Re: Cable

["Alan Ainslie" <alan.ainslie@xxxxxxxxxxx>]

Cheap CAT5 is a problem in many respects I am afraid.  It often will not
support network speeds due to erratic impedance etc even when properly
terminated and left in a coil.  You need to use a high-end Fluke or Wavetek
analyser to see this but it is amazing that the stuff ever gets to market:
the distributors clearly do not ever make any QA checks.

When you put the cable into a real situation with bends etc problem is
worse: think about 4 twisted pairs going round a bend, you can visual ise
either unwinding or tightening up of one or all of the twists if the pairs
are not securely supported: this is what gives impedance and crosstalk
issues along the cable length.

I assisted an installer recently who had a 5m run of CAT5.  Three pairs
were
electrically 5m: good news.  The fourth pair (and this was one of the data
pairs unfortunately) measured over 7m long electrically on the Wavetek -bad
news - and it did not work!

Very safe bet everytime is Belden.  And if you are able to justify over
£100a box (still only 35p a metre!!) then I strongly recommend the
'nanotwist' cables as being not only very high performance and they have
very low differential skew so ideal for KAT5 etc etc, BUT they have bonded
pairs which means that any cretin can take liberties with pulling the cable
and it still measures fine as the pairs cannot untwist on a bend.  So not
only works well, but physically easy to pull, and if it dies get snagged
the
performance holds up. Type number 7987R is typical of this class of cables
and is probably the one to specify.

PS  Simple but effective network tester available here if you don't fancy a
mortgage for a Wavetek.  (Also does the buzzer tracers that were posted
about recently)
http://www.the-max.co.uk/products/product_info.php?manufacturers_id=20&products_id=926&osCsid=2daa05b4f28dde5ed9ad6f2c1059daeeAlan
Ainslie----- Original Message -----From: "Chris Hunter"
<cjhunter@xxxxxxx>To: <ukha_d@xxxxxxx>Sent: Sunday, January 08,
2006 2:38 AMSubject: Re: [ukha_d] Cable> It was just that I'd assumed
I'd be going for the lowest price ... then> I saw the price range was
large, and the differences in attenuation were> huge ... 20db &
200db at 100MHz ... they'd not be selling the more> expensive types if
it didn't matter ... but which should I choose ? ...> and now the
snagging factor, too.>>