RadioBanter - View Single Post

March 31st 06, 12:31 AM posted to rec.radio.amateur.antenna

wrote:
That's not correct at all Richard. The coil in a TWT tube behaves
considerably different than a small inductor operted at a low
frequency.

A 75m bugcatcher coil is not a small inductor. You guys have
backed so far out of the basic real world argument that we can't
even see your coils anymore without a microscope. Of course,
microscopic coils have delays that can be ignored. 75m bugcatcher
coils are not microscopic. They are HUGE!

How you can argue that the magnitude of the current is the same
at both ends of the coil when 12 out of 13 of the measurements
showed they were different is magical thinking, divorced from
reality.

The only real argument against this seems to be from Cecil, and as I
understood it he thinks standing waves are what causes current to be
different at each end and somehow sets the phase difference between
ends of the inductor.

If you don't understand that fact of physics, you don't understand
the distributed network model at all. In a standing wave antenna,
there exist forward current and reflected current. Any model that
doesn't take that fact into account is doomed to failure.

800 posts later the same major group of people seem to agree, the same
one or two people seem to think something magical occurs in an antenna
making a regular lumped inductor behave like a self-resonant helice
with standing waves and all.

The magic is that current travels through coils faster than the speed
of light. That's what your lumped-circuit argument presupposes. It
also completely ignores reflected waves.

Doesn't it seem logical to use a model that includes reflected waves
when one installs a loading coil in a standing wave antenna?
--
73, Cecil http://www.qsl.net/w5dxp