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THE DOUBLE BAZOOKA
ANTENNA
About The Double Bazooka Antenna
The Double Bazooka Dipole is a very efficient single band antenna which is very quiet, and does not require the use of a balun. This antenna consists of coax (RG58) or other 50 ohm type with the shield split at the center and the feedline attached to the open ends. Do not break the center conductor. With the feedline attached directly to the two open ends this acts as a half wave dipole along with the open wire end sections. This double bazooka can be cut for any operating frequency and is broad banded. It can be mounted as a flat top or an inverted vee and will handle the legal limit. As an added plus, it can be operated as a multiband antenna by using a suitable tuner. As with most antenna projects, get the double bazooka up as high as possible. Some tuning of the length for best swr may be required and you can use materials that are easily obtainable.
Experiment!
Additional construction
information:
(This tip from Jay, W5IB)
On the cable ends you do not
need to use twin lead. You can make these antennas using a single piece of
12 gauge copper wire or larger for each end or you can also use ladder
line etc.
I would advise using heavy end wires
for strength purposes. The weakest part of this antenna is at the junction
of the coax and the end wire or twinlead. To prevent the joints from
breaking especially for long lengths, I picked up some 1/2 inch PVC pipe.
I cut the PVC in half length wize so it would overlap a few inches on
the joints.
Place the PVC at the joints in "splint fashion" and secure
with regular screw hose clamps. Put the clamps close to the ends of the
"splint", tighten snugly and it should take the strain off the joint and
should give a strong joint.
Do this at the center using a " T "
support from PVC or use your own engineering. When designed for the lower
hf bands, this antenna can be a bit heavy since coax is used. It can be
supported along it's entire length with non-conductive cord, rope, cable,
etc by suspending and attaching the antenna from the support cable with
nylon wire ties every few feet.
This relieves the tension and strain
from the center and end
connections.
-----------------------------------------------
Additional
info and updates from builder Steve,
K4MMG
I used RG58 to
build the Bazooka using the plans and formulas above...
The antenna
height is 30 ft., the ends are @ 10 feet.
( I let there be a lot of
slack in both ends ) .
I used 11 feet of heavy wire on the ends rather
than twinlead.
This is to prevent the coax from being pulled on
unnecessarily during windy days.
The coax feed line is 60 feet in
length and is rg8x.
Using a MFJ
analyzer I obtained the following results:
7.1 Mhz = 60 ohms @1.4
vswr
7.2 Mhz = 48
ohms @1.2
vswr
7.3 Mhz = 45
ohms @1.4
vswr
The calculated
lengths were made @ 7.2 Mhz. The tails lengths were increased from the
calculated values by 11 inches for adjustments as necessary. From the
formula in the article, (ABOVE), the antenna that I constructed without
adjustment was useable.
First time since I became a ham did
this ever happen. Even though my radio has a tuner, my goal is not to use
it. This antenna is no exception.
The antenna that
I ended with seems to be a lot more directional that the standard dipole.
That is, when the signals are at the antenna ends, they are hardly
readable.
With my all band dipole however, I can at least hear signals
reasonably well.
Signals front to back of the antenna are very strong
and I was really pleased with the results. Noise levels are very low
on receive. As it turns out because of the manner in which my antenna is
deployed, (more or less inverted V),it is probably both a vertical and
horizontal radiator.
Because the
broadcast stations are no longer in the lower end of 40 Mtr. Phone,
7.125mhz - 7.200mhz, it allows for a more enjoyable operating
experience now.
In the past few days, I have heard , JA’s, EA’s,
and Europe @ 56 levels.
I will use this antenna for a few months, then build one from rg8x coax so I can use greater than 100 watts.
Additional info......I couldn’t stand it any longer!
Raised the end to be in line with the center height, no change in swr!
Just thought u may want to add this into the post.
73’sSteve/k4mmg
(See his other projects on the Antenna Projects page)
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