[AMRadio] Re: new antenna and matchbox a bust.

John Lawson jpl15 at panix.com
Tue Jan 30 23:14:53 EST 2007

On Tue, 30 Jan 2007, Geoff/W5OMR wrote:

> In Brett's case, if it were two runs of copper wire inside ONE shield, do you 
> think -that- would be better?
> Why? 
> What's the difference?

   The thing is, it's *not* two wires in one shield - it's two pieces of 
coax, adjacent at some distance of the center-conductors, both shields 
grounded at both ends of the run (IIRC).  Currents are bound to be induced 
in the shields, especially at the (possible) nodes, and it's possible that 
these currents can be significant (read: affect the operation/performance 
of the system) in physical places along the run of the two coaxes.

   I think the point of contention in this discussion is: "what do you get 
when you operate adjacent/parallel coaxial cables as a balanced conductor, 
given that the shields are connected to ground at both ends of the 
hypothetical run...   what are the parameters and effects at various 
frequencies? Signal levels? Physical length?

   And I'm poking thru a few resources, trying to come up with 
peer-reviewable answers to these questions. Quite likley there exists a 
cogent and simple exposition of this - I just ain^H^H^H^H  have yet to 
have found it.

   And, in the process, I'm most likely boring the hell out of the majority 
of the AmRadio List....


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