it is to be expected.
    Anyway, the problem has been resolved satisfactorily.
    73
    Andy
    M0RON
  12. Ken G3SDW

    Ken G3SDW Moderator

    Great Andy, your problem as you explained is not uncommon as far as the radiation is concerned as odd sorts of RFI can be radiated by the mains supply cables wherever they maybe.

    Does not happen very much but as it happens i am dealing with a similar case at the moment where the radiation is coming from the supply wiring.

    Thanks for clarifying the situation, as so far we have never had a problem with smart meters not saying we will not in the future but i am sure the problem with your dual supply meter will not be the last one but hopefully not too many.

    Once again always here to help at all times.

    73

    Ken
    G3SDW

Share This Page