VDSL Emission Investigation

Discussion in 'Investigations New Technology' started by Robin, Nov 20, 2014.

  1. G4LNA

    G4LNA Member

    I have just sent this email to John.

    I'm losing the will to live with all this malarkey, I feel like going outside and falling on my sword.

    Just kidding :D

    But seriously, if this keeps on I have got a new hobby and if this interference isn't sorted I will devote more time to that and put the radio in a box in the garage and turn the shack into a utility room, because I can see no end to this at all.
  2. John Stephenson

    John Stephenson New Member

    The matter of fact is THE RSGB AND OFCOM HAVE NO POWERS TO GET OPEN REACH TO SOLVE THIS PERIOD. My mate has been off the air moths now because of it was told itll take a few months to look at it well them few months has come and gone and still no further forward and a certain person isn't replying to his emails asking for an update. Our RSGB memberships are due for renewal and its certainly looking like they wont be renewed
  3. Ken G3SDW

    Ken G3SDW Moderator

    John i have asked John Rogers M0JAV to reply to your comments.

    He is, as it happens, doing a lecture of the findings of the VDSL survey at the RSGB convention this week end, so i am sure he will reply to you as soon as he gets back home.

    Finally John, maybe you could kindly let me know what your mates call sign is and of course yours as well, as it is nice to know who we are talking too.
  4. M0JAV

    M0JAV Moderator

    M0VHC Tom sent his form in mid July. We have not had any reports back from OPenreach since mid August. I have discussed this with Openreach as there have been some staff changes and we need to get some new people assigned to the task of area line balance checks.
    Following on from our VDSL survey conducted in September there could be 500 other sites to check and we need to agree with them how they handle this as there current capacity appears to be only a couple per week.
    I will post the slide show I am giving at the convention early next week.
    It shows a lot more cases than even I expected and most people did not realise they had a problem before looking for noise changes at the band edges.
    We have also been mapping the levels using an automated drive by system which has revealed more surprises in the extent of the problem.
    We now have more results to try once again to get action from Ofcom and Openreach.
    John M0JAV
    Chair RSGB EMC Committee
  5. M0LEP

    M0LEP New Member

    Looking forward to seeing those.
  6. M0JAV

    M0JAV Moderator

    Last edited: Oct 24, 2018
  7. G3YMC

    G3YMC Member

    Thanks for that. I will read it when I have some time.
    I attended the presentation at the convention on Saturday. Like others I found that dwelt far too much on the technical details, in particular an unnecessary long description of FFT and other aspects of VDSL2 whereas in the short time available it might have been better to concentrate on what progress has been made with Ofcom discussions and practical tips for those affected. Lelantos is an interesting tool but the details are not really of interest to us end sufferers.

    I recently upgraded to VDSL here, all cabling underground and 800m or so from the cabinet. I am pleased to say that I have no detectable interference from it at all and cannot see any of the transition gaps. 40Mbs stable connection. You probably already know why some suffer whereas others do not and maybe it is the reasons for this that need more investigation and discussion with Ofcom and Openreach.
  8. M0JAV

    M0JAV Moderator

    Thanks for your comments. I am pleased you do not have problems with your installation as you said
    "I recently upgraded to VDSL here, all cabling underground and 800m or so from the cabinet. I am pleased to say that I have no detectable interference from it at all and cannot see any of the transition gaps. 40Mbs stable connection. You probably already know why some suffer whereas others do not and maybe it is the reasons for this that need more investigation and discussion with Ofcom and Openreach"

    One thing that is always necessary is some conductors acting as a resonant antenna connected to the VDSL modem. This is usually either the incoming telephone line or the in house extension wiring. Whatever acts as the VDSL RFI antenna it has to couple into to the amateur receivers. So with underground cabling and no extension wiring causing problems you appear to be one of the lucky ones (real problems occur in about 25% of installations, from our survey results)

    If the problems are low level they can be alleviated by moving or changing the type of receive antenna to reduce coupling from VDSL source.

    As you probably know a neighbour changing his broadband to VDSL may give you problems at a later date as in the vast majority of cases we have investigated the problem is a neighbours service not the amateurs own.

    Anyone who has SkyQ has another antenna the mains wiring connected for PLT in home distribution via mains. The connection to mains to act as an antenna will be there even if the PLT is not in use.

    Thanks also for your earlier comments on this thread
    John Rogers M0JAV
  9. G3YMC

    G3YMC Member

    The broadband is actually fed from an extension here as the master socket is by the front door with no power sockets. But it is a single short hard wired extension to the upstairs shack and the master socket is one of the ones with a built in filter on the ring wire - not the latest, a few years old (I know I could disconnect the ring wire if needed). As far as I can see this is totally balanced. You are right that many problems are due to extensions and the ring wire may be the prime issue.
    73 Dave G3YMC
  10. Ken G3SDW

    Ken G3SDW Moderator

    I totally agree with the previous post, far to technical for most members but very clever indeed.

    For me then i have two questions, as no doubt many others will have the same, 1. Once a member has proved that he has a VDSL problem, then 2. how will this system locate it and more to the point 3. Will it eliminate it, the answer in both cases must be no.

    When members come to me they ask three questions, 1. What is it, 2. Were is it and 3. how can we fix it.

    The first one we can answer, the other two we cannot, locating it will be just back to leg work and a portable, the next one will be down to BT/Openreach, there you have the stumbling block.

    So although we can prove what it is then that will not satisfy a member as they just want it fixed.

    These are my personal thoughts looking at it from a member`s point of view.
  11. M0JAV

    M0JAV Moderator

    Ken asked

    "Once a member has proved that he has a VDSL problem, then 2. how will this system locate it and more to the point 3. Will it eliminate it, the answer in both cases must be no."

    The RFI (white noise level) from VDSL comes from multiple sources and cannot be reliably located with a traditional receiver, even looking at VDSL band transitions gives unreliable results because of the multiple sources of RFI from each nearby subscriber and other sources like SMPSU's all adding up. The package described identifies the VDSL signature and measures its level, so it can help to find the biggest source of problem if recordings are taken under each drop wire or near each house then they can be analysed to find the major source of problem.
    As far as alleviating or eliminating the interference with modern dual receiver SDR's and this signature analysis we are trying to develop software to cancel VDSL noise. So Ken the whole purpose of this work is to be able to answer yes to both of the questions you pose.

    Unfortunately whether it will have any impact on Ofcom's attitude remains to be seen. Without Ofcom's support getting further action from Openreach is unlikely.

    John Rogers
    EMC Committee RSGB
  12. Ken G3SDW

    Ken G3SDW Moderator

    The most important part of you post John is the last paragraph.

    So even if you can locate it, then as you say it is most unlikely that BT/Openreach, even if they confirm that the location is correct, then the member will still have the problem, as so far they do not have the powers to instruct the owner to rectify the problem, which ever that way is.

    Its so sad that we cannot work along side BT/Openreach for the same goals.
  13. g0tvm

    g0tvm New Member

    Hi All

    Since last Thursday 15 Oct 2018, I have become a victim of the ADSL, before the 15th Oct I had no issues with VDSL whatsoever, however it has now appeared on my 80m band and site from 3.752Mhz all the way up to 5.2Mhz, the noise level below 3.752Mhz is S7 however any thing above this frequency has risen to 9+10dB, This of course now means I cannot use any frequency above 3.752Khz or take part on the WAB net 3.760Mhz.

    The noise is pretty much permanent but does have the tendency to disappear for short periods of time. Also if I use RTTY on any frequency from 3.752 MHz the VDSL signal disappears and will eventually restart restarts.

    I have located the two poles outside my house as the source of the noise as an AM receiver will go wild when I am underneath the poles.

    Recently one of the property next door to me has been vacated and some new neighbours have moved in, I wonder if either the previous owners had VDSL and have now disconnected thereby having an terminated point, or the new neighbours have had BT broadband installed.

    So to recap:
    1. Before the 15 Oct I had no issues,
    2. Below 3.752Mhz, my noise floor is S7, above 3.752 the noise floor is S9 + 10dB when the VDSL signal is there.

    Also there is the secondary VDSL carrier on 8.56 and ends around 9.6, this is part of the same source of interference, i.e. when the 3.752Mhz carrier disappears so does this 8.56Mhz.

    Question now is how do I contact BT Openreach to get them to sort this out.

    I have uploaded two videos on YouTube if you are interested in viewing them, they can be found here:


  14. Ken G3SDW

    Ken G3SDW Moderator

    The noise is pretty much permanent but does have the tendency to disappear for short periods of time.

    Abdul can you expand a bit more on this comment as VDSL is normally there 24/7.
  15. Ken G3SDW

    Ken G3SDW Moderator

    One other comment Abdul is that you cannot contact Openreach/BT as they do not take calls such as this we provide a contact system but will come to that later.
  16. g0tvm

    g0tvm New Member

    Hi Ken

    The carriers is mainly there however for sort period of time and pretty much random the carrier disappears and I no longer get any interference but this is short lived as it restarts it self a few moments later, I believe the VDSL carrier is retraining it self as its probably getting some interference from somewhere, (you can see the carrier startup on the first video where the VDSL carrier dropped for a short time and restarted) sometimes it will be there for 30mins then stop for a minute or so and restart. However yesterday I saw a BT openreach engineer playing in the cabinet down the street and when I came back holding my breath sadly the VDSL carrier was still there, however around 17:00 yesterday the carrier was no longer there, I kept checking my radio on and off up until 22:30 and the VDSL carrier was not there at all (allowing me to sleep really well with the knowledge it was sorted), but this morning it was back up again making it difficult to have a qso on the barometric net 3.775Mhz.

    As I said above by sending out an RTTY signal it seems to clear the carrier for a short period of time anything up to a minute or so then its back.

    I hope this answers the question.

  17. Ken G3SDW

    Ken G3SDW Moderator

    Well yes it does to a degree, you use the word carrier but seeing your clips then that is just noise which assume is broadband

    The easiest way to check for retraining then listen on 10.104Mhz if the carrier, unmodulated, then transmit for a couple of seconds and tell me what happens.

    From all you comments then i do think that your new neighbour is were it is being generated, but if he has the correct face plate and does not have lots of extensions then in most case there is not a problem with VDSL.

    If it is your neighbour causing this problem you will at some point have to talk with them, but my advice is to go lightly and do not accuse then in any way at all just ask for there help, you need them on your side.

    If you don`t then they could well shut there door and refuse to help and there is no one that can force them to cooperate, not even Ofcom
  18. g0tvm

    g0tvm New Member

    Hi Ken

    This is probably teaching granny to suck eggs and I apologise in advance, I use the word carrier as the signal appearing on my radio has a start frequency 3.752Mhz and an end frequency 5.2Mhz, therefore a broad carrier with a bandwidth of 1.45Mhz. If you look at any digital signal on a spectrum scope it has a start point and an end point, to our radio this appears as an elevated noise within its space, but to a proper decoder the info can be decoded. In the case of VDSL BT have used the frequencies that don't belong to them and as such their carriers have appeared on the amateur band and has caused the noise floor to be elevated, in my case by at least 15dB on 80m.

    I did this and nothing happened.

    however about 10 minutes later the broad carrier (i.e. the one that is causing the interference on my 80m disappeared for a shot period, when it started to come up again, there was lots of little narrow band carriers on the 10Mhz band, once the broad carrier on 3.752 came up, all the narrow carriers disappeared and the 10Mhz band was clean again.

    Regarding the neighbour, I will keep him on my side and have no intention of accusing them of anything. first step is to find out if he is using BT broadband. If not maybe the line is unterminated and has started to radiate, all speculations at the moment.

  19. Ken G3SDW

    Ken G3SDW Moderator

    Well it does seem to be retraining and someone has had a new installation of Super fast Broadband and the most likely candidate is your new neighbour.

    Have you got over head phone lines or underground?

    i think sooner than later you need to knock on there door to at least eliminate them if need be.

    Then i suggest that you contact our John Rogers M0JAV m0jav@rsgb.org.uk to ask him to get a line balance check at your location, he is the only guy who has access to to Openreach/BT

    Let me know what happens.
  20. g0tvm

    g0tvm New Member

    Hi Ken

    Will do.

    I just had a long chat with two random BT openreach engineers who were working a few blocks away, they were very helpful, I told them of the issue and showed them the video, they agree its a VDSL signal and could be possibly mis-terminated or a faulty router/modem or possibly some equipment that the neighbour has connected. They said its usually other way around they have to put filters on the customers equipment if they suffer interference.

    They took my mobile number and said they will drive pass and take a look at the number on the pole and see what they can find. I'll keep you informed if they get back to me (or I get a brick tru the window).


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