On 3 Dec 2006 07:54:37 -0800, "N4aeq" wrote:

First off if size is no problem then what would be the advantage to
two stacked yagis opposed to one long yagi, considering the gain of
each setup would be equal?

Depends to some extent on whether you are focussed on gain in the
desired direction, or rejection of unwanted signals, or a balanced
system assessment (eg G/T).

Stacking a pair yagis in one plane narrows the beamwidth in the
orthogonal plane... so if you stack two horizontal yagis above each
other, you achieve the gain increase by reducing the vertical
beamwidth without much change to the horizontal beamwidth or pattern.
The stacking distance influences the pattern, the location of the
pattern nulls near the main lobe, the magnitude of side lobes.

Obviously there are a bunch of mechanical / physical issues depending
on the required gain, and the stacked yagis requires a more
complicated feed arrangement which has additional loss which might be
significant if you were chasing best G/T ratio.

Owen
--