More cat5 woes - CCA

"Mike B"

** The ratio of resistance for copper and aluminium of equal cross section is 1:1.58

Just how are you measuring the resistance ?

.... Phil

Two different multimeters give the same results.

I have two cables running in the same conduit side by side for about 45m. One is AUSTEL approved, the other 'UL certified'. The only connections are to a solder tag patch panel (no punch down block) and a crocodile lead to do the loopback.

The AUSTEL approved cable gives 11 Ohm loopback for the green, orange, blue and brown pairs which sounds about right. The other cheaper 'UL certified cable' gives 25, 25, 68 and 68 Ohms.

Mike

"Mike B" "Phil Allison"

** Sorry, " multimeters " is not enough detail.

Digital multimeters are likely to mis-read badly ( usually waaay high) in the presence of contact resistance or AC hum. Try an old fashioned analogue meter.

If the numbers are not the same - be afraid.

Be very afraid.

Whatever the real problem - it is NOT due to the ratio of copper to aluminium.

.... Phil

:Whilst doing some dc loop resistance tests on some 'certified' cat5e cable I :found that green and orange pairs had 2x the expected resistance, and the blue :and brown pairs had 6x the expected resistance. :Close inspection revealed cooper clad aluminium with the copper thickness :varying depending on the pair.... : :Mike

What does "certified" mean and by whom was it certified? Did it have the A-tick symbol? What was the brand of cable which had copper-clad aluminium conductors?

Section 5.6.6.1 of this document

gives the Australian requirements for approved telecommunications cables. Other than coax, which is permitted to use a copper-clad aluminium centre conductor - provided the centre conductor is at least 2mm in diameter, all other cables must be either plain copper or plated (tin) copper. Table 3 gives the resistance requirements.

The label says 'NETCONNECT CAT5e CABLE E138034 1300 24AWG' which appears to be the UL number.

"Mike B"

** Have you seen this ?

.... Phil

:On Tue, 17 May 2011 10:10:23 +0800, Ross Herbert :wrote: : :>On Sun, 15 May 2011 14:18:56 +0800, Mike B wrote: :>

:>:Whilst doing some dc loop resistance tests on some 'certified' cat5e cable I :>:found that green and orange pairs had 2x the expected resistance, and the blue :>:and brown pairs had 6x the expected resistance. :>:Close inspection revealed cooper clad aluminium with the copper thickness :>:varying depending on the pair.... :>: :>:Mike :>

:>What does "certified" mean and by whom was it certified? Did it have the A-tick :>symbol? What was the brand of cable which had copper-clad aluminium conductors? :>

: :The label says 'NETCONNECT CAT5e CABLE E138034 1300 24AWG' which appears to be :the UL number.

That cable is definitely a Chinese knock-off and is not UL certified.

NETCONNECT is a proprietary trade name of AMP (Tyco). Here is the data sheet for their genuine Cat 5e cable. Note this is UL certified with the same number as on your Chinese cable.

If you believe

20% of the cable entering the UK is counterfeit.

Half way down the page it says, "Counterfeit cables can even have copper-coated steel or aluminium conductors in place of copper, ".

The resistance measurements of my cable would suggest that 2 of the 4 pairs are copper clad steel :-(

"Mike B"

** Is it obviously magnetic ??

Steel has about 7 times the resistance of copper.

..... Phil

The brown pair stick to a magnet :-( The green and orange pairs do not. I don't have any spare blue pair to test.

Well there you go. Fake UL certified cat5 copper/aluminium and copper/steel.

Mike

"Mike B"

** A cheap Chinese cat with no pedigree .....

Meeeoooooowwwwwwww.....

..... Phil

:On Wed, 18 May 2011 22:20:54 +1000, "Phil Allison" wrote: : :>

:>"Mike B" :>>

:>> If you believe :>>

:>> 20% of the cable entering the UK is counterfeit. :>>

:>> Half way down the page it says, "Counterfeit cables can even have :>> copper-coated :>> steel or aluminium conductors in place of copper, ". :>>

:>> The resistance measurements of my cable would suggest that 2 of the 4 :>> pairs are :>> copper clad steel :-( :>

:>

:>** Is it obviously magnetic ?? :>

:> Steel has about 7 times the resistance of copper. :>

: : :The brown pair stick to a magnet :-( :The green and orange pairs do not. :I don't have any spare blue pair to test. : :Well there you go. Fake UL certified cat5 copper/aluminium and copper/steel. : : :Mike

I see that in the USA they have instituted a laser holographic product labelling system for UL certified cable.

This might be of use to cabling contractors who buy bulk cable but for the hobby/small user who only buys a few metres off the roll at some unscrupulous or ignorant supplier, he could still get caught.

I have asked Communications Alliance

if they are aware of the problem and if there are plans to institute a similar labelling scheme here.

rote:

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belling

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lous or

The bad effect of this substandard cable over short runs in homes might be relatively insignificant compared to long runs, especially in noisy or such "unfriendly" environments, and/or in large commercial buildings where a signal might go through several very long runs of this crap cable to get from point A to B, and/or might have a substantial load on it from multiple users. - all these are unlikely situations for a hobbyist / home install.

I guess at the end of the day, you have to buy from reputable suppliers, and test it before installing it in a situation where it will be very difficult to replace it if there are found to be problems.

ey

belling

Will power over ethernet work when the resistance is 7x the expected?

Linksys are marketing their POE adaptor kit to home users

This one operates at 48v so it might still work.

depends on the distance and the required trigger voltage

yup I metered some clipsal titanium cat6 cable , 8.0 Ohms over 120 metres

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X-No-Archive: Yes

depends also on how much current the device being powered by it draws too.

:Whilst doing some dc loop resistance tests on some 'certified' cat5e cable I :found that green and orange pairs had 2x the expected resistance, and the blue :and brown pairs had 6x the expected resistance. :Close inspection revealed cooper clad aluminium with the copper thickness :varying depending on the pair.... : :Mike

Mike, can you tell me where you got this cable from?

email me direct if you would like to divulge this info.