I don't know if John's is correct or not, but I do
know that I have never been able to find a COS length.
Since most of the time my Beverages are about 2 feet
high, with short downleads, that may be why.
As far as I could ever determine, COS lengths exist
only in computer simulations. However, is is very easy
to move the pattern nulls around. Moving a null onto
the reference signal may give the impression that the
F/B is improved.
Stagger end-fire phasing is a sure way to improve F/B
on short wires especially. Last season I had trouble
with some noise sources off the back of one of my
short Bev's. I finally gave up messing with lengths
and such. With limited space for this direction, I
spaced a second wire 8 feet away and 54 feet back.
These dimensions were determined by the space
available. In fact, I put the wires up where they fit
and then measured them. A phasing line was calculated
and crossfire phasing was used. The results were
amazing. Performance was about equal to wires almost
three times longer! Certainly optimum spacing and
stagger would have been better, but don't give up on
endfire just because you can't stagger them a quarter
wave!
73,
Larry - W7IUV
DN07dg
http://w7iuv.com
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