well, you have a point, the coax cable if it is ideal it will work as
somebody described earlier in that treed, but unfortunately life is
real, and therefore despite that the E and H field is mostly "inside of
the cable", but due to the cables loss particularly because braid has
resistance there will be a voltage between the two end of the cable's
shield. And that is related to a "mess" called transfer-impedance, and
about that you could find really interesting explanations like that:
https://spira-emi.com/references/pdf/tf4_cables_cntrs_hoeft.pdf and
thathttps://www.araconfiber.com/what-is-transfer-impedance/ and much
more, because that transfer impedance is a big headache for people who
are sending signals trough coax cables, and above a certain frequencies
the coaxial cable is not a "such a good thing" any more.
Just one very malicious note, that works reversible too: if you would
inject a signal to that braid's two ends, the signal would show up like
is it's source would be serial with the generator which is driving
"legally" the cable in "coaxial" mode. I know it is very nasty but it is
true, I found it out myself also some sixty-five years ego, and a whole
world of ideal system just collapsed at the front of me...
KJ6UHN
Alex
On 7/5/2019 10:47 AM, Peter Vince wrote:
On Fri, 5 Jul 2019 at 18:01, WigglePig <[email protected]> wrote:
If there are currents in the braid to upset then your antenna system is
not working as you might believe.
I was working on the simplistic assumption that for a current to flow,
there must be a complete circuit, so the current flows down the centre
conductor, and must come back up the braid. But I gather that unlike DC,
RF is "black magic", and only flows on the inside of the braid - if all the
impedances match.
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