It is my experience that Beverage antennas really do want to work and
are quite forgiving of imperfect construction techniques. I have never
had anything but good performance from every Beverage I have tried.
I currently have two 2-wire Beverages--one NE/SW and the other SE/NW,
each about 450-500 feet long. One Beverage is end-fed while the other
is center-fed (actually off-center somewhat). I have to admit the
construction is rather haphazard, partly because of the circumstances
of the environment. Trees are used for supports, with one wire on each
side of the tree trunks. Average wire separation is about 12 inches but
depending on the trees which are used, it varies from 6 to 24 inches. I
do try to avoid abrupt changes in wire spacing. I also try to keep both
wires side-by-side in a horizontal plane to maintain good symmetry with
respect to ground, but where only small tree trunks are available, I end
up stacking the wires vertically to maintain the separation. The 2-wire
Beverages perform every bit as well as the single-wire ones they replaced.
My ground terminations consist of 8 foot ground rods. I tried adding
radials but I could not detect or measure even the smallest change in
performance. Local ground conditions are mostly swampy. I tried using
reflection transformers at the ends of the Beverages, but this actually
produced poorer directivity than simplying grounding one wire directly
to the ground rod. My reflection transformers probably were not a good
match to the antenna but the performance is so good as is, I see no
need to try to redo the transformers.
I routinely see 20-30 dB rejection off the sides and back. For some
azimuthal and elevation angle-of-arrival conditions, the rejection is
phenomenal. Very strong S9+20 dB signals will literally disappear
when switching directions.
The one area in which I do take some care is in the feed transformers.
I use the design in W1WCR's Beverage Handbook. I have carefully pruned
each transformer to match the feedline as well as possible. This can
be done with an antenna noise bridge or even with an SWR bridge, feeding
the antenna with low power RF and adjusting for lowest SWR. It should be
possible to get nearly a 1:1 match. With proper matching, preamps should
not be necessary. Also, because there are two feeds from the 2-wire
Beverage (one for each direction), I use a relay to switch in a resistive
dummy load termination for the unused feed. I use 75-ohm CATV coax with
aluminum foil shielding for feedlines.
In short, the beauty of the Beverage is that it is so simple. There are
no critical lengths, spacings, or phasing conditions to fuss with. Of
all the directional antenna systems I have tried, the Beverage is by far
the easiest to get working. I hope these comments are helpful.
73,
John W1FV
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