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ADSL: too far from the CO? Use a second pair?

Discussion in 'Electronic Basics' started by Dan Jacobson, Sep 6, 2005.

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  1. Dan Jacobson

    Dan Jacobson Guest

    Say if we need a thicker cable to transmit signals better,
    then one could just add additional strands no?
    And what if these strands just happened to come with insulation?
    Anyway, am I not just still increasing the surface area along which
    the signals flow? And what if these strands just happened to be two
    pairs out of a bundle of 100, etc.

    But in comp.dcom.xdsl 31 Aug 2005
    Re: too far from the CO? Use a second pair
    they tell me 9 women can't make a baby in 1 month etc. Sniff.

  2. You need what is called "Pair gain" to extend the distance. Make
    sure that not only are you sitting down, but have your seat belt on when
    you ask what it will cost.
  3. Don Bruder

    Don Bruder Guest

    Hell, The folks three miles further up the road from me are ALL on
    pair-gain equipment. Which, I'm told by the phone guys who have shown up
    at my place to fix problems, is the reason that they count themselves
    lucky to get a 2400 (yes - two, four, zero, zero) bps connection when
    they try to dial into an ISP.
  4. Don Bowey

    Don Bowey Guest

    Are you sure there is a mux that can transport ADSL. Which IS just a twisted
    pair technology?

  5. Don Bowey

    Don Bowey Guest

    If 2400 is the best they can do, they have the sync screwed-up - classic.

  6. J Shrum

    J Shrum Guest

    I think you should have specified DPG (digital pair gain)... And if telco
    doesn't have it on the drawing board, then it doesn't matter how much one
    was to beg... it aint gonna happen.
  7. Terry

    Terry Guest

    "Pair gain" may mean different things to different folks. For example audio
    gain amplifiers and/or inductive 'loading' coils, typically 88 millihenry
    added at distances of, IIRC, each 6000 feet to improve voice pair losses, on
    very long telephone loops. That treatment works up to an analog frequency of
    around 3500 hertz! Loading, while reducing the lower frequency loss, in
    particular, 'cuts off' higher frequencies due to the added inductance,
    limiting bandwidth.
    A company I worked for did various pair gain work when a local US military
    base closed down. It's USAF private branch exchange was taken out of
    service. Following that subscribers in the base area, wanting telephone
    service were connected on very, very long loops to the private telephone
    company serving the civilian community some distance away.
    To improve telephone voice transmission various audio gain devices were
    added; even so the loops had very high resistance, which could affect
    signalling/dialling, especially back in the old rotary dial days!
    We don't get much really hot weather here; but on one or two exceptional
    days the resistance of some copper wires, inside the overhead black jacketed
    cables increased to the extent that telephone dialling failed; just couldn't
    get dial tone. At night things cooled down and telephones worked again!
    However 'pair gain' can also mean adding devices such as a 'subscriber line
    carrier'; this is often a transistorized device which mounted at the telco
    main frame and out on pole or in someone's house etc.. uses low frequency
    'carrier' signals over existing cable pairs which are already in use. This
    is done to avoid, say, installing any more cable on existing fully loaded
    pole structure or in already full underground conduits! In other words this
    'gains (the equivalent of) more pairs'!
    I seem to recall that such devices could be installed quickly for about
    $125; heck of a lot cheaper and quicker than running, say 5 miles of cable.
    So, for example, YOUR main phone might be on a cable pair; but that pair
    may also be used via one of those devices to provide telephone service, just
    POTS (Plain Old Telephone Service) to Mrs Smith two doors down. Naturally
    while the telco has met its obligation to provide telephone service such
    methods mean very poor bandwidth, both on the pair itself and the added
    service. Conditions which tend to require the use of pair gain devices tend
    to be farthest out from telephone company switching exchanges or 'wire
    centres' and/or are 'pockets' of residential development!
    Our telco here will not provide DSL service beyond certain defined limits;
    they will however do a test if the area is considered marginal or the
    customer insists.
    Our DSL comes about one kilometre over the same pair as our standard home
    telephone. As mentioned if the telco has to special conditioning, amplifiers
    rearranging of pairs in order to get DSL to work, it can get expensive. I
    have acquaintances who live just too far out in the country, as it were, to
    get DSL for the foreseeable future.
  8. Don Bowey

    Don Bowey Guest

    Everyone who reads this should do so carefully. It lacks..... Well that
    sums it up.
  9. Jasen Betts

    Jasen Betts Guest

    it depends what the problem is.
    probably not a bad thing
    yeah, by addiing an extra pair you decrease the resistance (and thefore the
    thermal noise) but it may not reduce all noise effects,
    The DSL equipemnt is tuned to the impedance of a standard copper
    pair, if you parallel a second pair the impedance changes and it stops

    You'd need some sort of matching transformer at both ends or possibly need
    to redesign the outpuut circuitry of the DSL units, I don't know of
    any place you can get that sort of stuff off the shelf.
    yeah it's a bit likee that.
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