Twisted pair reduces noise pickup, it does not eliminate it. Even with twisted pair cable, a 100m run above ground which is not inside a shield will pick up noise.

If you can get a clear line of sight with outdoor ariels, wireless would seem to solve the afore mentioned problems, and 100m shouldnt be a problem

Do you mean radio noise? Well, the main run from the exchange will not be screened either will it unless it's all underground?

Noise from adjacent pairs?
Noise induced will be proportional to length - high with main feed, low with his extension.

Still worth a try.

Phil B

In reply to:

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Do you mean radio noise? Well, the main run from the exchange will not be screened either will it unless it's all underground?

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Most of the wiring from the exchange will be underground, apart from runs of about 100yds from poles in the road, which are usually steel reinforced, and therefore quite well screened. The noise picked up is mainly MW radio, which shares the same frequencies as ADSL.

Noise from adjacent pairs is less of a problem, generally.

Hmmm, I was trained by the Post office in 1971 ....

Running cables between adjacent and nearby properties has not been illegal since Post Office Telephones was prepared for privatisation.

BT cables my or may not be screened, some are still lead sheathed, some are not. External cables using aluminium conductors was grease filled to prevent oxidation. The maximum cable length from an exchange was set at 3 miles. As distance from the exchange increased, so did the diameter of the conductors. Beyond 3 miles, it still worked, but problems started to arise. The real problem was loop disconnect dialing and not, as many appear to think, speech. (Speech is degraded in the phone itself by far more than the line would do it). A 10 pulse per second was almost invisible at the exchange due to inductance in relay circuits and the lowered current due to line resistance. DTMF will not suffer the same degradation so shoudl operate over longer distances.

Bells would also be affected. The maximum number of bells was limited to 6. This was quite optimistic, as I once installed a Housemaster with 10 stations, and the bells were suffering after the 4th was switched on. (Hence REN numbers).

100 metres is the maximum length that can be used for an ethernet segment. This effectively eliminates ethernet as an option. Yes, it might work, but the error rate will be high.

The pairs in a cable are twisted to prevent cross talk within the cable. With a cable length of 100 metres this is unlikely to be an issue.


Assuming your neighbours are quite happy for you to lay cable across their property and you can conceal it sufficiently to prevent eavesdropping, then I do not believe that you would have a problem extending your line and using ADSL at the extended end. I would suggest that you look for thicker cable, and use that. Maplins are a good choice for cable, but if you cant get it, then standard 0.5mm will do. Keep it as a single length, so buy the whole reel. Whatever it costs will be less than transferring a service and transferring it back.

Ordinary cable will last in high wear situations for up to 12 months. (This was in a pub, with people walking on it).

Make sure that you use the pairs in the cable, so pull the sheath off carefully and you will see them loosely wrapped together. Keep it away from mains. (The maximum permitted length adjacent to a mains supply was 6').

SJB99. My point was about Wayleaves. It is not legal to run cables across other people's property (even for BT) without permission - a Wayleave.

Edited by Beerhunter (Thu 02-Aug-07 10:06:41)