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Re: wire for random wire antenna using kx3

Posted by Jim Brown-10 on Dec 17, 2018; 9:11pm
URL: http://elecraft.85.s1.nabble.com/wire-for-random-wire-antenna-using-kx3-tp7647146p7647160.html

This overly simplified equation fails to account for proximity effect.

On 12/17/2018 12:58 PM, John Oppenheimer wrote:

> On 12/17/18 1:58 PM, Jim Brown wrote:
>> In order of loss at dB/100 ft at 10 MHz from low to high, the
>> Teflon #12 is lowest at 0.94dB, then RG400 at 1.22 dB (about the same as
>> RG58), then #12 THHN at 1.34 dB. #12 or #10 enameled copper had the
>> greatest loss, 2.4 dB/100 ft.
> Hi Jim,
>
> Two parallel transmission line is the easiest of all to evaluate using a
> RF resistance table and knowing the impedance of the line.
> http://ve3efc.ca/wireohms.htm
>
> The wire loss is dB = 10 * log10((Zo + WireR)/Zo)
>
> Assuming Zo=100 for the #12 Teflon and THHN. R at 10 MHz = 4.24/100 =
> 8.48/200.
>
> Wire dB = 10 * log10(108.48 / 100) = 0.35 dB
>
> Using the two values above at 10 MHz, 0.94 and 1.34, the dielectric loss
> is 0.59 dB and 1 dB. The dielectric loss is about two and three times
> the wire loss.
>
> John KN5L
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