Re: NEC-LIST: converting from dBi to RCS

Jim Lux wrote:

>
>
> Are you looking at the actual output file from the NEC engine?
> I assume you've looked at examples 7 and 8 in the NEC2 documentation.
> It says that the column labelled gain is the scattering cross section
> in square wavelengths (i.e. sigma/lambda^2). I assume then, that you
> should be doing something like:
>
> sigma = 10^(gain/10)* lambda^2
>
> No need to square the gain, as you've been doing.
>
> If you are using 4nec2, you need to cross check the value in the plot
> against the value in the actual output file, to see whether Arie has
> scaled it for you already.
>
> Have you run something like the RCS of a conductive sphere? That
> would give you a great analytical comparison.
>
>
>
>
 From Balanis, eq 2-143, the normalized RCS of a half-wave dipole is
supposed to be .86. Working backwards using my equation (with the
square term), I get an expected gain of ~2.1dBi. Using the non-square
equation, I get an expected gain of 4.3dBi. When I use 4nec, I get a
max gain of 2.18dBi, which matches the theoretical results using the
square equation.

Am I doing something wrong?

Thanks
David

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