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.kir...@onetel.net>wrote: > On 9 June 2012 15:53, Azelio Boriani <azelio.bori...@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.kir...@onetel.net > >wrote: > > > >> On 8 June 2012 09:31, Raj <vu2...@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 > >> > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@febo.com > >> To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > >> > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.