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From: "Ashlock,William" <William.Ashlock@edwards.boc.com>
To: rsgb_lf_group@blacksheep.org
Subject: LF: 47A of loop current: No sweat!
Date: Fri, 28 Jun 2002 18:05:37 -0400
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Mal and group,

I was just pricing out various sizes of copper pipe at the local builders
department store for the next "dream" (or is that "pie in the sky"?) loop
antenna. Turns out 2" ID pipe is $18 per 10 ft section which would yeild a
0.04ohm Rac on a 50'x50' loop, neglecting soil loss. Was actually
contemplating reducing the size to about 1/4th the area to allow raising and
lowering the loop to  measure various losses without a reduction in the
basic radiated power @ an input of 1w. 

Then I did a little 'wild math' (or call it 'wildfire' math) to determine
the dimensions of a 47A loop (still at 1w to keep it legal) that would have
the same radiation as my 50'x50' 1/2" pipe loop. Considering my present
1.8A, going to 47A would allow a 47/1.8 = ~25x reduction in loop area. The
new area would be 2500/25 = 100sq ft or 10ft per side. So far, so good. But
in order to achieve 47A @ 1w the Rac of the new loop would have to be
1/(47^2)= .00045 ohms. I did a bit of manipulation of the formula for Rac Vs
conductor diameter for a 40ft long copper conductor and came up with:
Diameter (in inches) = .016/Rac. Using an Rac of .00045 the diameter comes
to 35 inches. Well.... not impossible! And could be fashioned from .01"
thick copper foil - maybe $200 worth! 

Just thought you might want to know......

TGIF!

Bill A    

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