Re: NEC-LIST: losses simulation

Hi Roy and all,

Basically what is happening with very close turn helix's is that you are
violating the "thin wire kernel" that is used in NEC, ASAP, and many
other programs. However, for a bit wider helix's, ASAP performs very
well, as it has been used very successfully for radio astronomy (I have
no idea what they are doing though). See Ray Cross's homepage for the
FORTRAN version which will go fast with 16 segments/turn. By fast I
mean like an hour sim with 5,000 segments :) You will need to set the
maximum segments before compiling.

Here it is: http://home.att.net/~ray.l.cross/asap/index.html

Rob.

Roy Lewallen wrote:
>
> Yes, that's correct. But be aware that if you space the turns very
> closely (less than a few wire diameters), the real antenna wires will
> exhibit a higher resistance due to proximity effect that's not accounted
> for by EZNEC/NEC.
>
> Roy Lewallen
>
> ROSSI Giuseppe wrote:
> > Dear all,
> > I wish to submit a question concerning the NEC capability of simulating
> > losses.
> >
> > I wish to build a small (compared to the wavelength)dipole
> > for a the radioamateur band of 1.8 MHz.
> > To such a purpose i wish to use helix in the normal mode: a dipole with the
> > two arms
> > made of wounded wire.
> > The idea comes form the book "small antenna".
> >
> > In order to have some idea about the functionality of this kind of antenna I
> > start
> > playing around with elix in NEC.
> >
> > The question is the following: to evaluate the losses of an antenna I start
> > doing the simulation (with EZNEC), first with the antenna made of copper
> > wire, than with the antenna made with Zero losses option.
> >
> > In both the cases i measure the real part of the input impedance.
> >
> > Is it consistent to say that the input resistance of the case with zero
> > losses option
> > is the pure radiation resistance of the antennna?
> > Hence subtracting this value from the input resistance with copper wire, I
> > get the antenna
> > resistance losses.
> >
> >
> > Thanks to all
> >
> >
> > IZ1BLH
> --
> The NEC-List mailing list <nec-list_at_gweep.ca>
> http://www.gweep.ca/mailman/listinfo.cgi/nec-list

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