Telephone or CAT cable for ADSL

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There are frequent conversations about whether using CAT5 or CAT6 data cable for ADSL signals degrades the ADSL signal more than it would be if CW1308 was used.

It seems there is no fit all answer.

An aquaintance of mine was involved with the design of test and measurement equipment during the evaluation and development of the ADSL signalling format. His remit was to provide means to inspect and record the waveform of the ADSL signal at various points along a ciruit route without the test probes affecting the signal. Other people took the waveform data to analyse it.

Some routes were actual exchange to customer pairs through the network and others were simulated in the laboratory or were test cables laid out around the site.

Simulated lines designed for telephony up to 20 kHz ( resistors, capacitors and inductors in a box on the bench ) failed to simulate a line when ADSL was sent through them.

The recovered waveforms from points along the circuit were compared with the waveform injected at the start of the circuit. Both ADSL signal and the data produced from the ADSL signal were recorded.

Replacing a length of cable with a different type of cable did affect the ADSL waveform. In some circumstances there would be an improvement in the "quality" of the ADSL signal while in others the quality would be reduced. The length of the section replaced had a bearing on whether the signal quality was improved or degraded.

A few feet of jumper cable in a street cabinet was seen to have a noticable effect ( visible on the oscilloscope ) on the ADSL signal. The effect was noticable different depending on whether the jumper pair was normal twist, un twisted or over twisted.

CAT5 and CAT6 have very high twist rates. The observations in the street cabinet suggests a short length of cable that has a different twist rate to the rest of the cable route will affect the ADSL waveform. Whether this effect degrades or improves the ADSL signal and / or data rate was not available to my contact.


It was too much to take when a circuit with an open leg still carried ADSL to the customer in a format that the modem could convert to data

I conclude that using CAT5 or CAT6 between the NTE 5 and the modem / router may or may not affect the data quality.

From another engineer "" Because the DSLAM adjusts the data rate and ADSL signal to compensate for the line quality there is the possibility that a length of mis-matched cable at the end of the line will influence the operation of the DSLAM such that the data is not affected or possibly improved ""

As I said it is a black art more than a science to get 20Meg of data through a network designed originally for a maximum of 3kHz audio.
 
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Telephone cable for ADSL/VDSL. Because its "tuned" to be best through a low twist rate copper pair.
Even VDSL using frequencies up to 17MHz ish..

Once it goes through the router, the frequencies used are much higher, so cat 5/6 is used.
 
Telephone cable for ADSL/VDSL. Because its "tuned" to be best through a low twist rate copper pair.
Even VDSL using frequencies up to 17MHz ish..
BT don't agree with that statement.
 
BT are a service provider. A salesman if you like.
Altering the characteristics of a copper pair anywhere between the DSLAM and the router/modem will always have a negative effect on the pair. Having aluminium joined onto copper will have a negative effect. As will changing from a few KM of telephone twisted pair onto cat5/6 for the final 30 or so meters.
I have experienced this in new build properties wired in cat5. The Dynamic Line Management may set a slower speed because of the inconsistancy of the pair. It will affect the AC Balance.
 
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Why would BT use a higher (more expensive) spec cable than required?! The EU 99% of the time knows nothing about cable nor cares, they couldn't care less if it's angel pubes coated in gold supplying their line or CCA junk so not sure why you think BT are trying to sell something!! (CCA is a COMPLETELY different scenario btw). I guess BT agree as they use a CAT5 spec 2 pair cable now.
 
[Why would BT use a higher (more expensive) spec cable than required?!
Why carry two reels of different cable when one will do two jobs with no way the EU ( end user ) can detect or measure the advers result that result.

The EU 99% of the time knows nothing about cable nor cares, they couldn't care less if it's angel pubes coated in gold supplying their line or CCA junk so not sure why you think BT are trying to sell something!!
BT ( Openreach to be accurate ) technicians are not trying to sell anything, they just want to turn the job round in the shortest possible time qith the least amount of effort.

The last three domestic installs I have seen have been CW1308 from the internal block at the end of the drop wire to the NTE5

(CCA is a COMPLETELY different scenario btw). I guess BT agree as they use a CAT5 spec 2 pair cable now.
CCA = ?
 
It's nothing to do with carrying two reels of cable & it wasn't me that suggested BT are trying to sell something. You may just have to admit it, using CAT5 cable has no ill effect on ADSL or vDSL. If you don't know what CCA or CCS is you need to do some more homework. ps, the cable is from BT Cables Ltd NOT BT Openreach to be accurate :)
 
BTW, the original post mentioned jumper wire, BT have a xDSL 30Mhz jumper wire available now too...
 
They may have it, but in the real world nobody uses it.
And most Openreach engineers, as Bernard said, just go to the stores and pick up 2/4/8 pair internal, they dont care about the spec, more what they find easier to work with.
BTW, BT insist on using CAT5 to run data extension ports from the SSFP to your router, I'm really not sure why? Maybe due to electrical interferance within the property?

A single run of CW1308 shouldcarry ADSL/VDSL better than the same distance of half cat5 and half CW1308. A single run of cat5 will not outperform CW1308 unless in a really noisy environment.

The pairs in 50 meters of CW1308 are also shorter (thus have less loop resistance) than 50 meters of telephone cable due to the lower twist rate.
 
Sorry but that goes against what we & many find. Indeed over the CAT5e horizontal length limit there is normally no drop off. BT stipulate their CW1724 cable for that very reason between the vDSL plate & the modem. CW1308 is no easier to work with than CW1724 btw, that's why they bought it out ;) It's CAT5 spec BUT only 2 pair & also available in external grade.
 

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