Re: NEC-LIST: quick and dirty vertical antenna model hack?

Roy Lewallen wrote:
> That approach works only with perfect ground, so you won't get a
> realistic pattern. If you attach the monopole to a Sommerfeld or
> reflection coefficient ground, you get an unpredictable resistance.
> EZNEC handles just this kind of situation by providing a "MININEC-type"
> ground. This treats the ground as perfect during the impedance and
> current calculations, but uses the finite ground conductivity and
> permittivity for pattern calculations. This corresponds to an antenna in
> a real earth environment but with a lossless ground system. Realistic
> ground loss can be included as you suggest, with a resistive load at the
> antenna base.
>
> Other commercial programs might also have this feature. You can get a
> free EZNEC demo program to try out from http://eznec.com.
>
> Roy Lewallen (EZNEC developer)
>
> Jim Lux wrote:
>
>> Say one wanted to model some arrays of 1/4 wave vertical monopoles and
>> include an approximation of the ground losses, etc.
>>
>> Would a reasonable hack be just to put a resistive load of a few ohms
>> into the bottom segment of a vertical attached to the ground plane?
>> (as opposed to exhaustively modeling the actual grounding network).
>>
>> I'm looking at modeling some "forests" of verticals, and I'm more
>> interested in the mutual Z effects vis a vis feed networks (which I'm
>> doing with NT cards) and the influence on the patterns that result
>> than in agonizing over precise grounding models.
>>
>>
>> James Lux, P.E.
>> Spacecraft Radio Frequency Subsystems Group
>> Flight Communications Systems Section
>> Jet Propulsion Laboratory, Mail Stop 161-213
>> 4800 Oak Grove Drive
>> Pasadena CA 91109
>> tel: (818)354-2075
>> fax: (818)393-6875
>>
>

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