Re: NEC-LIST:Parabolic Dish Wave Impedance

Kenneth,

Without much thought, my view is that the impedance of the horn looking
into the dish will be very close to the impedance looking into free
space. Use an offset feed if you want a uniform field in the near field
of the reflector: Like an indoor range. Do not illuminate the apex plate
heavily.

Regards,

Kenneth Webb wrote:
>
> Hello all.
>
> I am considering using a parabolic dish antenna for radiated susceptibility
> testing. The antenna range in question (at this point) is 1-2GHz. The field
> levels obtained thus far indicate a very efficient radiator. The feed horn is
> slightly offset so that the focal point is just below the feed horn.
> Recently, someone asked if the wave impedance of the standard gain horns used
> in this area (and a large reverberation chamber) are the same as the parabolic
> dish reflector.
>
> Without going to my antenna books and NEC 4 program to simulate the impedance,
> I was wondering if someone might have some insight into this question.
>
> Thanks in advance.
>
> Kenneth John Webb
> Principal EMC Design Engineer
> --
> The NEC-List mailing list <nec-list_at_gweep.ca>
> http://www.gweep.ca/mailman/listinfo.cgi/nec-list

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