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Old May 6th 09, 11:35 PM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Mar 2007
Posts: 3,521
Default Dual-Z0 Stubs

John KD5YI wrote:
I think any inductor with the same inductance, Q, and self-resonant
frequency will give the same velocity factor and delay as your
Bugcatcher.


That may or may not be true - I don't have an
opinion one way or another - and it is NOT part
of my argument. My argument deals only with
75m Texas Bugcatcher coils and other large air-
core loading coils used on 75m.

My argument is that the velocity factor of a 75m
Texas Bugcatcher coil is ~0.02, occupies ~41
electrical degrees on 4 MHz, and exhibits a
delay of ~28 nS through the coil. That is my only
argument. I am not interested in diversions from
that argument.

My argument also includes the 100 turn, 10 inch long,
2 inch diameter coil that w8ji used for his 3 nS delay
"measurements". If he had used traveling wave current
for the measurement, he would have measured approximately
25 nS.

Maxwell's equations for slow-wave structures (like
a 75m Texas Bugcatcher loading coil) are given in
"Fields and Waves ...", by Ramo and Whinnery:
pages 467-479 in the 2nd edition. This is one of
the references in the Corum IEEE paper.

What do you make of Roy's (w7el) statement at:

http://www.w8ji.com/agreeing_measurements.htm

"As described in my posting on rraa of November 11,
the inductor 'replaces' about 33 electrical degrees
of the antenna."
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com
 
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