VDSL....or not?

Discussion in 'Interference Problems' started by 2E0OPQ, Aug 13, 2018.

  1. 2E0OPQ

    2E0OPQ New Member


    I've only been active since late 2017, so I'm not that experienced - please be gentle :) Just got the 2E call last week.

    I have about S7 noise from apx 1.3 to 18MHz. I've listened online to serveral examples of interference (PLT etc) and none fit the bill. It's just 'noise'. It's present on both my OFCD and wellbrook loop.

    I've powered down the whole house and robbed the car battery - no effect, and have been trying to DF with an VR500 and improvised loop.

    After chasing ghosts and getting absolutely nowhere. I stood directly underneath my neighbours phone line (flies over garden), and it appears that is the source.

    But so is my line (other side of house), it's exactly the same, even with VDSL modem disconnected.

    However, I can't find any evidence of the VDSL guard bands from either my main rig or scanner in the garden.

    What else I can do to narrow it down? I'm sure my "loop and scanner" isn't the most sophisticated equipment. I did have an issue with my transmissions knocking out my internet connection, but that was resolved by using the old BT supplied NTE instead of a cheap VDSL modem. However, I didn't see any 4KHz spaced retraining carriers at the time (FT-991A waterfall).


  2. Ken G3SDW

    Ken G3SDW Moderator

    Hi Matt, this is what you need to know about identifying VDSL.

    The EMC Committee is carrying out an investigation of the significance of interference to amateur radio from leakage from VDSL systems. The emissions from VDSL are continuous and indistinguishable from white noise and may go unnoticed.
    VDSL2 covers frequencies up 17.66MHz. The downstream and upstream bands alternate and the easiest way to detect VDSL is to look for the change in noise level at the band transitions. These are nominally 0.138MHz, 3.75MHz, 5.2 MHz, 8.5 MHz, 12MHz, and 17.66MHz. The band that predominates depends on distance of the house from the street cabinet. Most problems are seen when the connection to houses in the area is by overhead cables.
    The effect will be that received signals seem weak and the background S meter reading higher than expected. To check for VDSL emissions tune about 75kHz either side of the nominal transition frequencies. Ignore off air signals and local incidental noise. Tuning around these frequencies and listening while watching the S meter will show a noise step if there is VDSL interference. If an SDR is available the step will be clearly seen and the 4.3125kHz patterning of the VDSL signal may be visible on a waterfall display, but careful adjustment of the contrast may be required for this.
    If you want to see some examples look at the 2014 RSGB Convention paper http://rsgb.org/main/files/2013/10/2014-Convention-EMC-paper-emerging-threats-v5.pdfThere is also an item on VDSL emissions in in EMC Matters in RadCom December 2013.
  3. Ken G3SDW

    Ken G3SDW Moderator

    Right Mat, you mentioned your neighbour, it could be VDSL or maybe just a very noisy SMPS that he has connected to one of many devices, we all have them.

    Are you on good terms with him, if so why dont you ask him to do the same as you have done by turning off his mains supply whilst you check your portable RX, let him hear for himself what you are getting, but what ever you do dont accuse in any way, it just put there back up as they have no idea what they could be doing.
    Always here to help at all times.
  4. 2E0OPQ

    2E0OPQ New Member


    I am on good terms and can just mention something slowing down our broadband. Have to find out if he has broadband first though :) But it is on my line as well, on the other side of the house.

    I've blown the dust off my QS1r SDR. Nothing really conclusive but below are the most interesting ones. I may have to play some more with the wellbrook loop.

    I can spot an apparent change on 3.75, but not on any other guard band mentioned.

    Thanks in advance,


    3750.JPG 8500.JPG
  5. 2E0OPQ

    2E0OPQ New Member

    And thanks for the quick reply :)
  6. Ken G3SDW

    Ken G3SDW Moderator

    No problem Mat, thats what i am here for.

    As i said it could well be just a very noisy SMPS and considering what any of them are connected too then then as well there will be a phone line, this will have the noise induced into it and then re-radiate it just like an HF antenna.

    If it is strong then it will most likely be very close to home, possibly your neighbour and if he is OK as you say then before you do anything else get him to turn off his mains supply, if it goes off then put it back on and go through each plug in SMPS, there maybe many, and you will come across the noisy one.

    If the parameters of what i sent you do not fit then it is most likely to be a SMPS, they often get mixed up.

    Let us know how you get on.

    Were about`s in the UK are you out of interest?
  7. 2E0OPQ

    2E0OPQ New Member

    Hi, North West Manchester and I'm a mile from the FTTC cab. If it's not my neighbour then I may have a problem as 10 other properties go to 'my' pole. Oh the fun :) When I was DF'ing it seemed that it was either coming from the pole or my neighbour. Sometimes...... That's when I decided to start "looking up".
  8. Ken G3SDW

    Ken G3SDW Moderator

    You need to take one step at the time Mat, check out your direct neighbour first, if not him then get back in touch and i will help you take the next step.
  9. 2E0OPQ

    2E0OPQ New Member


    The neighbour, surprisingly, let me power down the whole house!!! Suprised at that. Bad news is no effect, noise still there - putting my scanner near their phone socket (unplugged from phone socket), the same noise was still present there as well.

  10. 2E0OPQ

    2E0OPQ New Member

    Ah, also, from where the main line comes in, it is split - one leg is proper phone cable, the other is speaker/bell wire i.e. not twisted pair. The VDSL modem was plugged into it, but killing the power to the house made no difference to noise from it.
  11. Ken G3SDW

    Ken G3SDW Moderator

    OK Matt, well that eliminated that and thats the only way to do it.

    Going close to any phone line will give you increased noise, it just acts as an antenna being better than the one on the scanner, thats not to say that it is not connected to the source of the problem.

    What you need to do now is do a walk about with your scanner and see were the noise peaks, once it get stronger reduce the the antenna to a point that you can still here the noise with no antenna at all, then you will be on top of it.

    Let me know how you get on.
  12. 2E0OPQ

    2E0OPQ New Member


    Will do. But even with the aerial fully retracted I can hear it 50 yards away so it must be one hell of a PSU :) Also, finally got my new call updated on the system.

    Annoyingly, the loudest point seems to be under the pole. But that's a symptom, not a cause.

    Will keep on walking :)


  13. Ken G3SDW

    Ken G3SDW Moderator

    Some can be Mat, and from what you have said so far it will be something like a router and they have SMPS connected to them and the router will be connected to the phone line.

    These problems are not so easy to locate, they take a little extra time but with some patients you will get there, if all your neighbours are as helpful as your direct one then you will not have any problem, may take a while but you will get there.

    Sadly there is no magic answer, wish there was which would make my job a whole lot easier.

    Keep in touch.
  14. 2E0OPQ

    2E0OPQ New Member


    Well, I now have it narrowed down to two houses, with one the prime suspect (for the simple reason the noise on it's line is the loudest). I used my loop to narrow it down, wasn't having much luck reducing the antenna.

    My immediate neighbors I know, this house is half way down the street. Door to Door salesman I am not, so need to think about my pitch without them thinking I'm trying to nick their car hehe :)

  15. Ken G3SDW

    Ken G3SDW Moderator

    OK Mat well done for getting this far.
    When you approach them just ask for there help in solving a problem, let them hear what you are getting but as I said once before never accuse in any way at all, just choose your words wisely.
    Good luck and keep in touch
    Last edited: Aug 23, 2018
  16. Ken G3SDW

    Ken G3SDW Moderator

    Hi Mat, just wondered how things are going and wondering if you have any conclusions as i am in the middle of writing up my bi monthly report?
  17. 2E0OPQ

    2E0OPQ New Member


    As for technical conclusions, nothing yet. I have to approach first and am trying to find someone we know in common. I just think myself standing there with a radio will result in a call to the mental health hotline :)

    In the interim, I looking at using the wellbrook loop as an separate RX antenna for the simple reason I think this will become a game of whack a mole. So I can only minimise.
  18. Ken G3SDW

    Ken G3SDW Moderator

    Think that's a bit over the top.

    The company concerned know the score but are hopping you will go away.

    Although we both know that Ofcom and or Trading Stanards will not take any action so it might be a good idea to mention that you are going to get them involved.

    Give it some thought as it is you and only you that is getting the RFI which is stopping you excercising your right to your hobby

    73 Ken
  19. 2E0OPQ

    2E0OPQ New Member

    Over the top??? Confused as to my mind the company is in China somewhere making PSU's without filtering etc, but advertising otherwise.

    I still intend to approach the house, and it's not their fault - they have no way of knowing. Allowing someone you don't know into your home, with some sort of 'tech', is a bit of an ask these days.
  20. Ken G3SDW

    Ken G3SDW Moderator

    "The mental health hotline", deal with the importers suppliers and installers as they are responsible for putting it into service and on to the market.

    But i will leave it to you as you seem to have everything in hand, the details of your case will be submitted to the EMCC shortly.

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