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Old March 23rd 06, 02:52 AM posted to rec.radio.amateur.antenna
Cecil Moore
 
Posts: n/a
Default Current through coils

wrote:
The point I (and others) tried to make was that in a small inductor
current was essentially equal at both ends of the coil, ...


A 75m bugcatcher coil is NOT a small inductor. It is a slow-
wave structure with a velocity factor of about 0.017, both
measured and calculated. That gives my bugcatcher coil an
electrical length at 4 MHz of about ~60 degrees.

This is because the inductor does not replace a certain "electrical
degrees" and have a cosine current drop related to those degrees.


Sorry, Tom, Dr. Corum has proven you wrong on that score. A 1/2WL
thin-wire dipole has a perfect cosine curve. Other structures
deviate away from that perfect cosine curve. The coil certainly
deviates away from that perfect cosine curve. But if you look
at the current waveforms at:

http://www.k6mhe.com/n7ws/Loaded%20antennas.htm

figure 3, you can still see the outline of that cosine curve.

I can take an antenna of specific height and vary current taper in the
inductor quite a bit just by changing the style of loading coil.


You can take the same loading coil and move it around in a standing
wave environment and obtain any current distribution including current
flowing into both ends of the coil at once.

It is the idea that the loading coil drops a certain current because of
"electrical degrees" that is so untrue.


Sorry, Tom, that's just an old wives' tale of yours. Please respond
to my new thread, "Silence of the Gurus".
--
73, Cecil http://www.qsl.net/w5dxp