On Mon, 22 Jan 2007 11:09:28 -0800, "RST Engineering"
wrote:

I tried simulating a Slim Jim in EZNEC and did NOT get the expected "aim at
the horizon" low-angle radiation simulated pattern.

Hi Jim,

This is the problem of the variability of matched, halfwave antenna
results in life too. Most antennas are connected to coax drives, and
are not excited by point sources. However, you are not asking about
the complexities of uncoupled lines even though we get their
complaints here all the time.

I got instead the
standard "hole in the donut" that you would expect from a vertical dipole
and a rather fat true donut shape rather than the expected pancake pattern.

I would argue that your expectation would defy both experience and
analysis. Of course, just what a pancake pattern means leaves open a
lot of interpretation. Myself, that would mean to me to be an
especially high gain.

One of the wild cards of analysis which can really skew the numbers is
how you choose the height above ground. The patterns tend to exhibit
a mud puddle splash achieved when you jump in with both feet.

I'm not at all sure how to connect a "voltage source" driver at the tap
point without being able to simulate the ground of that voltage source
tapped up from the bottom end as well.

I presume this tap is across the match section. Just make it a short
wire connecting to both the short element and the long element, with
the source in the middle segment of the short wire. Voltage, current,
or power source driven is not going to matter at all to the results.

73's
Richard Clark, KB7QHC