[RFI] Re-wiring station
jim at audiosystemsgroup.com
Sat Dec 31 03:55:24 EST 2016
On Fri,12/30/2016 8:50 PM, Robert Nobis wrote:
> As I recall, the CAT5 or CAT6 specifications do not actually specify that each pair have a different number of twists per inch. They do specify that all pairs be less than 38mm per twist and that pair twist lengths shall be chosen to ensure compliance with the transmission requirements of the standard. In practice, I believe manufacturers are using different twists per inch on the wire pairs in order to meet the specifications for cross-talk.
I haven't read the spec, but since crosstalk depends on the four pairs
having a different twist ratio, I would bet that those values ARE part
of the spec. I may be the guy who made hams aware of that practice. Some
of the big sound systems I was designing used Ethernet infrastructure to
carry dozens of channels of audio around facilities in sync with each
other, so I had to learn at least the basics of how those systems worked.
No, the original question wasn't about CAT5 cable, but the principles
are the same. I thought I answered the original question about twist
ratio -- more is better, but for our purposes to carry noisy power, it's
not critical. :) BTW -- twisted pair is also FAR superior to the
glorified zip cord sold to hi-futility nuts as speaker cable. I've
solved a lot of RFI issues by replacing zip cord with twisted pair, and
if big conductors are used (#10 - #12), the twisted pair also provides
the best possible audio performance from the speakers.
73, Jim K9YC
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