They claim to
> have improved the feed so it not only has better F/B than the normal 2 el
> beam but better gain (how does a feed system do that??) I suspect the
> improved F/B makes it appear that the antenna has more gain.
A ZL Special or HB9CV ar both variants of a phased horizntal array.
Another version is the Field Day Special, which W7EL published in QST a
number of years ago.
With proper phasing, 2 elements at about 1/8 wl spacing will yield more
f-B and a bit more gain tha the same elements when set for the best F-B
that parasitical operation will allow. The same elements can be set for
more gain parasitical, but the F-B goes to pot. Phasing allows on to find
an intermediate setting that gives about 20 dB F-B with about 6.5 dBi
free space gain. A normal 2-el setting parasitical would give about 6.2
dBi gain with about 11 dB F-B.
The phasing system can be set for max F-B (a rear dimple about 50 dB
deep), but at that setting, the gain goes to about 6 dBi. One can also
set it for max gain (a bit over 7 dBi), but with about 7-8 dB F-B or
less--the same as a max gain parasitical setting.
Not all combinations of element lengths and available feedlines pressed
into phase line duty will yield a successful phased array. Since a
phasing system is designed to provide the rear element with the correct
current magnitude and phasing relative to the forward element for a given
spacing and set of element lengths--for a desired set of operating
characteristics, design can be tricky. There are some notes on the HB9CV
at my site.
-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://web.utk.edu/~cebik/radio.html
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