[time-nuts] Quadrifilar Helix Antenna

[Azelio Boriani]

Yes, you are right and this is the problem I have. I'm aware that wonderful
things can be done starting with a simulator, not just tell whether or not
the antenna will be on frequency. I have to fill the gap and learn how to
successfully use a simulator.

On Sun, Jun 10, 2012 at 12:03 AM, David Kirkby <david.kirkby at onetel.net>wrote:

> On 9 June 2012 15:53, Azelio Boriani <azelio.boriani at screen.it> wrote:
> > Of course one of the most challenging part of the EM simulators is
> > preparing the correct model of the structure you want to simulate.
>
> Agreed.
>
>
> > Unfortunately (for me) I'm mostly a try-it guy rather than simulate-it
> so I
> > prefer to build and try with test equipment. My first QFH was too high in
> > frequency (GLONASS-ready?) so I have to build another one.
>
> But there are obvious advantages to being able to model something
> first, especially in a case like this, where there is nothing I see to
> indicate this is optimised in any way. So it might be possible to
> improve on it. Experimentially determing if something is on frequency,
> and if not making another is not that hard, but knowing how various
> changes might affect the radiation pattern is less easy to predict.
>
> If you can accurately model the one you built, you might get some idea
> about other changes that could be made. I doubt the EM simulation
> tools will get the frequency spot on, but I find they give me insight
> into the problem.
>
> At this very minute I'm running a simulation of a 7 turn axial model
> helix antenna with a view to determine if the use of steel would give
> significantly poorer performance than copper. You would probably have
> a hard-time measuring the differences, and its a lot cheaper to just
> re-run a simulation than to build two of them and measure them.
>
> Dave
>
>
> >
> > On Sat, Jun 9, 2012 at 4:11 PM, David Kirkby <david.kirkby at onetel.net
> >wrote:
> >
> >> On 8 June 2012 09:31, Raj <vu2zap at gmail.com> wrote:
> >> >
> >> > I came across this article. I dont understand Italian!
> >> >  From RadioKit Elettronica 2003-03
> >> >
> >> > https://dl.dropbox.com/u/10377704/IV3QBN%20QuadHelix.pdf
> >> >
> >> > Cheers
> >> >
> >> > --
> >> > Raj, VU2ZAP
> >> > Bangalore, India.
> >>
> >> I'd be interesting in trying to see some simulations of this in a full
> >> wave 3D electromagnetic simulator like HFSS from Ansys, FEKO, EMpro
> >> from Agilent etc. I currently have a trial license for Agilent's
> >> EMpro, but don't feel confident in trying this antenna. I would have
> >> been a bit happier using HFSS, but don't have a license for it.
> >>
> >> Maybe one of the much cheaper NEC based programs coud do this, though
> >> I'm not so sure I'd trust the results, whereas I would from HFSS.
> >>
> >> HFSS (which costs a small fortune), comes with a free antenna design
> >> kit. That is able to design a Quadrifilar Helix Antenna, but needs a
> >> ground plane, so has a very different radiation pattern to this.
> >>
> >> Dave
> >>
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