On 08 Nov 2011 17:32:33 GMT, Glen Walpert wrote:

On Mon, 07 Nov 2011 20:08:40 -0800, John Larkin wrote:

On Mon, 07 Nov 2011 19:37:53 -0800, josephkk
wrote:


Here is my first try:

That worked fine.

The page specifies a max prop delay of 555 ns, but doesn't specify the
length of the cable. Sounds like about 100 meters maybe.

The skew spec is awesome: 50 ns, or about 10% of the prop delay. That's
scary.

The method used to control crosstalk in UTP cables is to vary the twist
rate between pairs, so there is a pretty good difference in length of
wire between the pair with the slowest twist and the pair with the
fastest twist. IIRC the construction of Cat cables has both increased
the twist difference and tightened up the twist tolerance with every
increase in speed grade, to I would expect the skew in Cat 6a to be the
worst, but the most predictable.

Apparently you can buy two kinds of CAT6A cable, individually shielded
and not. I'd hope that the individually shielded stuff has the same
twist on all the pairs.

John