[time-nuts] Comparison of Logic Standards for Clock Distribution

James Maynard james.h.maynard at usa.net
Tue Oct 24 12:35:25 EDT 2006


Stephan Sandenbergh wrote:
> 
<snip>
> .... However, faster edges give rise to various problems
> such as crosstalk, EMI and reflections&ringing. I guess that another
> approach would be to differentially transmit the clock in sinusoidal format
> where after it is heavily filtered and squared at the receiving end. Now,
> one would have less transmission line problems but also less noise immunity.
> 
The way to minimize reflections and ringing, methinks, is to terminate 
your cable with its characteristic impendance. A 50-ohm coax is called 
that because a long length of that coax acts like a 50-ohm resistor. So 
if you terminate the coax with a 50-ohm resistor, the cable "thinks" it 
is terminated with an infinite length of the same coax. Hence, no 
reflections, no standing waves.

-- 
James Maynard, K7KK
Salem, Oregon, USA




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