[TowerTalk] Fields and coax

[Gary]

Roger Parsons wrote:
 > Jim Brown  K9YC wrote:
 >
 >
 >>What do you mean by "perfect?"
 >
 >
 > Exactly that. A 100% coverage, perfectly uniform,
 > perfectly conducting shield which is of course not
 > possible in the real world.
 >
 > If that perfect shield has a finite thickness, which
 > it has to have in the real world, there will be an
 > external field. Actually, to really, really nit-pick,
 > unless the cable has an infinite diameter!
 >
 > As I implied in my earlier post, this field will be
 > very small, but not quite insignificant for the most
 > sensitive applications, with an excellent (but real)
 > cable, and is not related to imperfections in real
 > world manufacturing processes.
 >
 > This is incidentally not the effect you described
 > earlier concerning audio frequencies.
 >


Look up "transfer impedance" on google. It makes for some interesting
reading. It is also how lightning energy gets onto the center conductor
of a cable that has a grounded antenna or short at the antenna end of
the cable.

73
Gary  K4FMX