[BC] Stealth antennas

[Thomas G. Osenkowsky]

Carl Smith examined a tower as a uniform transmission line.
Schelkunoff examined a tower as a non-uniform transmission
line. A larger diameter tower i.e. self supporting tower
occupies a greater surface area at the base, hence a greater
capacitance to ground. The larger diameter is also larger
than its smaller counterpart in comparison to the wavelength.

Recall that an infinitely thin quarter wave radiator above a
perfectly conducting ground with an infinitely thin insulator
has a base impedance of 36+j21 ohms. In practice, the
velocity of propagation, base insulator, height above
imperfect ground, guy wires, etc. produces an impedance
higher than this.

Tom Osenkowsky, CPBE

> I'm always surprised (at myself) when something old becomes "new" again.
> I've known for a long while that radiators with a greater diameter have a
> greater bandwidth than ones with a small diameter. Now, the question I
> should have asked, and answered to myself years ago is: why is this?.....
> If I knew the math behind this in the past I've forgotten it, but just the
> physics for now would do nicely.