HF Interference

Discussion in 'EMC Matters' started by NikRead, Jun 23, 2017.

  1. NikRead

    NikRead New Member

    HI.

    A few weeks ago interference started to my HF set up.
    The Noise here has gone up in the last couple of years due to new neighbours but this particular interference is seriously bad..
    From an s2 noise floor at 8.500Mhz, at 8.502MHZ it jumps to s9 to +20 this continues up to 11.995Mhz when the noise floor abruptly returns to S2.
    It is there 24hrs 7 days a week, I have turned the power off in the house and used a portable radio to try to DF it with no joy yet.
    [​IMG] [​IMG] [​IMG]

    Has anyone any ideas please..

    Many thanks.

    Nik,
    M5DND
  2. Ken G3SDW

    Ken G3SDW Moderator

    Hi Nik, is there specific reason why you mention the frequencies you have ie 8.55Mhz to 11.995Mhz as the only amateur band is 10Mhz so assume that you use that band.
  3. NikRead

    NikRead New Member

    Hi Ken, Yes I did use 10mhz but cant now due to s9+20 of white noise.
    I should have said that the noise is white noise..


    Nik
  4. NikRead

    NikRead New Member

    Ken, I will also add, that the noise only effects the frequency range is gave I.E. 8.502Mhz to 11.995Mhz

    Nik
  5. Ken G3SDW

    Ken G3SDW Moderator

    Well you have done all you can, initially that is.
    Now comes the hard bit, you will need to talk to your immediate neighbors to see if they have had something new installed recently, if so no doubt it will have some sort of SMPS attached to it.

    Hope that they are cooperative as with out them we are lost.

    Update us as and when, always here to help at all times.
  6. NikRead

    NikRead New Member

    Will do Ken.. One set of Neighbours have been hear a long time and are fine and understading/helpful but either side of me new people.. Should be fun!!!
    The Noise is strange as I have seen anything about this before..

    Thanks,
    Nik
    M5DND
  7. Ken G3SDW

    Ken G3SDW Moderator

    Softly approach is the key Nik, but i am sure that they will not have any idea that they are causing any problem, just ask for there help in solving a problem.

    Good luck and update us when you can.
  8. Mike G3ZCC

    Mike G3ZCC New Member

    Just a thought Nic, do you have a portable such as an FT 817?
    Even with its rubber duck antenna you should be able to deduce where the interference is at it's strongest.
    Is the noise on any other bands?
    Mike
    G3ZCC
  9. Ken G3SDW

    Ken G3SDW Moderator

    As Nik has said Mike its s2 on all the bands except from 8.5-11.995Mhz where it is s9, you advice is the correct thing to do and looking at his QTH then he is not in a very built up area and feel it is close to home, just take a look on QRZ.com
  10. Martin G0HDB

    Martin G0HDB New Member

    Nik:

    From the frequencies you mention the cause of the QRM to your reception will almost certainly be someone's VDSL service - do you know if any of your neighbours have recently changed to 'superfast broadband'?

    VDSL2 in the UK uses various frequency bands in the range up to 17.664MHz; the Uplink 2 band is from 8.5 to 12.0MHz which tallies exactly with what you've observed. U2 is one of the bands that transports data from the subscriber, ie. you or your neighbour, back to the DSLAM in the exchange or the nearby cabinet. If any of the wiring, especially within the premises, is electrically imperfectly balanced then the VDSL signal on the line radiates (when it's not supposed to) and causes exactly the QRM you've observed. I suffer from exactly the same effect here at my QTH at the aforementioned transition frequencies - the noise floor is raised by about 15-20dB between 8.5 and 12.0MHz, thus making the 30m band all but unusable.

    The VDSL signal can radiate from the BT overhead 'dropwires' if you've got those providing the phonelines in your neighbourhood, but if someone has self-installed some extension wiring in their house and then connected their VDSL modem/router to the end of the extension then it's very likely that the unwanted RF emanations are being caused by imperfect electrical balance in the extension wiring.

    If you can approach your neighbours you could ask them if anyone has recently 'upgraded' to superfast broadband such as BT Infinity. If they have, then you could ask them to try turning off their BT Home Hub or whatever and seeing if the noise disappears. You could also try transmitting a few Watts of RF on the 10MHz band, ideally just outside the suspect premises, and seeing if there's any change to the noise - you might find that the wide bandwidth noise disappears and is replaced by a comb of carriers 4kHz apart - these are generated when the VDSL connection goes into a training mode because of interference (such as your 10MHz transmission!).

    In any event I would urge you to report your interference to John Rogers M0JAV, he's the Chairman of the RSGB's EMC Committee and is collecting as much information as possible about VDSL interference to amateur-bands reception so adding your case to the list will provide even more ammunition with which the RSGB can tackle Ofcom and BT about this scourge.

    Let us know what you find and if you make any headway in getting the problem remedied.

    73
    --
    Martin G0HDB

Share This Page