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Date: Thu, 07 Mar 2002 17:41:38
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: RE: Re: loops
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Hello Bill,

I following the discussion on loop antennas with great interest. I'm far
from a specialist, but trying to learn ...

>What really looks interesting for a loop installation, according to the
>math, is the effective power gain that can be achieved by stretching the
>horizontal dimension. On my property I can make this 350ft (if it were
>legal) because of this strange narrow "L" shape out back in the woods.  The
>effective power, then, increases 50x! Tried this for an hour at very low
>power (don't tell the FCC), and it works!

What math do you use ?
I dug up a formula for small loops (I suppose any ham-sized loop is 'small'
at 2.2km / 1.33mi wavelength) :
R = 320*Pi^4*A^2/L^4 , where R = radiation resistance in Ohm, A = loop area
and L = wavelength.
So based on that a 10m high and 100m long loop should perform as well 32m
high square loop. Doubling the length of a long&low loop should increase
the radiation resistance by 4 and the loss resistance by 2, resulting in an
overal gain of 2 (= 3dB).
Does the above fit with your math ?

I like the idea of an L-shaped loop ( I suppose you mean lazy-L, so the
loop is not straight in the vertical plane) as I presume that this will
reduce the sharp nulls in the radiation pattern.
>
>My first TX loop article just appeared in the US Longwave Club's 'Lowdown'
>publication. The second is to follow next month.
Sounds interesting, is it available on the web ?


73, Rik  ON7YD