Hi All,
I could not resist adding my two cents worth. In the last
several years I spent at Bell Labs in NJ (moved to CA 4 1/2
years ago), part of my funding came from a group that was
responsible for UTP (Cat 5) and associated hardware. On
immunity performance, we were not able to find a shielded
system that would outperform UTP using the interface
circuits I had design input on. (When I first proposed the
circuitry, the group had an internal Bell Labs "balun"
expert review it. He did not understand how it worked.)
Emissions were lower compared to several shielded systems we
measured. The data was published at EMC Roma about 1995. If
I can dig it up, I will try to post it to my site later this
month.
Several formats of data were used including 100 Mb speeds.
We even did a demonstration of a 600 Mb over UTP cable
(section of the cable is within sight at this moment).
The conducted emissions on telecom leads spec was just being
written at that time. As I recall, we were pretty close to
meeting it except the method in the proposed standard was
not workable, so we used current probes and moving the
cables to maximize current (just like RE testing).
The net result is that UTP with the appropriate interface
circuits (not expensive, either) performs quite well
compared to STP systems. If anyone wants more into, email
directly to me and I will try and hook them up with someone
at Bell Labs in NJ who is currently on the project. It's
been a while and I am not sure what the present status of
that work is.
BTW, I recall that starting with a VERY well balanced
source/load, Cat5 cable inherently had about 12 dB better
balance, and therefore performance, than Cat3 for the high
frequency immunity/radiated measurements that I made. I did
not get much into the signal transmission differences
between Cat3 and Cat5 though.
Doug
Gary McInturff wrote:
>
>
> Another little nagging problem exists. Without going into the whole
> historically precedence UTP was a pretty important reason why ethernet was
> adopted so widely. The wiring was pretty much in place because of the cables
> that had been run for connecting office telephones etc. People don't want to
> drag in new cables (STP) because of the cost. I happen to agree with you
> assements below and wouldn't even consider UTP if it weren't for the
> existing installs and the 805 standard that (prefers?) it.
> Thanks
> Gary
>
> -----Original Message-----
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