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Old March 12th 06, 02:13 PM posted to rec.radio.amateur.antenna
Cecil Moore
 
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Default Radiation Resistance

Reg Edwards wrote:
I am not trolling.

What I want to know is the radiation resistance, referred to the base,
of a short vertical wire above a perfect ground, the current in the
wire being assumed uniformly distributed.

The radiation resistance at the base is in the form of -

C * Square( Length / Lambda )

where Length is the physical length or height of the wire and Lambda
is the free-space wavelength.

What is the value of the constant C ?


Reg, I believe it would be 10*pi^2 = 98.7, half of the
value of a small dipole. Balanis gives a dipole a very
thorough treatment and then says the monopole is half
of those values. His constant in the value of radiation
resistance for a short dipole is 20*pi^2. Kraus rounds
that constant off to 200. That value assumes the short
dipole is not infinitessimal and has a linear standing
wave current distribution. That constant doesn't seem
to need to be a very exact value.
--
73, Cecil http://www.qsl.net/w5dxp