[TowerTalk] Horizontal phased arrays

[L. B. Cebik]

Thanks to the kindness of Siegfried Rambaum, KB2YVC/DE8FGO, I have finally
acquired enough data on the HB9CV phased array to do an initial evaluation
of its potential.

The HB9CV 2-element array is a variant on the ZL-Special that provides
reasonably high feedpoint impedances through the use of a T or gamma match
with single (not folded) dipole elements.  When designed for a compromise
between gain and f-b (rather than using max f-b as a sign of perfect
phasing), users claim the antenna equals or exceeds 3-element Yagi
performance.

The notes at my site start by exploring what standard we should use for
3-element Yagi performance, along with maximum 2-element Yagi performance.
The HB9CV, with dimensional formulas from a standard German Antennenbuch
are presented, with some tentative modeling (although the complete
assembly exceeds the limitations of all the programs) of performance
limits.  Then, just for fun, there is an alternative phased array that
I generated that gives full coverage of 28-29 MHz with 50 ohms feed Z and
performance as good or better than the HB9CV without the need for Tees or
gammas.  However, it does need some series capacitance and uses elements
about 0.7 wl long.  You can get a max gain of over 7.7 dBi free space,
about 1/2 dB lower than a quite good 3-element Yagi and over a dB greater
than a typical 2-element reflector-driven-element Yagi at their design
centers.  However, centering the antenna at a gain of about 7.1 or 7.2 dBi
free space gives the best compromise between gain and f-b, while allowing
a wide band 50-ohm feed.

Since most folks think of 1/2 wl as some kind of magic, I doubt anyone
will build the alternative phased array, but it makes an interesting
counterpoint to the HB9CV, which more US hams ought to at least know
about.  If I figure out ways to more reliably model all the versions of
the HB9CV, I'll amend the notes accordingly.  My thanks to Siegfried for
sending me the extensive information on the antenna.

Hope the notes prove useful--or at least interesting.

-73-

LB, W4RNL


L. B. Cebik, W4RNL         /\  /\     *   /  /    /    (Off)(423) 974-7215
1434 High Mesa Drive      /  \/  \/\     ----/\---     (Hm) (423) 938-6335
Knoxville, Tennessee     /\   \   \ \   /  / || /      (FAX)(423) 974-3509
37938-4443     USA      /  \   \   \ \       ||              cebik@utk.edu
         URL:  http://funnelweb.utcc.utk.edu/~cebik/radio.html




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