Re: NEC-LIST:an easy one

It gets a little messy to write in its expanded form, but it's easy to
derive from the following: Attenuation in nepers per meter is
Re(Sqrt(-omega^2*mu*epsilon + j*omega*mu*sigma)), where
 
  omega = radian frequency
  mu = permeability of medium
  epsilon = permittivity of medium
  sigma = conductivity of medium

All the above of course have to be in MKS units for the result to be
nepers per meter. A good analysis can be found in Chapter 10 of Kraus,
_Electromagnetics_.

I calculate 9.08 dB/m for your example. In my experience, evaluation of
attenuation of plane waves in the NEC-4 ground medium closely follow
results calculated by this formula.

Roy Lewallen

Grant Bingeman wrote:
>
> When an EM wave is propagating through some medium other than air, such as
> earth, what is the formula that relates earth conductivity (S/m) and
> dielectric constant to loss in dB per meter?
>
> for example at 100 MHz and epsilon = 3.0, the 10 mS/m loss is about 9 dB/m
>
> Grant
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