Newsgroups: comp.dcom.cabling
Subject: Re: Patch Panel Termination
References: <[email protected]>     
Justin  writes:

> jon wrote:
> > Perkowski wrote:
> >
> >> Ya I know, but, Im talking about is 24 port patch panels...I never
> >> known installers to do that on panels like that.
> > But, as the pictures illustrate, so long as the twists are
> > maintained, the jacket, in this case not insulated should have
> > little effect being absent?
> 
> Yes, the missing jacket will defiantly have some kind of a effect on
> cable performance.  

The jacket is unshielded twisted pair wiring surrounding the wire pairs 
is mostly just a mechanical protection. The outer jacket protects 
the insulation of the individual pairs form mechanical damage 
that cna happen when pulling cable to it's place and when cable is 
is installed. The outer jacket also keeps the pairs mechanically 
ordered in the way they should (nicely evenly grouped together). 

The outer jacket has early no effect on the signal traveling on 
the cable! If you have just the original wire pairs from the 
cable, just as tightly together as they ar enormally on the cable, 
without the outer jackets, cable will perform still well for the 
signals traveling though it. No problems. It might be even hard 
to measure the difference between cable that has outer jacket 
or not.

When talking about single cable away from other cables, 
it should not matter much is the cable jacketed or not 
for the signals traveing through it! 
When you pack more cables together, the outer jackets 
keep some separation between the pairs form different cables, 
thus giving better isolation between the cables than just 
putting all the wire pairs from different cables tightly 
together. 
Other thing the jacket adds an extra electrical insulation 
layer. There is somewhat limited voltage that the cable 
can withstand between the wires on the pairs and between 
pairs. When the cable has this insulating outer jacket, 
the cable can withstand more voltage between individual 
pairs and outside of the cable than between the individual 
wires inside the cable. 

Things are somwehat different when talking about shielded 
cables (those that have braid/foil shield on the jacket). 
But for unshielded cables, the outer jacket is mainly just 
mechanical protection (agains mecanical damage and to 
keep pairs arranged) and extra insulation layer! 

> Will it be enough to cause Ethernet performance? Maybe not.  

Removing the outer jacket does not cause problems to 
Ethernet performance as long as you keep the wire pairs 
arranged together as they were with the jacket. 
And you don't put the wire pairs from different cables 
too near to each other (for example keep some mechanical 
separation instead of jackets). 

If you put the wire pairs from different cables without 
outer jackets together, then the performance of the 
cable to cable crosstalk is poorer (more crosstalk) than 
with the installtion where outer jackets are in place. 
This can have effect or not for the system performance. 
This depends on how close to the perfomance limits  
the wiring already was. 

> But will it effect Cat5e performance, absolutely.  If the
> components in this install are Cat5e, I would expect these cables to
> fail the test.

I think that doing the installation where the jackets were 
removed for few centimeters distance and all wire pairs packed 
togehter as shown on earlier posted link, the individual 
cables might well pass the CAT5e performance tests when tested 
individually (if not anymore CAT5e, then most propably still 
CAT5). The perfomance when measuring single cable should have 
not changed radically if no considerable mecahnical damage is 
not done (wire pairs from one cable keep grouped/teisted together 
as they were inside jackets, the cable fasteners not overtightened 
etc..). The only neasurement where I would expect noticeable 
change is cable to cable crosstalk figures. Those are poorer 
than with the installation that keeps the jackets on the wire 
pairs as close to the terminating point as possible. 

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/