> -----Original Message-----
> From: towertalk-bounces@contesting.com [mailto:towertalk-
> bounces@contesting.com] On Behalf Of Jim Lux
> Sent: Wednesday, July 12, 2006 11:56 AM
> To: Michael Tope; JC Smith
> Cc: towerTalk
> Subject: Re: [TowerTalk] TT SHUTDOWN (was: 4 awg copper wire and Amp
> locks)
>
> At 07:41 AM 7/12/2006, Michael Tope wrote:
>
> >----- Original Message ----- From: "Jim Lux" <jimlux@earthlink.net>
> >
> >>
> >>
> >>>I wonder... if you roll (the long way) copper strap you could put it
> inside
> >>>hose. As long as the inside circumference of the hose was greater than
> the
> >>>width of the strap you wouldn't be forming a tube with the strap. What
> if
> >>>you slit the copper tube before using it, would that be enough to allow
> both
> >>>the inside and outside to conduct high frequency current?
> >>
> >>There's no reason why you couldn't propagate current on the inside of
> the
> >>pipe without slitting it. That's what happens in coax.
> >
> >Not without a center conductor. Otherwise you'd have a waveguide
> >beyond cutoff.
>
> Only if you're propagating the wave in a transverse mode. DC is below
> cutoff, but it's carried on the inside(as well as inside the metal,
> etc.). The question might be, if you have a seamless tube, and you have a
> current on the inside, will the magnetic field push it to the outside. An
> interesting problem.
>
If the shield of a coax cable carries a lightning strike about half of the
energy gets transferred to the center conductor of the cable and propagates
down the cable just like a radio signal would. This includes the propagation
delay caused by the velocity factor of the coax.
The energy gets inside the coax from the low frequency and DC energy carried
by the shield. This penetrates, as the skin effect falls apart, where the
skin effect would normally keep it on the outside. The field that is now on
the inside of the cable gets induced onto the center conductor.
The effect is called transfer impedance.
However if there is no center conductor in the pipe the high frequencies
will not be able to propagate down the inside and will die out.
73
Gary K4FMX
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