Spikes on all bands - help identifying where to look

Discussion in 'EMC Matters' started by trevor clapp, Aug 18, 2019.

  1. trevor clapp

    trevor clapp New Member

    I have recently being getting pulsing interference on pretty much all bands and have narrowed it down to a general direction after powering off everything and wandering around with a makeshift antenna on the KX3. But I'm not sure what I am looking for now.

    Much stronger on the beam (3ele StepIr) as opposed to the BigIr vertical

    The general direction (found by using the beam and the wander method) has a LEB substation and a house or two. So I suppose the question is is there a resource where one can look at screen shots of various types of interference to try and match them up and/or does anyone have any suggestions as to where I should be looking next or what I need to do to pinpoint the source

    . MØTDZ Noise - 1.jpg MØTDZ Noise - 2.jpg MØTDZ Noise - 3.jpg MØTDZ Noise - 7.jpg MØTDZ Noise - 8.jpg

    Here is a location plan from google earth, funnily enough the beam is pointing in the rough direction ! Screenshot 2019-08-18 at 14.30.18.jpg
  2. Ken G3SDW

    Ken G3SDW Moderator

    Trevor, you have gone about this in the correct way to start with and thats great.
    I do not think that looking to try to match up with similar screen shots is the correct way to go, it will not locate were it is coming from.
    Thats the next step so do what you did before, use your portable RX with your make shift antenna until the signal level gets very strong and once it has take the antenna off and at that point you will find it much easier to home in on its exact location.
    You say "Pretty much on all bands" can you give some indication of what bands and at what strength, as you only show 40/20 and 17m in your screen shots

    Speaking in general most problems of this type can be put down to electric fences due to poor connections thats due to wet days and we have had quite a few recently, arching when breaks have occurred and the owner just twists them back together, very common indeed.

    Give it a go and let us know how you get on but at some point you will have to knock on someones door which has to be done very carefully.
    73
    Ken G3SDW
  3. trevor clapp

    trevor clapp New Member

    Brilliant Ken and I did a double take as we have just replaced our electric fence energiser but a quick investigation shows ours doesn't show up on the panadapter but you can hear the pulses close to it. They don't tie up with those that I am seeing. Now i doubt the neighbors have chickens but I agree that the pulsing nature seems to tie in with the same sort of frequency of pulse that we get from our fence. So that is something to go and look for.

    Band wise it is strongest on 20m +20dB ,less so on 17m = S9. 30mjust barely noticeable (but I have don't get good performance on 30 anyway for some reason) 40m = S9+ again. The panadapter in the pictures is quite accurate when read against the meter readings.

    So onward and upwards more sleuthing required. I will also get up at some odd times in the night to see if it is there. The main problem I am having is that it really needs a high gain antenna to pick it up which is a bit tricky when trying to walk around. The best success I had was with my buddipole and a loaded 20m dipole - Lots of odd looks as I walked up and down the street!
  4. Ken G3SDW

    Ken G3SDW Moderator

    Trevor, basically if it is a fence then depending on the length of the wire will depend on the signal level on what ever band it is giving a problem too, the wire is only acting as an antenna radiating the RFI.

    If you think there could be others local to you then these need to be investigated.

    If the RFI is local to you and it sounds that it is then it should be easy to locate, try going at different angles to cross reference it, ie go well past it when it is at its strongest and go on and till it gets weaker then go back again, its all trial and error

    73
    Ken
    G3SDW
  5. M0JAV

    M0JAV Moderator

    I agree with Ken it looks like an electric fence although it could be something in the substation. Now you have a good spectrum of what you are looking for then using proximity location as Ken says will find it faster than anything else. I am assuming the source is close by.
    If you want to see some traces of other users of the radio spectrum there is a database sigidwiki https://www.sigidwiki.com/wiki/Signal_Identification_Guide
    This is mainly a database of different types of known signals with a few RFI sources. It is most useful for identifying real signals causing problems but perhaps if more RFI signatures get added it could be more useful.
    Good luck with hunting down your problem.

Share This Page