--- enorbet  wrote:

> >
> Thanks Ralph
>   Now *that* is really interesting.  I know that with analog cabling 
> electrical signals tend to travel along the surface of the wire, 
> especially higher frequencies, so that many fine strands are superior
> to 
> a single massive one especially if the resulting surface area is
> greater 
> ( which it almost always is in real world application ) because of 
> multiple stranding.  It really makes me wonder as to why the degree
> of 
> twisting has such a profound effect on digital transmission
> especially 
> considering that it would seem that comparing two otherwise identical
> 
> cables, the one with the greatest amount of twist will be some 
> percentage longer than one with fewer twists. Anybody know why this
> is 
> so?  Assuming just this one design factor is important to network
> data 
> transmission I think Ralph is probably right in his inference that 
> mutimedia may also be profoundly affected.  It may even shed some 
> additional light on the recent move away from parallel cabling and 
> interfaces toward serial connections.  Fascinating!
> Jimmy

I'm sure it all has to do with magnetics, induction, impedence, and
capacitance. All electrical flow creates a magnetic field, analog and
digital transmissions constantly change voltage and therefore cause
that magnetic field, the field induces voltage in adjacent wires, and
the variance of twists must change the optimum impedence to it's
capacitance at a given frequency. It may not be the frequency of what
the twisted pair is carrying, but the frequency of magnetic fields the
twisted pair must run close to that needs to be filtered out so that
the signal stays clean. (That's my convoluted theory!)

Kind of like the old television flat antenna wire (300ohm impedence 2
conductor flat cable with the conductors about 1 cm. apart). By
twisting the cable down the pole and to the television, it could
improve picture quality by filtering out house current, radio waves,
etc.

Franklin


		
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