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Old April 20th 06, 02:51 AM posted to rec.radio.amateur.antenna
Cecil Moore
 
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Default Current across the antenna loading coil - from scratch

Gene Fuller wrote:
Oh darn! There's that nasty reference to "resonator" again. You really
need to read the paper again and attempt to understand it.


Uhhhhh Gene, a 75m bugcatcher coil is a "resonator" that
resonates an 8 foot mobile antenna on 75m. Take a look at
Figure 2 in Dr. Corum's paper. It looks just like a top-
loaded 160m mobile antenna.

Try the left-hand column on the page for the fundamental mathematical
limitation that underlies everything else on the page, including Figure 1.


There is a test equation to see if a particular coil is
outside the fundamental mathematicdal limitations. A 75m
bugcatcher coil is less than half the limit value.

Let me show you how to use Fig. 1. The coil that we have
been discussing is 6 inches in diameter and has 4 turns
per inch. That makes D/lamda = 2.0 x 10^3. That's just
about in the middle of the graphic. The turns per wavelength
is 48*246 = 11,808. That's just to the left of the left
hand curve. Reading the velocity factor from the graph
gives about 0.03 for that coil. It's a piece of cake
if you understand the physics involved.
--
73, Cecil http://www.qsl.net/w5dxp