On Sat, 01 Dec 2007 20:28:27 -0800, Roger wrote:

*Here is another way of looking at the coil current.*

Every wave must start with a wave front

Hi Roger,

That, in a sense, sums up what Tom offers at his page (although I am
heavily editing you and outrageously paraphrasing him).

To go even further, and to the matter of measurement, especially in
the problematic use of leads that introduce error; there are TWO ways
for your "wave front" to arrive at the other end of the coil. One is
conduction, the other radiation. To this point in the discussion,
conduction has been the sole consideration (strange too, given the
hysterical outrage over treating the coil as a lumped load that so
often attends this topic).

Clearly radiation arrives by a more direct route, and given the
disproportionate size of the wavelength in comparison to the size of
the coil, the coil is for all intents and purposes transparent to the
propagation of the wave. This is not so for the helix of a TWT, nor
for the deliberate coil design of the helical antenna. However, at 80
meters, any point at the other end of a 10 inch coil is going to be
steamrollered into oblivion.

Tom's commentary hints at this, although the measurement provided is
lacking in detail to support this thesis.

73's
Richard Clark, KB7QHC