DOUBLE BAZOOKA/COAXIAL DIPOLE ANTENNA
A typical, dipole antenna has bandwidth of about 50 to 100 KHz. The
bazooka is resonant in the center of the band and had an SWR of 2:1 or
less across the entire 80 meter band?
The "Bazooka" antenna was developed by the staff of M.I.T. for radar
use. The original "Bazooka" used coaxial cable for the entire radiating
The adaptation used in amateur radio uses coax only for
the broadbanding portion of the antenna, while the remaining
portion of the elements are constructed of twinlead or ladder
line (see attached sketch). Ladder line is preferable for its
This is a single band antenna. It will not radiate harmonics
of your operating frequency. In addition, there is very little
feedline radiation, which is great for those who have problems
with TVI. Its broadband characteristic makes it ideal for 80
meters and 10 meters.
The Bazooka antenna consists of a half-
wavelength of coaxial line with the outer conductor opened at the
center and the feedline connected to the open ends. The outside
of the coax and the ladder line operate as a half-wave dipole.
The inside of the coax elements, which do not radiate, are
quarter-wave shorted stubs which present a high resistive
impedance to the feed point at resonance. Off resonance, the
stub reactances change in such a way as to cancel the antenna
reactance, thus increasing the bandwidth of the antenna.
At the very center of the coax carefully cut away about one inch of the
outer vinyl jacket.
Then cut the exposed shield all the way around at the center of
the exposed area. Be careful that you do not cut the dielectric
material or the center conductor in the process. Twist the two
pieces of exposed shield into small pig-tails. These are the
feed-point terminals for the antenna. The center conductor of
the feedline is soldered to one and the shield of the feedline to
the other. Now solder the center conductor and shield together
at each end of the antenna element. Solder the two ladder line
wires to the end of the antenna element. At the other end of the
ladder line, solder the two wires together.
Use a square piece of plastic at the antenna center, drilling a
small hole on each side of the coax, wrapping a small wire around the
coax and through the holes and twisting the wire together on the other
side. A small amount of quick setting epoxy secures the
coax to the plastic support and prevents the wire from untwisting.
A coating of silicone rubber or epoxy seals and protects the feed-point
from the weather. Do the same where the ladder line is soldered to the
shorted end of the coax.
Short the center to shield at each end of the coax.
Short the twin lead at each end and solder the coax/shield juction
to the coax.
50 Ohm Coax feedline
at least 66 feet long.
shield side center connection side
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Twin-Lead coax Twin Lead
example: 3.888 kc
total length 118.3 feet
coax length 83.6 feet
twin lead length 34.7 feet