Hi All,
> Two endfire Pennants will narrow the cardioid pattern only slightly. The
> TOA will also lower slightly and, of course, there will be about 3 dB
> gain over a single Pennant. There is really little advantage for the
> endfire Pennant configuration.
I respectfully disagree with Earl on this. It is like concluding making a
Yagi longer does not or cannot increase gain or directivity. Pennants,
Flags, K9AY loops, and EWE's are all really just two-element verticals with
a very broad pattern and RDF about the same as any two-element array (the
horizontal component of the wire makes them slightly less performance than a
true vertical). Like a Yagi or any other end-fire array, directivity HAS to
increase with length, and with proper phasing will be close to 3dB
improvement with a doubling of array length.
The most common problem when people try to phase arrays is picking the wrong
phase angle. Combining small array cells requires NOT placing a null where a
null already exists, otherwise you gain nothing or very little. In other
words, do NOT use conventional cardioid + cardioid phasing, or you gain very
little (except extra F/B).
If I were going to combine end-fire (in line) cells of unidirectional
(cardioid) elements, I'd use 180 degree or some other shift between the
element cells. This would force two new nulls directly off the sides and
improve directivity by removing signals from the sides. F/B would not
change, gain may not change substantially, BUT receiving ability would
improve quite a bit quite a bit because the directivity (average gain to
gain in desired direction) would improve noticeably.
(Never use gain or TOA as a measure of RX antenna performance! You want
maximum RDF, which is the difference between average gain and gain in the
desired direction and angle.)
It also could be worthwhile to use Echelon stagger with Pennant arrays (or
any other array of cells) if phasing is correct, but you would have to be
careful to select the correct phasing for maximum RDF.
By the way, be very careful considering TOA of verticals with Eznec and
other programs. The programs we commonly use calculate patterns at infinite
distance over flat earth. This causes any earth attenuation to appear as
taking FS to zero at zero elevation, when that is not true. The pattern is
not a correct representation of the true response for distance closer than
the "infinite distance" point where the model calculates pattern. For
example, we all know BC stations have considerable FS at zero degrees for
many miles, yet the model will show no groundwave!
Also, we want maximum RDF at a given angle and direction....not a certain
maximum gain at a certain elevation (TOA).
Always use RDF.
73 Tom
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