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Old September 15th 09, 10:11 PM posted to rec.radio.amateur.antenna
Richard Fry Richard Fry is offline
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First recorded activity by RadioBanter: Jun 2006
Posts: 440
Default Spherical radiation pattern

On Sep 15, 2:53*pm, Art Unwin wrote:
When you do your fancy playing with EZNEC you will notice
that as the impedance goes down the radiation increases.


Art, below to help you analyze your belief is a link to the calculated
radiation efficiency for a system with a perfect, base-driven,
monopole radiator using an r-f ground better than that used by most AM
broadcast stations.

The system is brought to resonance with a loading coil. The feedpoint
impedance is 4.1131 +j0 ohms, of which the radiation resistance
component is ~ 0.1 ohm.

So if, as you write, reducing feedpoint impedance increases radiation,
what do think accounts for this extremely poor system efficiency
(2.75%), compared to the ~ 95% system efficiency typical of a 1/4-wave
monopole using that same r-f ground?

http://i62.photobucket.com/albums/h8...AMBestCase.gif

RF