Richard Clark wrote in
news
On Thu, 22 Feb 2007 20:23:49 GMT, Owen Duffy wrote:

Comments appreciated.

Reading:
the note "capacitance from shield to conductor is uniform around
circumference. The capacitance from the inner of the outer
conductor to the outer of the inner conductor acts entirely inside
the transmission line and has no effect on the external balance of
the loop. The conditions on the inside of the loop outer conductor
are isolated from the outside of the conductor due to skin effect
as described above.

I would add a precautionary that the isolation is not complete. There
are many instances of this in small signal designs that fail for this
very reason. I am not sure what you are saying and what you are
repeating because there is no close quote in your commentary.

Sorry about the lost closing quote. Here is the offending paragraph with
the quote fixed and a fuller reference:

====
Another figure in the ARRL Antenna Handbook 18th Edition, p5-6 Fig*8
contains the note "capacitance from shield to conductor is uniform around
circumference". The capacitance from the inner of the outer conductor to
the outer of the inner conductor acts entirely inside the transmission
line and has no effect on the external balance of the loop. The
conditions on the inside of the loop outer conductor are isolated from
the outside of the conductor due to skin effect as described above.
====

Does that clarify it. It is not the greatest bit of prose, but is it
clear enough?

Re the effectiveness of skin effect in isolating the inner and outer, I
agree that it isn't perfect, and less perfect in the case of braid than
for a solid tube. However, even through braid leakage is small relative
to the coupling through the gap as I describe, so the error in
simplification seems small to me.

Thanks Richard.

Owen