[RFI] Re-wiring station
k8ri at rogerhalstead.com
Sat Dec 31 21:16:57 EST 2016
I would add that in my experience THHN (house wire) used as twisted pair
has a "much" better memory than zip cord for twists. The BIG audio
cable with its very thick insulation make getting a reasonable twist
very difficult and much of that will untwist.
73, Roger (K8RI)
On 12/31/2016 3:55 AM, Jim Brown wrote:
> 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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