HF interference on my ring main?

Discussion in 'Interference Problems' started by M6VWM, Apr 1, 2018.

  1. M6VWM

    M6VWM Member

    Newly passed my foundation a week or two ago but as yet still haven't got on air properly due to HF interference. I have S9 or higher noise floor which makes all but the strongest signals impossible to read.

    I have an Diamond GZV 4000 (switching) 857d with LGD auto tuner and AV600 meter. I have noticed that when the problem is present my SWR is higher.

    Investigation so far:

    • Running rig with home as normal, s9 or higher noise on 10m through 40m (may be more but I dont have antenna for that)
    • Isolated mains supply entirely and ran off battery. Noise gone, as low as S1 but sometimes S4/5 at worst. Great to find out its at least inside my own house.
    • Put ferrites on all my cables and connectors, and a few cables I could access around the house. brought it down to S8 at best but still often higher.
    • Unplugged and switched off every item in the house one by one including fridge, shower, lighting, oven, plug sockets, powerlines etc etc. Nothing plugged or switched on at all still s8/9 +.
    • Isolated garage mains connection too, no change still s8/9+.
    • With everything off or unplugged, removed fuses one by one, identified ring main fuse as the one causing interference.
    • Appears to be the wiring itself?
    So I guess the question for me is what next? It seems to be my mains itself and specifically the ring main. With nothing plugged in or switched on but the fuse in place I have S9, so how to I work out what it is to resolve it? Could it be the wiring itself? Or is it likely to be a socket or switch? Is there anything I could try? Are filters worth considering or are they snake oil? The house is an 80s one so I assume will have PME earthing.

    Disheartening start but I am hoping to get it resolved and get my first contacts soon :) Any advice appreciated.
  2. M6VWM

    M6VWM Member

    Should say VHF/UHF seems fine.
  3. Ken G3SDW

    Ken G3SDW Moderator

    Hi Mathew, thanks for using the forum.

    Well you have gone about it the correct way by turning off your mains supply proving that it i coming from your own house.

    You say that once the supply is back on then the noise is there and turning off all individual item does not take it away.

    This only means that there is still something plugged in.

    1. Central heating boiler.
    2. TV distribution amp, sometimes in the loft
    3. Outside security lights.
    4. Cooker, sometimes permanently wired in.

    But a god mad little apples there is still something permanently on, your house wiring will not emit noise and for filters then no as you dont know what it is so how can your filter it.

    Give it some careful thought and you will find it as its there hiding.

    Let me know, i am always here to help and between us we will get to the bottom of your problem.
    M6VWM likes this.
  4. M6VWM

    M6VWM Member

    Thanks Ken appreciate your advice. Great points.

    • I did turn off the central heating on the combi boiler, this has a Hive setup which I suspected too, but I disabled it with no change. It's on its own fuse too which didnt seem to change the signal.
    • The Cooker on the it's own fuse but has an isolation switch which was off, that one is off the list too I suspect. This has made me think about the cooker hood extractor fan. Ill add that to the check list as I am not sure which fuse this is on.
    • Dont have any security lights on the mains at the moment so hopefully that can be eliminated.
    • TV amp, I don't think I have one but I could indeed have one in the attic without realising. I will take a look in the attic tomorrow and see if there is anything there.
    Many thanks,

    Matt.
  5. G3OYU

    G3OYU New Member

    Hi Mathew
    One thing you apparently haven't done is to leave all the house electrics switched on anad then run the rig from a battery - is the interference still there?
    As Ken has said clearly you have something on even though you have turned off each individual item, this is proved by the problem going away when you kill the incoming mains supply. I agree with Ken the wiring cannot cause interference, it can pick it up however, but of itself no.
    There is one problem that you may not have here but it is worth a try. Some years ago, in my work capacity as an electrical inspector, I was asked to trace a fault in a house where the owner wanted to change the light fitting in their lounge but were unable to turn off the supply to the fitting by removing the fuse for that circuit. It turned out that a wiring error in the lighting circuit had an unknown loop that was fed by 2 fuses, so removing one fuse at a time did not remove the problem. This might give you a possible route for futher investigation, remove a fuse, check for the noise, then remove a second fuse without replacing the first, keep removing fuses without replacing thos already out, this might narrow down your problem.
    As Ken said keep us up-to-date with progress as the more information you give the better able we may be to point you in the right direction.
    73
    Brian G3OYU
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  6. Ken G3SDW

    Ken G3SDW Moderator

    First of all Brian, If you check then Matt has said he has turned off his mains supply and used his rig on a battery with no change.
    Matt OK then I am sure you have more than one TV in your house and if that is the case then there will be a distribution amp somewhere normally in the loft.
    Another way is to go through each circuit breaker to check which circuit it is on that way you can isolate it down to one part of your house.
    73
    Ken
    G3SDW
    EMC Help Desk
    RSGB
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  7. M6VWM

    M6VWM Member

    Morning gents,

    I have indeed ran from battery with mains on and removed them all and one by one. It does seem to be on one fuse. It that fuse is upstairs and down it seems.

    I’m going to get some batteries for my LW radio today and have a scout the attic for a tv amp and also check out the kitchen extractor which seems to be in the same fuse too.

    Many thanks,

    Matt.
  8. M6VWM

    M6VWM Member

    Only one tv but the previous owners had two.
  9. Ken G3SDW

    Ken G3SDW Moderator

    Hi Matt, thanks for the update, at least you have isolated it to one part of your house, that will make it easier to find.

    With the fact that in your case it is within your own house then the thing to remember is not to try to go too deep, in many cases it will be staring you in your face.

    If the previous owner had two TV`s then if it was done in the correct way then he must have had a distribution amp with the most common place being in the loft, the best way to locate it is to follow the antenna lead to see were it goes, if there is indeed an amp somewhere then that will leed you too it

    As for the extractor fan then that is unlikely to be the problem but once you have found the culprit then get back to me and we can advise on how to stop it from radiating all the noise that you have.
  10. M6VWM

    M6VWM Member

    Searched attic no amp found but a splitter with a cable connected and nothing on the end of it, just bare wire. Removed it and this seemed to have taken me from s9 to s8 surprisingly.

    Ran around the house with an old lw radio checking. Seems to all come down to a double socket in the lounge which seems to create the noise if anything significant is plugged into it. Could a loose connection in there cause this? Or perhaps something else? Some things can be plugged in with no issue but the diamond gzv4000 or any multi plug and the noise appears.

    The diamond psu has a schuko adapter with earth as it came with a euro plug.
  11. Ken G3SDW

    Ken G3SDW Moderator

    No doubt some if not all the cables in your house are re-radiating this RFI so any redundant ones should be removed.

    This double plug you have mentioned, do you mean that when nothing is plugged into it then you have no noise on your rig?

    You will need to make doubly sure that your PSU is correctly earthed by cutting off the Schuko adapter and replacing it with a 13amp plug and checking continuity of the earth connection to the casing of the PSU, not saying this will sort the problem out but for safety this needs to be done using a multi meter.

    Have you got any power to your garage, if so is there anything out there that could be a problem as at the end of the day there is something withing your home generating this RFI, you may well have two items causing the same problem, this can often be the case.

    We will get there but all to often things like this take a little while to get to the bottom of.
    Last edited: Apr 2, 2018
  12. M6VWM

    M6VWM Member

    Yes when plugs are removed from the double socket, the noise vanishes, another socket in the hall has same effect.

    The schuko is an earthed Europe to Uk adapter with 13a fuse, but I didn’t want to cut the plug off until I’m sure it’s working correctly as it’s new. Thought it maybe the psu but plugged in in the next room no issue.

    I do have power to my garage but isolating the garage didn’t seem to change anything.
  13. Ken G3SDW

    Ken G3SDW Moderator

    So what items are you plugging into the socket you have mentioned?

    Do they cause the same problem when plugged into a socket in another room?

    When the noise is there what happens when you unplug your PSU and run your rig off of a battery?

    Regarding the mains connection to your power supply can you find another lead to try as it is only a kettle plug.

    Clutching at straws but it's getting that way but we will get there all be it slowly.

    73
    Ken
    G3SDW
  14. M6VWM

    M6VWM Member

    I’ve been running the radio on battery for all tests.

    If I plug the psu into the double socket I get noise, any multi plug plugged in here also creates noise. Same effect with close by hall socket. Effect seems worse if multiple items are plugged in.

    Plugged psu in in the kitchen with radio still in lounge, no noise. Psu cable on gzv 4000 is hard wired sadly so can’t change it. :(

    Tried psu further away from rig in same room still had noise. Ferrites also on power cable no real change.

    Unplugging psu or anything on double socket whilst on battery the noise drops away completely.
  15. Ken G3SDW

    Ken G3SDW Moderator

    Is there anyway that you could borrow another PSU just for a quick test.

    Just would like to isolate it out of the equation.. as it is the most likely candidate.

    73
    Ken
  16. M6VWM

    M6VWM Member

    I’ll ask around and try it thanks
  17. Ken G3SDW

    Ken G3SDW Moderator

    OK Matt, we need at this point to isolate things as it seem to be in the frame at the moment.

    If we don't we could go around in circles and that would not get us anywhere at all.

    73
    Ken
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  18. M0JAV

    M0JAV Moderator

    Do you have a burglar alarm or mains operated doorbell?
    John M0JAV
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  19. M6VWM

    M6VWM Member

    Morning John and Ken,

    It's like nailing jelly to the wall haha, just when I think Ive sorted it I realise I havent haha.

    I do have door sensors via a hive systems but they are battery powered and removing them didn't seem to make a difference to the noise levels. Also powered down the hive system completely but again no discernible difference.

    I do have a wireless doorbell, again on battery, so I will try removing the batteries from that and see if it helps.

    Struggling to find another psu for testing quickly so I may just try moving the radio to another room entirely.

    Weirdly I did a power off, walk around with my house with an old LW radio. I found two two huge hot spots on the wall (I live in a semi) where the noise was horrendous I can only assume from next door. Interestingly I have a extension lead that sits right by one of these hot spots. I noticed weirdly that plugging in the PSU here even with the end plug unplugged (i.e. no power) increased the RF. Could my extension lead be picking up next doors RF through the wall and radiating it inside? New to all this but was very surprised to see an increase in RF on an unconnected power cable.

    Confusing stuff.
  20. M6VWM

    M6VWM Member

    Of course I could be imaging it lol and its unrelated.

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