Re: Helical Antennas

Your comment is very reasonable - normal mode helical antennas would be
better modeled by NEC. When the higher modes of the helix come into play
(T1, T2 modes) for long helices, the so-called "axial mode" is poorly
modeled. Results tend to be increasingly optimistic for increasingly long
helices. I can not say how accurate normal mode modeling would be, but
since the directivity is so low, I'd expect the error to be less than a
dB at boresite.

On Fri, 9 Aug 1996, Feng Niu Research wrote:

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> I would like to hear more comments on this subject. I cannot see why
> the NEC-like modeling does not apply to helical antennas at least in
> the normal mode (small antennas, for example) where they act more like
> short dipoles.
>
> My question is:
>
> Does NEC apply at least to some helical antennas, and any
> benchmark solutions have been done to quantify how acurate the NEC solutions
> are for helical antennas?
>
> Feng
>
> On Aug 8, 7:56, builder#064#cais.com%INTERNET_at_email.mot.com wrote:
> > Subject: Re: Helical Antennas
> > My masters thesis was a study of helical antennas, and the building of a
> > prototype helical array (hooray for me ...). I found that NEC was 100%
> > unreliable for helical antennas in both the so-called axial and normal
> > modes. It has to do with the fact that the helical antenna acts as a
> > waveguide structure that does not lend itself to NEC-like modeling. Kraus
> > and some others tried to characterize helical antenna gain using NEC-like
> > methods (actually closed form solutions), resulting in gross
> > overestimates. Some really good work was done by Aerospace Corp (King and
> > Wong) in the 1970's (?).
> >
> > On Wed, 7 Aug 1996, Mike Slater wrote:
> >
> > > I would appreciate any information pertaining to
> > > helical antenna performance using NEC. I have heard
> > > some remarks about NEC not being reliable, however,
> > > I have not been able to find any literature,
> > > results etc. that support or refute these claims.
> > > If anyone has any info/suggestions/links I would
> > > greatly appreciate any information.
> > >
> > > Thank you.
> > >
> > >
> > > Mike Slater
> > > mike_s_at_ece.concordia.ca
> > > mike_s_at_pils.com
> > >
> > >
> >
> >
> >-- End of excerpt from builder#064#cais.com%INTERNET_at_email.mot.com
>
>
>
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Received on Fri Aug 09 1996 - 16:10:00 EDT