You've never heard of a Double Bazooka
antenna? I'm not surprised. The Double Bazooka had its origin in the 1940's as a
broad-band, half-wave antenna for use in radar installations. It subsequently was
introduced in the amateur community in the 1950s.
The antenna never gained widespread use in the amateur world because of difficulties in
construction. Rarely could an amateur build a Double Bazooka that could and would
withstand the harsh wind and ice loading that we encounter in our everyday environments. I
believe that the construction problem has been solved in this antenna.
The antenna construction begins with a length of 50 ohm coax. The shield is split in
the middle, but the center conductor and its insulation are left intact. The shield
becomes the radiating element of the dipole. The 50 ohm feed line is attached to the
center braid of the coax through a proprietary design connector. This connector has an eye
hook for mounting the antenna in an inverted-Vee configuration. It also has an SO-239 coax
connector and the entire center connector is enclosed in high-shear, UV-resistant potting
compound.
At the ends of the coax, the center conductor is shortened to the braid, and this end
is extended through industrial-grade 300 ohm twin lead. The coax is bonded to the
twin lead with mil-spec heat-shrink tubing. This assembly technique ensures a high-strength,
UV-resistant antenna.
The antenna has no exposed metal wire. This feature should reduce static buildup on the
antenna. Those of you who have antennas that suffer from rain and snow static can
appreciate this advantage.
The antenna will handle the full legal limit. The company recommends that the antenna
be mounted in an inverted-Vee configuration. I have tested the antenna in the inverted-Vee
and horizontal configurations. Measurements were made using an MFJ 259 SWR analyzer at the
end of approximately 90 feet of RG8x coax. |
I first installed the antenna as a horizontal dipole at a
height of about 55 feet.
This is how the antenna looks when you take it out of the box prior
to putting it up.
The SWR was 1.4 to 1 at resonance, and it rose to about 1.6 to 1 at the band edges. I
next installed the antenna as an inverted Vee (the recommended installation) with the
center at about 35 feet. With this installation the SWR was 1 to 1 at resonance and about
1.4 to 1 at the band edges. In either case, the antenna produced many solid contacts even
when I was running QRP.
For those of you who may want more gain from your antenna system, the company offers an
option for phasing two of these antennas. They predict a forward gain of approximately 5.5
dB and a front-to-back ratio of about 20 dB.
The company offers antennas for 17, 20, 40, and 80 meters. The price of the 40 meter
antenna is $115. For more information, contact International Antenna Corporation, P.O. Box
121430, Clermont, FL 34712 USA
(407-380-6270).
Fig. 1 The basic configuration of a broad-band dipole, once commonly
called a "double bazooka." The original antenna used open wire or ladder line at
the ends. In the International Antenna Corp. version the ladder line has been replaced
with an industrial-grade 300 ohm twin lead. This increases the bandwidth on 80 and 160
meters and at the same time increased mechanical strength.
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International Antenna
Company