Bill VanAlstyne wrote:
"Mark Keith" wrote in message
om...


...As far as the gamma being a poor device that should not be
used, thats hogwash. 1000's have used those things with good results.


Here's a couple questions about gamma match construction:

1) Commercial gamma matches typically employ a gamma rod and integral
coaxial capacitor, constructed of two coaxially mating pieces of tubing/rod
separated by a piece of dielectric tubing. Do you know of any reference that
gives a formula for computing the capacitance of such a coaxial capacitor?

Reference = "Reference Data for RAdio Engineers", Fourth Edition, ITT,
1956, page 134.

[SNIP] C = (7.36 * Er)/(log(b/a))
whe C = pf/ft
Er = Relative permittivity
b = major radius
a = minor radius


2) Antenna modeling programs like YO by K6STI require a specification for
the diameter of the gamma rod. But due to the coaxial capacitor
construction, I'm not sure what diameter is actually being called for. Do
modeling programs typically assume a coaxial capacitor integral to the gamma
rod, or do they assume a molded capacitor between the feedpoint and a
monolithic gamma rod?

Bill / W5WVO