Ernie, in response to your question regarding the effectiveness of coax at noise suppression/rejection:

Basically, the outer shield has a low-impedance connection to the chassis grounds of the connected equipment. Induced noise is thus shunted to ground, sparing the delicate signal conductor within. This principal applies to any shielded cable.

By the way, noise induced into an UTP is not of oppostite polarity on each of the two conductors! On the contrary, it is of the same polarity, and idealy the same magnitude and in phase (one reason for the tight twisting). It is the signal itself which is delibrately inverted on one of the conductors during transmission. The signal of each conductor mirrors that of the other, hence the term "balanced." This principal is central to the ability of balanced transmission systems to successfully reject noise. The differential receiver (or balun transformer) is sensitive only to the *difference* in potential between the two conductors. Because induced noise is induced equally on both conductors, it is rejected.

This message was edited by M_Bruno on 08/09/03 18:58.