Date: Sat, 16 Mar 2002 15:16:36 -0800 (PST)
From: "John Sexton" <computernetworks@go.com>
Subject: Re: LF: TX Loop antenna conductors
To: rsgb_lf_group@blacksheep.org
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Hi Bill,

I find the usual formula for the ratio of Rac/Rdc = d*sqrt(mu*f/rho) very unsatisfactory for small diameters, since as d gets smaller the ratio cannot get less than 1. The same is true for low values of frequency. Instead I use a couple of series approximations to the Bessel functions.
So I checked your figures and found for AWG #12 at 185kHz, a ratio of 3.6 and for #8 a ratio of 5.56, quite close but slightly higher than your figures. 

The point you made is of course why it is better to use properly made Litz wire to keep the advantage of thicker wire.

73, John, G4CNN

-----Original Message-----
From: "Ashlock,William"<William.Ashlock@edwards.boc.com>
To: rsgb_lf_group@blacksheep.org
Date: Sat Mar 16 12:32:42 PST 2002
Subject: LF: TX Loop antenna conductors

>All,>
>I get a bit perturbed when I see comparisons of various loop conductors
>using Rdc values since the 'skin effect' within the conductors causes the
>Rac to be much higher at the frequencies we use.
>
>To prove the point, I calculated the 'skin effect' of two different loop
>conductors. For #12  (2.05mm) at 185k the Rac/Rdc came out to 3 and for #8
>(3.26mm) the Rac/Rdc was 5.  Even though the Rdc for #8 is over 2.5 times
>lower than #12 for the same length, the Rac is only about 35% lower. This
>amounts to  a mere 2.6db signal improvement, assuming no soil loss. With
>typical soil loss factored in, the signal improvement would be less than 2.2
>db. 
>
>Bill A 
>
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