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Old May 8th 07, 12:46 AM posted to rec.radio.amateur.antenna
Jim Kelley Jim Kelley is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 666
Default Phase Shift through a 75m Texas Bugcatcher Coil

Cecil Moore wrote:

Jim Kelley wrote:

As a suggestion, you might consider increasing the current for the
EZNEC simulation on your webpage.



Done as you suggested by changing the current amplitude scale.
What do you think about the simulation? Stand by for more
additions to that web page.


From what I gathered, the objective of loading the coil with its
characteristic impedance was that there would be no reflection. I was
therefore surprised when you reported something other than a straight
line for the current amplitude along the radiator (let alone an
increase at some point). It is now apparent that what you are
actually plotting is the superposed forward and reflected currents,
and that you have somewhat more than a negligible amount of reflected
current.

The primary utility in looking at the standing wave profile lies in
the fact that it gives an idea of what the superposed field intensity
plot might look like in the near field of the antenna. But it is
obviously the currents associated with waves traveling on the antenna,
both forward and reflected, that actually do the radiating.

I agree with you that it is useful to understand the exact effect the
loading coil has on the traveling wave, and hence the standing wave
profile of the antenna. But I still think it would be prudent to
explore and understand the precise nature of the delay through the
coil more thoroughly before making too many assumptions about this.

73, Jim AC6XG