If there's no conductor loss in a model, and no ground loss from a
ground system (which can be simulated with a MININEC type ground), the
gain of an infinitesimally short vertical should be about 0.45 dB less
than for a quarter wave vertical. The gains for intermediate lengths
should fall between. The gain difference is caused by the change in
current distribution as the antenna length changes, which in turn causes
a slight change in the pattern shape.

If you're seeing a report of higher gain from the shorter antenna,
something's wrong. Do an Average Gain test to make sure there are no
numerical problems, and also check the segmentation to make sure it's
reasonable. And, of course, make sure that the length is the only
difference between the models.

Roy Lewallen, W7EL

John Ferrell wrote:
Showing my ignorance (or perhaps deteriorating intellect?) again:

I am attempting to compare the gain of a full size (1/4 wave) vertical
to various shorter verticals at 160 meters.

I am looking at the gain in dbi on the 2D plot. I see 1.39 dbi for the
full 1/4 wave and I see 1.52 dbi for the 28 foot version.

I don't believe the shorter antenna has less gain. Where am I going
wrong?
de W8CCW
John Ferrell W8CCW