Hi Frank,
I used a pair of 270 foot spaced broadside 580 foot Beverages for several
years but the improvement was insignificant compared to a single 580 foot
Beverage. I replaced them with single 900 foot Beverages which perform
slightly better than the 580 foot Beverages. I have inadequate space for
more widely spaced broadside Beverages.
We sometimes see claims broadside spacings less than 1/2 wave result in
useful S/N or directivity improvements. They do not. Gain goes up 3 dB
(because the individual elements are so lossy), but pattern does not change
any significant amount. When pattern does not remove unwanted signal areas
significantly more, S/N cannot change significantly. We can't improve
things by nulling unwanted stuff out of an area that already has very little
response.
My results with Beverages are similar to your results. The problem with 1/2
wave spacing is it tries to force a null where the individual elements
already have a null. In order to improve weak signal performance, we have to
force new nulls where significant response exists with the basic element. We
can't make things significantly better by just adding a new null inside an
existing null, because there is already nothing of consequence there to get
rid of.
Since a 1 wave long Beverage has deep side nulls, adding a second antenna at
a spacing that forces new nulls in the area of existing nulls is a waste of
materials.
You've surely built and evaluated more BSEF and 8-circle receiving arrays
than any of the rest of us. I'm very new to them and after just a few
days of evaluation I'm delighted with the results of my new BSEF receiving
array consisting of four 25 foot W8JI umbrella verticals spaced 300 feet x
130 feet. I still have my 900 foot Beverages, but so far the performance
of my new BSEF receiving array is consistently superior.
If you were to install a new BSEF receiving array using four W8JI
inductive/resistive loaded 25 foot umbrella verticals (not an 8-circle
array) what spacings and fixed phasing would you use based on your
experience and evaluations?
I can't really give a specific answer because the optimum phase depends on
the element combination and what people are after. What is best at one place
is probably not best somewhere else, and it is the combination that matters.
The only certainty is 1/2 wave broadside and 180-s phase is almost never
optimum for anything, including transmitting.
For receiving, I would plan the phasing or spacing of directive cells so
each complementary cell forced the largest possible area null where other
cells had significant undesired response.
73 Tom
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Topband Reflector
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