"Cecil Moore" wrote in message
...
Roy Lewallen wrote:
Most of the available implementations of NEC-2 include the ability to
generate a helix. Look for information on a 'GH' command.

Some time ago, I generated an 8-sided coil for EZNEC 2.0. It was a
lot easier than I thought at first. Here's one turn of dia=13" at
about one turn per inch. Note 'y' always equals the x value from two
lines up.

x y z
.5, .2, 4.00
.2, .5, 4.01
-.2, .5, 4.02
-.5, .2, 4.03
-.5, -.2, 4.04
-.2, -.5, 4.05
.2, -.5, 4.06
.5, -.2, 4.07

--
73, Cecil http://www.qsl.net/w5dxp

Your helix is far more elegant than my octagonal structure, where each turn
is in the same plane, and a 90 deg segment then connects to the next turn.

I have just experimented with the GH card -- combined with the GM card. It
appears to be an excellent method of constructing a helix. I have not
seriously attempted to determine the optimal segmentation, but as long as
the segments are less than or equal to the turn spacing the results seem
acceptable -- as with parallel transmission line models. I have also
attempted to maintain the same segmentation on wires external to the helix,
and to use the same wire size. While these structures are interesting, from
the point of view of analyzing current distribution on an antenna, there
seems to be very little difference in the actual performance of an antenna
modeled with lumped element components. What I have learned (as mentioned
in a previous posting) is that it is possible to predict, with a fair degree
of accuracy, the actual inductance of a helix.

73,

Frank