[sts9fan]

So I have some nice STP wire and was wondering if it is ok to use without grounding the shield?  Will this add noise? 

Thanks 
Kris

[Daryl]

Normally you will ground one end of the shield and not both as differential signals between the componets at each end could cause current signals through the shield which might be induced in the signal wires.

If you have ground lift switches at either end of the connection you can experiment to see which of the four options results in the lowest noise level.

You can certainly achieve respectable performance with the sheild unconnected as a twisted pairs benefit is that it is far more resistant to interference than a coaxial cable which excels at high frequency performance.

A grounded shield will improve upon the twisted pairs already impressive performance.

To get the best performance with twisted pairs you want to drive them from a true differential (balanced) source.

A twisted pairs conductors when driven by a differential source have an average voltage of zero making capacitance from conductors to shield not figure into cable capacitance leaving capacitance between the twisted pair as the major issue (cable capacitance is higher when you drive it with a single ended source).

[BobM]

What do you want to use these for?
 - interconnects
 - signal path wiring within a component

(1) For interconnects I believe the general rule of thumb is don't use shielding unless you find you need it, then only ground one end of the shield (usually at the end where you want the crap to drain to).

(2) I don't know that an ungrounded shield would make much of a problem in practice, but I guess theoretically it could act as an antenna and pick up some stray crap in your environment; but if your environment is clean to begin with then it's probably not a real problem (see #1).

(3) For a signal path inside of a component I think it would always be wise to use a shield if you can. There's a lot of stuff bouncing around inside a component case and isolating the signal path from that noise (most usually on the ground plane) is a good idea.

Enjoy,
Bob

[sts9fan]

Thanks for the info guys.  Once again I post tool little info in my question.  I will get it one of these days.
I am going to use it for my gainclone which is about to be finished!  Finally a project is coming to a completion!