"AI4QJ" wrote in
:

....
Owen,

What I did was use the basic impedance calculations:
....

You are performing lumped analysis where the current is uniform through
the coil, and there is no propagation delay.

The other solution that is being discussed is to treat the helix as a
transmission line with distributed R, L, G and C. That is what the
calculator that I gave the link to does. It implements the technique
described by the Corums and others, see the links.

The key thing is that the transmission line solution passes to lumped
elements when the coil length is sufficiently short, so they are not
inconsistent. It is questionable whether the transmission line solution
is worth the trouble for short coils.

Another practice by some is to assert that the helix substitutes
Beta*CoilLength radians of unloaded conductor... but I have not seen a
proof of why that can be done, nor does it seem sensible in the general
case.

Owen

Owen Duffy wrote:
The key thing is that the transmission line solution passes to lumped
elements when the coil length is sufficiently short, so they are not
inconsistent. It is questionable whether the transmission line solution
is worth the trouble for short coils.

That's a Catch-22, Owen. All lumped coils are short.
Therefore, the transmission line solution is never
needed.

A 160m bugcatcher coil is *NOT* short!!!! It is an
appreciable percentage of the delay through the
10 foot long mobile antenna.
--
73, Cecil http://www.w5dxp.com