After reading ON4UN's book, looking at W8JI's web pages, and using
EZNEC, one can demonstrate that an array of 8 phased verticals in a
broadside/end-fire arrangement would have greater directivity than a
broadside pair of 2 wavelength Beverages with wide spacing. To be
more specific, from page 7-83 of the fourth edition of ON4UN's Low
Band DXing, a broadside pair of 300 meter Beverages spaced 90 meters
would have a relative directivity (RDF) of 14.2 db.
Assume 23 foot tall verticals with 4 23 foot top hat wires, loaded with
30 uH and 72 ohms (derived from W8JI-style element described on page
7-18 of ON4UN's book). Modeling an 8 element broadside/end fire array
of these verticals with end-fire pairs 70 feet apart and broadside
elements 320 feet apart gives 15.5 db RDF. I'll email the .EZ file if
anyone
wants it.
Look at page 7-22 of ON4UN's book for a very similar example.
Since the Beverage array requires more real-estate (300 by 90 meter
rectangle) than the phased vertical array (300 x 22 meter rectangle,
not counting radials) and has less directivity, why don't we see more
(any) of the phased arrays? Has anyone built one? Maybe the phased
array is just so much more complex for a slight increase in
directivity.
I'd like to build one because my highly rectangular (1300 feet x 500
feet) property is "broadside" to Europe. The phased array fits,
whereas the broadside Beverage array does not. Maybe I should just
work more South Americans.
Vic, K1LT
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