11 km line, stable 512kb connection. 1Mb seem possible.

Discussion in 'Broadband' started by broughcut, May 30, 2005.

  1. broughcut

    broughcut Guest

    A good example of how a long line isolated from interference has very
    negligible effects on the availability of broadband.

    We are in the North York Moors national park, at LEAST 11km from the
    exchange; I think it is very likely to be in the region of 12-14km.
    There are about four street lights along the entire length of the line
    and no other obvious sources of interference, which is obviously
    significant.

    The 1 mile stretch of line to our house was installed about 10 years
    ago and the rest of the line is obviously rather ancient, so probably
    none of the thinner 0.5mm copper cable, which I think has been used in
    the recent past, and it is safe to assume no aluminum or steel cable
    either.

    Obviously, I got a "very unlikely" result for any and all ADSL
    services on the BT broadband checker on the basis of the length of the
    line.

    I ordered the day ADSL was installed at the exchange and the router
    synced (at 576000) on the fourth working day, three days ahead of the
    scheduled activation date. Few minutes after I tried to login for the
    first time the Plus Net account was automatically activated, as
    advertised. Superb service so far, certainly recommend them.

    Anyway, I'm running a Vigor 2600G connected direct to the main box
    via the ADSL faceplate from Clarity:

    SNR is typically 24.5 to 26, often holds steady at 25.

    Loop/line attenuation is typically 60. Sometimes it drops to 58.5,
    occasionally it peaks at 61. Never any worse than this, thankfully, so
    I think 1mb may be doable when/if BT upgrade the exchange, as it is
    mostly at or below the 60db BT limit.

    I don't think I have upstream figures on the Vigor but a totally
    stable connection and both upload and download speeds are superb.

    The minor fluctuations in signal/noise margin and attenuation may be
    due to local factors. We're not on the national grid so the router is
    currently powered by a generator during the evening and a DC-AC
    inverter (with a quasi-sine wave) the rest of the time (it's on the
    inverter now and reporting a very respectable 26 and 59 db so this may
    not have any effect). I intend to hook the router up to a car battery
    on permanent float, fused and converted down to 12v . The battery will
    produce a clean signal and it will be better to have the router
    connected 24/7.

    Hope this boosts the hopes of people in the sticks (who probably
    don't have to go to the expense of a Vigor afterall!).
     
    broughcut, May 30, 2005
    #1
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  2. broughcut

    broughcut Guest

    forgot to mention, I've been using the Vigor's long line firmware from
    the get-go. I may try it without and see if it has any noticable effect
    on the attenuation.
     
    broughcut, May 30, 2005
    #2
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  3. Attenuation is the level of loss of the original signal from the exchange
    to you. Changing the router firmware will not affect this (though it may
    measure it slightly differently). Nothing will improve or degrade.

    Whilst I am seriously struggling to believe you could be 14km from the
    exchange and getting a 60dB attenuation if correct, you should be able to
    receive 1Mb without any trouble. In fact, with SNR of 25dB you could get
    2Mb, though I suspect BT would just laugh at you if you asked.
     
    Simon Pleasants, May 30, 2005
    #3
  4. broughcut

    broughcut Guest

    My mistake. I think the extended line firmware makes allowances for
    poor attenuation. The line follows roads so I've taken a proper
    measurment on the map, some of my estimates were slightly off. It's
    10km by the most direct route, so I suppose it is unlikely to be
    longer than 11-12km. Still pretty good for 1 or 2mb.

    Is it usual for new exchange installations to be only 512K? I thought
    BT may just have throttled the line due to the long distance, but
    PlusNet are telling me I will have to wait for BT to upgrade the actual
    exchange before I could go to 1mb, but that I could call BT and ask
    them to turn up the gain on the line... I don't think gain has any
    bearing on the speed at which the modem syncs, so are they suggesting
    that this might improve the marginal attenuation and make an upgrade
    more likely?
     
    broughcut, May 30, 2005
    #4
  5. Better than pretty good - bloody remarkable more like. In my experience
    line distances are actually considerably longer than the crow flying
    distance. I am, for example, 1.6km from the exchange but my line
    attenuation indicates a line length of over 5km. But 12km does sound like
    something of a record to me. If your attenuation is only 60dB then it
    suggests a line length of only about half of what you estimate, though
    there are plenty of variables involved in that.
    Sounds like bollocks to me. There's no way BT would put ADSL equipment
    into an exchange which is only capable of 512kb. Almost every exchange is
    capable of 8Mb (there are a few exceptions).

    Turning up the gain on the line is unlikely to make much difference, I
    would have thought. Imagine listening to an old tape with lots of hiss.
    Turn up the music, the hiss gets proportionately louder as well. I can't
    see it making too much difference to the SNR which, ultimately, is what
    will affect the speed you can get.

    Could there be capacity issues at your exchange and what Plusnet are really
    saying is that BT have to upgrade *capacity* before they start speeding up
    any more users of the exchange? After all, virtual path congestion will be
    far more obvious to people on faster connections.
     
    Simon Pleasants, May 31, 2005
    #5
  6. broughcut

    broughcut Guest

    PlusNet tell me that the line was activated at the "maximum your line
    will support" but I've paid the upgrade fee this morning and they will
    therefore put a request into BT, but tell me not to expect anything
    since "it's already been activated at the maximum your line will
    support" ...

    I've asked PN to let BT know my SNR and attenuation results so they are
    in a better position to make this judgment. I think I'm right in saying
    noise margin can not be measured remotely and needs a user reading or
    an engineer visit, so it's largely supposition on BT's part? I mean,
    their website for this number still reports: "Our initial test
    indicates that it is VERY UNLIKELY you will be able to get Broadband
    from BT due to the very long length of your telephone line".

    The exchange is 5 miles as the crow flies, 7 miles by road -- and the
    line can only follow the road, there's no other place for it to go --
    assuming the line doesn't meander around other homes on its way here.
    We're a mile north of Rosedale on the Lastingham 01751 417XXX exchange.

    Last I checked, when they had that activation threshold thing going,
    only 130 people had even registered interest. The exchange doesn't
    serve a great deal of homes and since it was only activated on 18 May
    there are probably only a few of us on it at the moment. The online
    availability checker's low-balling doesn't exactly encourage
    subscriptions.
     
    broughcut, Jun 1, 2005
    #6
  7. broughcut

    kraftee Guest

    I think that BT (& Plusnet) are in a better position of knowing your line
    test results. Your router isn't calibrated & can be affected external
    sources of noise (not on the line)....

    BT (& PN) have got test facilities which will give them a more reliable set
    of results & the only way to get the deffinite results is to have a engineer
    call & run the APTS test from your end.

    The figures given out by your router are just guidelines. I've had 5
    routers here so far (had an ongoing problem which was always proved to be at
    this end, reboots, lockups etc), Netgear, Linksys, Draytek, 3 Com, & last
    but not least a Draytek. They all give different diagnostics, some even
    change if you change the firmware in the unit. If BT are stating that the
    line was activated at the max speed your line willl support the chances are
    you've just wasted some money..

    Having said all that, a little birdy has told me of changes in the near
    future (along the lines of RADSL) so be patient, you may be lucky.

    Knowing my luck I won't :-(
     
    kraftee, Jun 1, 2005
    #7
  8. broughcut

    broughcut Guest

    As fas as BT is concerned my line wouldn't support ADSL at all. They
    activated it for kicks as per their new try and see policy.
     
    broughcut, Jun 2, 2005
    #8
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