Tennadyne has modelled stacked lpda's, and offered
a few words of wisdom today.
1) you can expect 2.2dB from stacking any pair of
antennas. if you're not careful about matching the
common point impedance, you can lose 1 dB of that.
It almost doesn't pay to bother.
2) By stacking...depending on height....you will
clean up the pattern, and suppress high angle lobes.
You will also RAISE the lower lobe of the in-phase system
by a couple of degrees.
3) It was their opinion that getting a single antenna higher
would almost always be better than a stack. Until you want to use it for
sweepstakes.
4) My conclusion was that a single antenna, with the ability to
modify its height, was probably a better solution.
5) Tilting the lpda's, so as to approximate 1/2 wave spacing at all
frequencies, probably isn't worth the effort. But it bears modelling,
just as each of the other solutions and heights do.
Thanks again, for all your inputs.
Jim Jarvis
N2EA
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