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Old April 23rd 07, 05:05 AM posted to rec.radio.amateur.antenna
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Default Measuring Antenna Efficiency
(Richard Harrison) wrote in news:10571-
:

Jimmie D reported Roy Lewallen to write:
"There is no direct way to measure the total power being radiated other
than sampling the field at many points in all directions and
integrating."

That sounds right to me. An approximation is sometimes made by taking
36
samples of field strength in volts per meter at 10-fegrees of azimuth
intervals at the same distance from the central antenna system. Each of
these sample values is squared and the sum of these squared samples is
divided by 36, the number of samples, to get their average. The square
poot of this quotient is then the average field strength at that
distance from the antenna. A true average signal strength should be the
same as the value an isotropic antenna would radiate at a given
distance.

Is that true?

Firstly you seem to assume that your 36 samples around the azimut circle
adequately fulfill Roy's "sampling the field at many points in all
directions", surely he mean't all elevation angles as well as all azimuth
angles.

Secondly, your suggestion that the average field strength (presumably for
a 100% efficient antenna) at zero elevation is the same as for an
isotropic antenna at the same distance seems to preclude the antenna
having directivity in the elevation dimension.

Owen
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