"Peter O. Brackett" wrote in message
m...
Group:

The celebrated Numerical Electromagnetic Code (NEC) developed largely at
US taxpayer expense (Let's all Salute the US Taxpayers!) and generally
released to the public for free provides algorithms for numerically
integrating Maxwell's celebrated partial differential equations and so
enables one to obtain numerical solutions to real practical problems such
as the antenna field strengths at points in space due to modelled
practical transmitting antennas.

NEC codes are available for downloading from public WWW sites. The raw
NEC codes however do not have modern GUI based interfaces are required to
be 'driven' by Fortran style card decks and profide outputs as files and
not in graphical form.

Several enterprising folks/companies have added GUE capability including
data visualization to enable a more user friendly interaction with the NEC
codes.

For example Roy Lewallen's (W7EL) famous EZNEC programs are one example of
the widespread use of the public NEC codes that have been 'enhanced' by
Roy to provide user friendly graphical (GUI) based input/output (I/O).

Apparently the outputs from the 'raw' NEC codes provide field strengths
only in rectangular co-ordinates and so... one cannot directly obtain
readouts of the circular components for circularly polarized antennas.

Thus it is relatively difficult for non-experts to print out or to plot
field strengths in terms of right hand or left hand circular propagation
co-ordinates. For example if one attempts to model a circularly polarized
antenna such as an axial mode helix, NEC (EZNEC) certainly allows the
modelling to occur by breaking the helix into small segments that
approximate a real helix to whatever degree of accuracy is required. The
difficulty comes when one attempts to plot or graph the circularily
polarized fields resulting from the modelled antenna. NEC only provides
rectangular (x-y-z) components for the fields and not direct circular
components for the fields.

It is relatively simple to calculate the circular components from NEC's
rectangular component outputs, and a simple arithmetic transformation
routine can be written to quickly and easily process the NEC outputs into
circular outputs so that one can then obtain solutions for circularily
polarized antennas expressed in terms of right and left hand circularly
polarized components.

It seems however that none of the extant GUI equipped NEC based programs
such as EZNEC have implemented this (simple) transformation.

I suppose that since the use of circularly polarized antennas is only a
very small fraction of the use of rectilinearly polarized antennas and so
the authors of NEC must have felt that their would not be much call for
those outputs. In fact the output transform from rectilinear to circular
components is trivial compared to most other aspects of NEC codes! But in
truth there is not much (commercial) call or market for the use of
circularly polarized output plots.

Question for our own Roy Lewallen W7EL... Roy do you think that there
would be much of a market for EXNEC to provide circular polarization
outputs from EZNEC, and do you have any plans to implement output plots
from EZNEC in terms of circular polarization?

I can supply you with references to the needed transformations. Just a
few lines of Fortran or Visual Basic should do it...

Just asking? [smile]

-- Pete K1PO
-- Indialantic By-the-Sea, FL


The NEC output file lists axial ratio and tilt. Nittany's NecWin Pro, and
GNEC plot these results.

73,

Frank