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The magic number for most DSL technology out there now is around 18000 feet. This is a function of the capability of copper to transmit high frequency over long distances. Past 18,000 feet, signal loss becomes increasingly unmanageable, bit errors rise fast, and therefore error-correction repetition of data means maximum reliable bandwidth is squeezed down to nothing. Thats the bad news.

The good news is that for the US, 18000 feet covers almost 80% of telephone subscribers (well, really, 80% of the US population). In addition, the phone company, in anticipation of the need for fast data rates and better quality lines, has been working on shrinking the average local loop lengths down in recent years, by installing smaller local hubs, known as DLCs or SLCs, that multiplex many lines onto optic fibre or other high quality lines that proceed on to the main switching centers. Most DLCs are not currently DSL capable, but the necessary hardware is out there, to upgrade them.

Many providers will not deal with you unless you are within 12000 feet.. this is to save the expensive of setting up a line to find that the quality precludes service, so being less than 18000 feet from your CO does not mean you can get DSL.

. When considering distance, the figures quoted by DSL equipment manufacturers assume good quality, thick, copper and under good conditions. For our area, even though our local loop is around 5000 feet, SDSL was limited to a maximum speed of 716k, half its theoretical maximum, probably due to oxidation and interference. (also see.. technical hurdles).

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