VDSL Emission Investigation

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

  1. G4LNA

    G4LNA Member

    Already asked him that, no extensions, the router plugged directly into the master socket and one phone plugged into the filter, all as it should be.
  2. Ken G3SDW

    Ken G3SDW Moderator

    Brilliant Paul, thats one hurdle out of the way.
    73
    Ken G3SDW
  3. Ken G3SDW

    Ken G3SDW Moderator

  4. G4LNA

    G4LNA Member

    I have some more news, but hold on and I'll relay what is exactly happening later.
  5. G4LNA

    G4LNA Member

    The update as promised.

    My neighbour called EE and they tested the line and confirmed there was indeed a major problem, so they got my neighbour to carry out what they call a hard reboot which restored his internet, but they still called Openreach just to be sure there were no other underlying problems. Within a few minutes of EE reporting it an engineer called my neighbour as said he would be around straight away as he was in the area. The Openreach engineer was there for over an hour carrying out checks.
    I haven't spoken to my neighbour yet, but I will do sometime just to ask if the engineer found anything. But that was quick service I must say. Luckily my neighbour is also an engineer and I showed him the videos and explained VDSL to him and the problems it can cause, so being an engineer he immediately understood.

    All this time I have been listening to 30M and the noise I was getting has gone and can hear stations again.
  6. Ken G3SDW

    Ken G3SDW Moderator

    Well thats is very satisfying news Paul which i know the rest of the EMCC will be very pleased to hear so i am now going to pass this info on to them.

    Alls well that ends well.

    73

    Ken G3SDW
    Last edited: Mar 18, 2017
  7. G4LNA

    G4LNA Member

    Just to let you know Ken that I'm going to contact John yet again, the noise greatly reduced on 30M it now 24db above what it used to be, so it hasn't been completely fixed because of this raised noise level. Sorry mess everyone around, but it's the first time I've had a chance to check it out properly.
  8. Ken G3SDW

    Ken G3SDW Moderator

    OK Paul, i have informed the EMCC about yesterday`s actions from Openreach which proves one thing and that it can be done if all parties go that extra mile.

    73

    Ken G3SDW
  9. G4LNA

    G4LNA Member

    Thanks Ken,

    Well, further development. I didn't bother checking the band after my last post, because I was on top band after that. This morning when I checked there is no noise whatsoever on 30M, I thought the aerial had fallen down, I can't even hear the carriers like I used to. I'm wondering if the Openreach engineer went elsewhere after leaving my neighbour, maybe did something at the cabinet? I don't know, suffice to say that the noise level is around S1-2 instead of S6 yesterday.

    I have let John know by email, just out of politeness.
  10. Ken G3SDW

    Ken G3SDW Moderator

    There is a good possibility that he did Paul, let us hope so.

    All you can do now is keep an eye on things, lets hope that things remain as they are now, it is a very good sign that the carriers cannot now be heard.

    Update us here if there is any change.

    73

    Ken
    G3SDW
  11. M0HUX

    M0HUX New Member

    Glad you're getting somewhere Paul. I tried to attach a video of the noise I'm getting to John, showing the radio running mains power, and also running from a battery with the mains switched off, and no difference. But the file exceeded 25mb so wouldn't send.
    I can try and add it here and see what you guys think ?. But I'm crap at that sort of stuff, so I hope I don't add footage of Dirty Gertie from number 30 by mistake ?. lol

    If that link works, then Gertie can be spared the blushes. lol
  12. M0HUX

    M0HUX New Member

    Cheers Ken. I'm beside myself now. It's soul destroying, having the equipment sat there gathering dust because I can't use it.
  13. M0HUX

    M0HUX New Member

    Thank you very much John. I wasn't being funny, just anxious to get something sorted, as you can imagine ?.
  14. M0JAV

    M0JAV Moderator

    What is the impact on VDSL etc of transmitting in cases where the interference is high, ie the coupling is high?
    I'm not suggesting we should be doing that deliberately but it is a fair point that if transmitting causes substantial problems then the customer has a legit reason for wanting the problem resolved. I'm asuming that if there is mutual interference then the amateur has priority, but has that been fully checked?
    73 Alan

    This is what happened when I transmitted 100W of CQs on 10MHz. The tones run away for a while, and I can knock a decent hole in there, but the noises come back 6/12s after I stop sending. The vertical lines are the 4kHz spaced training tones, not a grid on my display! http://www.g4dbn.uk/wp-content/uploads/2016/01/vdsl3-1.gif

    Video of the same effect here: http://www.g4dbn.uk/wp-content/uploads/2016/03/ELAD-FDM-SW2-Ver-1.120-16_03_2016-00_13_11.mp4

    Zero to 3s is the baseline hash level with no training tones. The silent bit from 3 to 10s is where I am transmitting.

    The slots +- 20kHz drop off from 11s, and raise the hugely loud trainnit tones. The hash starts coming back from 17s, leaving only the very close slots, which come back at 22s. the training tones stay around for at least ten minutes.

    I need to transmit for half a second every five seconds to keep the noises at bay, and that has allowed me to work a few stations on 30m when split, so long as they are not close to the 4kHz tones.

    I can't imagine that losing 40kHz of bandwidth is going to have much impact on a multi-megabit stream. I had an idea about using a separate low power transmitter sending my callsign 10kHz from my receive frequency into an antenna very close to the neighbours' dropwires to annoy their DSL enough to make it go into training, but it is all just too much like hard work. At least on VHF I can beam away from the horrible racket made by their LED lights, solar panels, PLTs electric fences and SMPS.

    Neil G4DBN


    How many 4 kHz carriers do you knock out when you transmit? I suspect about 20 which means your neighbour is unlikely to notice a reduction in bit rate on his VDSL service particularly as it is the upstream band that loses tones.
    If you do find out which line is being knocked out then the problem is likely to be pick up on the extension wiring in your neighbours house. You might like to think twice before trying to fix the neighbours line. If you are unable to cause the interruption at the frequency you want then the system will not retrain and you will loose the reduction in VDSL noise caused by the system not using tones near the frequency you transmit on. This will make it more difficult for you to receive the weak signals on 10MHz band.
    In simple terms when you transmit and the VDSL retrains then the white noise from VDSL disappears and you get background noise (which unfortunately still contains VDSL noise from other unaffected VDSL lines). Many amateurs find doing this allows them to use the 10MHz band.
    John M0JAV

    I will try to copy this thread onto the EMC matters forum so people who do not follow RSGBTech can see the exchanges.
  15. M0JAV

    M0JAV Moderator

    Ken G3SDW likes this.
  16. G4LNA

    G4LNA Member

    Mmm, call me Mr cynical, if I didn't know any better then I say there are some back-handers to get this swept under the carpet once and for all, why else are they trying to cover it up with gobbledygook.
  17. M0AFJ Tim

    M0AFJ Tim New Member

    Can I ask M0JAV if a detailed technical response to this OFCOM report has been sent?. If you need a site to take some measurements as to the destructive effects of VDSL I can make my QTH available in Milton Keynes at any time.
    Has anyone from the RSGB discussed this with Peter, G3RZP?.
  18. M0AFJ Tim

    M0AFJ Tim New Member

    Don't be defensive Ken, I was not implying criticism. Peter has been making some very good points on the CDXC web site, as you may know he spent many years on the various EMC standards committees, I just thought it might be useful to talk to him, my apologies.
    My offer of my site still stands if it's of use
  19. Ken G3SDW

    Ken G3SDW Moderator

    Not being defensive at all Tim but it came across as you did not think we had sufficient guys on the EMCC with the ability to involve ourselves with this subject ie VDSL.

    Quite the opposite in fact, watch this space
  20. M0AFJ Tim

    M0AFJ Tim New Member

    My apologies again, it was not my intention to question the abilities of the EMCC.

    I'm out of here
    73

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