80 meter QRM.G3LEO.

Discussion in 'EMC Matters' started by g3leo, Jul 9, 2019.

  1. g3leo

    g3leo New Member

    SInce moving QTH 4 months ago I have been experiencing continuous interference on 80 meters 24/7.It is pulsed RFI between 3.570mnz and 3.690mhz at a repetion rate of 2 per second with a maximum magnitude at 3.620mhz which is 6s points above the 3s point background noise level.
    It is not present on any of the other HF bands though it is also audible at about 3.450mhz narrow band.Also there is an increase in background noise level from 3.80mhz upwards again of 6s points above the 3s point background.
    My QTH is one of 5 on a small estate each of which is fed with a seperate overhead phone line about 100 yards long from the same pole which is fed fron an underground cable at least a mile long.When I walk under the phone lines with a battery portable tuned to 3.620mhz the the interferance can de heard clearly.
    I am most concerned with the pulsed rfi centred on 3.620mhz.and wonder if anyone else has come accross it and has any thoughts as to the cause.
    My station is a Trio 830s and a G5RV located in a small village in North Yorkshire.
    Hears hoping! Gerald Brigham, G3LEO.
  2. Stevie Gillespie

    Stevie Gillespie New Member

    Hi Gerald..
    I like you have a very bad/serious issue on 80m's also with noise..
    On 3.656.4MHz I get a solid signal 5/9+ 25-30db noise spike and it has caused massive qrm on 80m, 40m, 20m but the higher I go above 20m the less the noise issue is.
    I tried to upload a short video and picture of it to show you but the site won't accept it.
    I hope you can get your issue resolved and would be grateful to know what caused it if you find out.
    vy73de MI0GTA
    Stevie
  3. Ken G3SDW

    Ken G3SDW Moderator

    Right guys, as it seems that no one else wants to try and help you then i will try to help myself, but fist of all what have you done so far to try to locate were the RFI is coming from.
  4. g3leo

    g3leo New Member

    Many thanks Ken for your help.
    I have done the following:-
    1. Found the interferance on my trio 830 s.
    2.Tuned battery portable to the pulsed interferance.
    3.switched off power to my house.
    4.Walked under the phone lines with the battery portable with power off my house.
    5. When doing so can hear clearly the pulsed interferance.(it sounds like an electric fence but confined to one frequency)
    6.As new to the location have not been brave enough to tackle the owners of the other phone lines.
    7.Am thinking of asking OFCOM to investigate if no other suggestions.
    Best wishes, Gerald. G3LEO.
  5. Ken G3SDW

    Ken G3SDW Moderator

    Hi Gerald, well first of all at this stage do not get in touch with Ofcom as you will find them very difficult to get them involved.

    In most cases with symptoms such as your then the most likely item causing your problem is an SMPS in standby mode, but as you say it could be an electric fence, this being the case then i assume that you live in a rural area.

    It could well be coupled to an item that has a connection to a land line, many items do.

    You will need to locate roughly which house or field it is coming from and approach them with caution, not appearing to accuse them in anyway as this often offends.

    Just ask them if they could assist you to try to solve your problem and if you can let then hear it for themselves.

    Dont rush just take your time as RFI problems are not solved over night

    Good luck and shout if i can be of anymore help

    73 Ken
    G3SDW
  6. Ken G3SDW

    Ken G3SDW Moderator

    Gerald, have just been looking at your location and now see that you are very rural indeed so your fist assumption about an electric fence may well be right but still worth talking to your immediate neighbors which there appears not to be to many
    73
    Ken G3SDW
  7. g3leo

    g3leo New Member

    Dear Ken,
    Many thanks for your most helpful reply and I was very interested in your suggestion concerning the SMPS in standby mode.What does the interferance it causes sound like? Is it similar to mine which is pulsed at a PRR of 2/second centred on 3.62Mhz and extending 500hz either side with a maximum signal strength of S9?
    As this has been present all the time since this Feb. When we moved house,day/night 24/7. I do not think it is the cause.If indeed something is getting onto the overhead phone lines from the houses they serve then it would need to be on all the time.I cannot think of anything else in a private house which could cause such specific interferance as I am hearing. This leads me to believe that it is coming from the exchange rather than from the houses it serves.As I mentioned in my first posting I am also hearing a large increase in noise at 3.80 Mhz extending upwards in frequency of S9 magnitude which I understand is is to do with VDSL. If so the pulsing centred on 3.62 Mhz which is causing me problems may also be connected with VDSL.
    Therefore I think my only option is to get in touch with Ofcom and try to work with them to see if the interferance is comming from the exchange and if so what can be done.
    Best wishes, Gerald, G3LEO.
  8. Ken G3SDW

    Ken G3SDW Moderator

    Ofcom will only get involved if they feel that your problem is what they class as harmful, and from your description they will just close the case, things are not the same sadly as they were many years ago.

    Your increase in noise at approx 3.8Mhz (3.79Mhz) will no doubt be attributed to VDSL but the pulsing at 3.62Mhz is very unlikely to be that, two separate items i feel.

    SMPS in standby mode can be the problem and because it has been there for some time is not a reason to dismiss that as in the past on several occasions it turns out to be a charger in an out building for either a golf buggy or a disability scooter, both had been disconnected but not from the mains supply.

    Over head phone lines can carry RFI in all shapes and forms as they are just acting as a very good antenna at LF frequencies, by walking close to them will always increase the signal level of your portable RX and the interference you have mentioned ie pulsing type is exactly what a SMPS in standby will sound like, the fact that is is of the strength you have mentioned,S9, then it is very local to you.

    You will need to talk to your nearest neighbor at some point if you want to get this one put to bed.
    73
    Ken G3SDW
  9. g3leo

    g3leo New Member

    Dear Ken,
    I think I misled you when I mentioned electric fences in my previous posting. The interferance they cause is pulsed at about 2 to 3 per second extending over many MHz and is picked up directly rather than by radiation from overhead phone lines.
    What I ment to say is that the pulsing sounds similar but unlike an electric fence ,the interferance I have is confined to a particular frequency,3.62Mhz.,and is picked up fron the the phone lines.
    Beat wishes,Gerald,G3LEO.

    pulsed
  10. Ken G3SDW

    Ken G3SDW Moderator

    OK fine Gerald all understood, but one thing you need to understand is that when you go close to phone lines then because the interference increases then that does not mean that is is coming from the line, or something connected to it, but the line is just acting, and coupling, to the portable RX`s antenna, making the RFI sound louder giving you the impression of it coming directly from something connected to it, not always so.

    If what you are saying that the line goes directly to one property then i think you should at least give them a visit and ask for there help.

    What you must understand regarding Ofcom is that even if they did call, which is unlikely, then they may agree that there is a possibility that it is coming from whatever property at all then that does not mean that the owner of that property has to cooperate, Ofcom have no powers to force them to do so.

    Try Ofcom if you like but be prepared to have to prove that your problem is harmful, thats not easy as they will say 1. Dont use that frequency and 2. Use another band, this is how they work regarding us as radio amateurs today, long gone are the days of the PO and RA who did get involved with us and had powers to enforce action to offending equipment.

    73 Ken G3SDW
  11. g3leo

    g3leo New Member

    Dear Ken,
    Again thank you for your two most recent postings which were so helpful.
    You may wonder why I am so interested in 3.620Mhz. It is because 3.615Mhz.is the VMARS frequency on 80 used by about 500 amatures interested in valves and older military /amature equipment to try out their sets on air mostly using AM. I am an early member,nearly 20 years standing,and since moving qth cannot join in as I used to due to the interferance.
    The most important thing you have told me is that the type of interferance from an SMPS on standby accords with what I hear. This gives me a clear idea what I am looking for and hence the confidence to approach a complete stranger, my new neighbour,and ask him if I can search his house.
    I will let you know what I find in due course.hope I have not taken up too much of your time over this but I can assure you I have learnt a lot and it has been most valuable for me.
    Beat wishes, Gerald, G3LEO.
  12. Ken G3SDW

    Ken G3SDW Moderator

    Not at all Gerald, this is what I do so it's a pleasure to help.
    Will look forward to what comes up when you approach your neighbour.
    As for all the other points you mentioned concerning the frequency you want to use on 80m then I did do some searching on your call sign and what you are involved with which I found very interesting.
    73
    Ken G3SDW

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