Hmmmm, your analysis is interesting. The gamma looks very much like an
"auto-transformer" to me--the gama-rod like a variable primary, the
secondary being the complete driven element.
I suspected the action would be identical to the auto-transformer--where ALL
the turns in the secondary deliver power to the load....

Regards,
John


--
I would like to point out, I do appreciate the "Been there--done that!"
posts. Indeed, now your observations, comments and discourse should be
filled with wisdom--I am listening!!!
"Cecil Moore" wrote in message
...
Cecil Moore wrote:
I knew I was confused about what you were trying to do.

John, I just realized what is wrong with gamma feeding a
1/2WL vertical at the base. The currents in each side of
the gamma feed section are pretty much out-of-phase so
they don't radiate (much). Conclusion: Gamma feeding a
1/2WL antenna at the base results in a field strength
comparable to a 1/4WL vertical and the minuscule amount
of gain is not worth the effort. Antenna gurus probably
already knew that but it just dawned on my concrete brain.

In much the same way a Zepp or a J-Pole is not a 3/4WL
radiator even though they are 3/4WL long, a gamma match
on a base-fed 1/2WL vertical doesn't yield a 1/2WL
electrical radiator. For this reason, the length of a
gamma match should be considerably less than a wavelength.
A good rule of thumb is probably in the ballpark of less
than ~6% of a wavelength. Your idea seems to require about
16% of a wavelength.

Moral: Physical length and RF electrical length are not
always the same.

What you are trying to do apparently requires a J-Pole
or Zepp approach, i.e. a physical 3/4WL antenna.
--
73, Cecil http://www.qsl.net/w5dxp

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