Is there an EZNEC guru in the house?

[Iain McFadyen]

Hi Tacoistas!

I'm sure a lot of you are 'making a list,... checking it twice' as you pack
everything in your cars and head to your nearest Field Day location for
some weekend fun....

... but if not, is anyone a wizard with the full version of EZNEC? My demo
version doesn't allow me to do the experiment I want...

The basis of the investigation is to start with a standard yagi, on any
band you like. 144, 430, 2400 MHz... anywhere. Nominal number of directors
(5-10 for example), and a single reflector.

Result should be a nice radiation pattern, with the main lobe right down
the boresight of the antenna.

Experiment 1. Lose HALF (i.e. one side) of the reflector. Does this affect
the direction of the main lobe? Does this pull the lobe slightly left or
right of boresight? By how much?

Experiment 2. Restore the correct length reflector, but now offset the
reflector by a few percent, left or right. So it is the right length but
not properly centred. How does this affect the skew between boresight and
direction of maximum gain?

What I am looking for is a small but definite (maybe 1 or 2 degrees)
skewing of the main lobe away from the boresight. If the experiments to the
reflector don't do it, would the first director perform better, if the
experiments were repeated on the director?

The ultimate goal is to find a way to electrically steer the main lobe of a
yagi off the main boresight of the antenna. I was considering using PIN
diodes to electrically adjust the length of the reflector element.

Are there any existing commercial implementations of this?

Any thoughts much appreciated.

Iain   in 9Y4-land.
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