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Old March 12th 04, 05:19 PM
Radio913
 
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If you put the array on a rotator and put a receive antenna with some
sensitive output indicator beyond the near field, you can plot relative
field, and thus accurate F/B by adjusting the power to the antenna for same
received F/S at, say, 10º increments. Nothing else should change, so the
relative field strength in the various directions should relate to each
other. Ground reflections and absorption, and all the other artifacts will
be constant unless you change something else.


ok, that sounds like a good idea, with the rotator, keeping everything else
the same. This site:

http://radioproshop.com/antennaconcepts.htm

Says that the near-field is defined by Rmin=(2*D**2)/wavelength, where
D is the largest dimension of the antenna. So if we roughly say one wavelength
is 10 feet, and the largest dimension is the dipole, then we get Rmin=5 feet,
or about a 1/2 wavelength. This sounds a bit too close to me, perhaps the
far-field is better defined as, like, ten wavelengths or so?


Also, i don't really have a transmitter that I can vary the power that
much...maybe that's something i should make or get. Something variable at
least by 20dB or so.


Slick

 
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