NEC-LIST: modelling of whip antenna

I am currently looking to the problem of analysing a so-called whip antenna.
It is, as I understand it, a monopole over a ground plane, which is resonant
at two distinct frequencies. I have measured the input reflection over
frequency and the resonance frequencies are close to what they should be, if
I allow some minor changes because of the `echoic' environment where the
measurements have taken place.

Now I would like to analyse the antenna using NEC. Before I start this
analysis I have taken the measures of this antenna. Since the operating
frequencies are around 120 and 400 MHz, the dimensions of the antenna are
all small in terms of the wavelength.

Basically the antenna consists of a groundplane, a helical-like structure
and a straight wire. The geometrical properties of the helical part are such
that I am reluctant to say that it is a 'real' helical. I would rather say
it is a coil.... The straigth wire is the simple part. Finaly some numerical
data:
groud plane 80x60mm^2, helical outer diameter 7mm, length 80mm, straight
wire length 130mm.

I wonder whether there is anybody out there that has (tried to) analyse(d)
ths kind of antenna. Any info is appreciated.

Kind regards,

Gerry.

----------------------------------------------------------------------------
dr. Gerry van Dooren
European Space Agency ESTEC http://www.estec.esa.nl
PO Box 299
2200 AG Noordwijk
The Netherlands
tel: +31-71-565-4664
fax: +31-71-565-4999
e-mail: gerry_at_xe.estec.esa.nl
Received on Fri Nov 22 1996 - 15:44:00 EST