Member Avatar for CarolClark

If I run a 100 foot phone wire around the house to install another jack, will that lower my DSL speed.Is there a maximum length for phone wire, before it lowers the signal?

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Short answer: a 100 ft run of proper twisted‑pair phone cable inside your house will not meaningfully slow DSL by itself. The big limiter is the long copper “loop” back to your provider. For context, Category‑3/5e twisted pair loses roughly 2.0–2.6 dB per 100 m at ~1 MHz. Your 100 ft (≈30 m) adds only about 0.6–0.8 dB of loss, which is usually a small change in the modem’s noise margin. Problems arise when the run is untwisted “quad”/flat satin cord, daisy‑chained jacks (bridged taps), or parallel runs next to power cables. Use a single dedicated twisted pair and avoid flat cords. (solutions.borderstates.com)

Good troubleshooting flow (building on ’s SNR advice): first, read your modem’s stats for SNR/Noise Margin and Line Attenuation. Then plug the modem into the test jack in the NID/demarc outside to see what the line looks like before your inside wiring. If the SNR/attenuation is clearly better at the NID, the inside run or jack wiring is the culprit; fix with a clean homerun. (draytek.co.uk)

Best practices for your new jack:

  • Run one homerun of Cat5e/Cat3 from the NID to the DSL jack; avoid splices and daisy‑chains. If you have voice on the same line, install a central POTS/DSL splitter at the NID, or put microfilters on every voice device. (cablinginstall.com)
  • Keep DSL leads short and away from AC cabling; if you need distance, put the modem by the jack and extend from the modem using Ethernet. The familiar 100 m (≈328 ft) limit people cite (as did) is for Ethernet, not DSL. (en.wikipedia.org)

Finally, ignore the idea that “DSL speed is not dependent on wire length” (). Your sync rate tracks line attenuation and noise margin, both of which worsen with added length or poor wiring. (draytek.co.uk)

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All 8 Replies

Member Avatar for Techi

Did u mean ADSL? Yes the length of wire does matter because also anything could happen in between (a few users had their dogs chewed the wires, i'm not joking).

Having said that, every case is different. I think u should deal with the problem IF it comes. There could be other reasons for slow connections.

Member Avatar for sparkax

The maximum is 100 metres. Approx 300-ft.

Member Avatar for vaniliao

You can not use a telephone cable as short as wall outlets are located in places near sources of heat, angles, etc. and look at our house you can not set the computer near wall outlets. In addition, we would have wires all over the place, making great opportunities to travel and get hurt, or put together tables.

Member Avatar for techsheaven

Phone wires travel from the Central Office, to (and through) your home as a twisted pair. The pair of wires is twisted to cancel cross-talk (foreign noise induced on the pair). The quality of your connection is dependent on a SNR(signal-to-noise ratio). Using a long line-cord is not the best idea, but if you have no issues, give it a try. I would get a baseline SNR near the jack, and compare it to the SNR on the long line-cord. It would be in the modem transciever statisitcs under SNR, or Noise Margin. Make sure you are comparing apples for apples though... make sure your downstream and upstream data rateson the second test match the rates on the second!

Member Avatar for sebastianedu

DSL speed is not depand on wire length , speed slow downd when number of user used dsl Connection .

Member Avatar for paul_999

should not affect the speed really over 300ft could see a small drop in speed but hardly noticable

Member Avatar for techsheaven

When we talk about length limits for DSL, there is the twisted pair from the Central Office to the modem, and the two or more twisted pairs from the modem to the PC. 25000ft is the untreated theoretical length limit to the modem. The 300ft limit would be for Ethernet.

Member Avatar for PcTestCard.com

I beleived there will be a very small effect on the speed.

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