Richard Clark wrote:

On Sat, 25 Mar 2006 01:53:24 GMT, "W. Watson"
wrote:


Ultimately, I'm trying to comprehend, via a proof, that two receivers
separated by a distance D can act as though they are a single receiver of
size D. Perhaps it can be done by simply considering the Young double slit
experiment. It bothers me that the idea is passed along without ever proving
it. Maybe the proof is trivial.


Hi Wayne,

The two receivers/antennas is called "synthetic aperture." You can
observe the same thing with one antenna that is moving, we commonly
call it "picket fencing." This effect is due to reflections and
direct signals interfering constructively and destructively as you
move through the interference field. The math for that alone is found
in "Fresnel loss."

The Young double slit IS the proof in that it contains all the math
you need. It contains two transcendental operations (sin or cos) as
many thetas as there are phases and distances, some magnitude
information, and the result pops out at you.

In fact, the math is all the same for all of these effects.

73's
Richard Clark, KB7QHC
My *old* physics book doesn't give the proof, but Hecht's Optics does.
Whoops. It's in Waves by Crawford. No mention though that is the proof of
this particular fact. Hecht mentions the experiment, and it may be proven in
subsequent sections using Fourier methods. Waves does it the old fashioned
way. Accepting your comment then, I can read through it with a little more
attention. Thanks.


Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet
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