VDSL Routers

Discussion in 'EMC Matters' started by paulfw, Jun 10, 2015.

  1. paulfw

    paulfw New Member

    When a VDSL Router is upset by nearby transmissions I expect some of you know that they can
    generate one or more carriers close to the transmitted frequency, the carriers can last from a few
    seconds to several hours after the last transmission, this is called retraining.
    Does anyone know for sure what effects the owner of the router experiences ?
    I assume the internet service is interrupted briefly but maybe recovers quickly at a slightly reduced
    download speed which might go unnoticed.
    Is there someone out there who has their own VDSL router and can pass on their observations ?
    I do not own one and obviously don't wish to open a can of worms by asking local users.
    Beside being upset by my transmissions someone's router generates a wide comb of 4 khz spaced
    carriers, one day they covered 3.1 to 3.7 Mhz on another 5.4 to 6.9 Mhz maybe local noise is triggering
    this as on both occasions I had not transmitted for a long time.
    I can measure the frequency of these carriers very accurately so am almost certain the come from the
    same source.

    Paul G0HNW
  2. G3YRZ

    G3YRZ Member

    Hi Paul

    Nobody has come back to you yet, so maybe I can offer something useful although I do not have VDSL myself. I have ADSL broadband, best speed about 2.5Mbps, with a wireless network, and operate using only indoor aerials, a full size 80m dipole and a 20m folded dipole in the attic. Using these I cover all HF bands from 80m to 6m excluding 40m, on the odd multiple halfwave basis. Results are quite good, although that isn't the point of this note. There is a lot of RF around and I use a tuned counterpoise under carpets. My router is a Netgear DGN2200.

    My partner is very supportive where radio is concerned, but she does a lot online and the re-radiation and so on can knock out the router although only on 80m and 60m. No other bands are a problem. So the leads into and out of the router are pretty much encased in ferrite! This reduced the problem and short CW QSO's are pretty much OK on both those bands. Longer CW sessions and certainly SSB on 80 carries a high but intermittent risk of killing the internet. I think the intermittent nature arises from the actual ADSL signal received. I can have an SSB QSO one day but not on another.

    My experience as a broadband "user" may assist you. If I set up a download and monitor the Networking graph in Task Manager, I can see the impact of my RF on the download. Worst case, I can read the CW from the dips in the graph! My observations are that short interruptions, such as CW callsign once or twice and a 599 73 VA depress the download speed but do not kill the internet. Longer interruptions and SSB can cause temporary disconnection (the world disappears from the two monitors icon and is thus visible to a user) but the router reconnects quickly with no disruption from a user's viewpoint. Checking the figures, the reconnection is often slower and more resilient. A lot of SSB on 80 can cause a significant interruption which takes minutes to reconnect. Usually without speed loss once reconnected but very obvious to a user and even more obvious on Task Manager.

    I suspect anyone using the VDSL you believe you are affecting will have a similar experience to me.

    I hope this is some help and that a VDSL user will be able to add much more.

    73

    John G3YRZ
  3. M0JAV

    M0JAV Moderator

    When a VDSL Router is upset by nearby transmissions I expect some of you know that they can
    generate one or more carriers close to the transmitted frequency, the carriers can last from a few
    seconds to several hours after the last transmission, this is called retraining.
    Does anyone know for sure what effects the owner of the router experiences ?
    I assume the internet service is interrupted briefly but maybe recovers quickly at a slightly reduced
    download speed which might go unnoticed.
    Is there someone out there who has their own VDSL router and can pass on their observations ?
    I do not own one and obviously don't wish to open a can of worms by asking local users.
    Beside being upset by my transmissions someone's router generates a wide comb of 4 khz spaced
    carriers, one day they covered 3.1 to 3.7 Mhz on another 5.4 to 6.9 Mhz maybe local noise is triggering
    this as on both occasions I had not transmitted for a long time.
    I can measure the frequency of these carriers very accurately so am almost certain the come from the
    same source.

    Paul G0HNW[/quote]
    I have seen retraining only effect frequencies near the transmit frequency. To the VDSL user this would appear as a reduction in bandwidth and hence speed not a total loss of service. As most only use a fraction of bandwidth they would not notice. Indeed you can stop the VDSL using some frequencies for a time if it finds the frequency is not getting through. The wideband carriers are more likely to be caused by local sources near the router often conducted emissions stopping the router working properly. Only this week Ofcom have been publishing don't mount your VDSL router close to other electronic equipment. This problem is a lose lose game as the VDSL user is suffering and he is causing more interference. I had one report where the user had VDSL and PLT (both from the same supplier) and they interfered with each other so he could not watch his high speed video downstream.
    John Rogers M0JAV
  4. DrTeeth

    DrTeeth New Member

    My router (Asus N66U) is not affected at all by any of my transmissions even at full power (100W). Also, my antenna is so invisible, that even I cannot see it. Anybody experiencing any QRM would not know where to turn.
  5. paulfw

    paulfw New Member

    I have recently heard from a top band user who has VDSL.
    A brief transmission,even on QRP, made the download stutter and a more prolonged transmission made the modem reset it took about 2 mins
    to recover.
    By moving one leg of his dipole, something not everyone can do, and moving the router the problem was resolved.

    Paul G0HNW
  6. Ken G3SDW

    Ken G3SDW Moderator

    Thanks for that Paul, its nice to see someone who can think for them selves without just shouting "HELP", experimenting has always been at the heart of amateur radio.

    73
    Ken
    G3SDW

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