W7LPN 2m/440 vertical
The project below is my own design for a
dualband vertical dipole for 2 meters and 440.
It requires a balun and
works very well. I like to tinker, so when I finish one project, I go on
to another, even if it works
several methods of constructing a vertical dualband dipole and a simple
method is shown first below. Note that you do not have to follow either of
the methods below exactly. You may choose your own method of construction
and mounting, materials, etc.
VERTICAL DIPOLE (The simple method....coax
VERTICAL DIPOLE (Alternate matching method below)
(Alternate method above showing 5 inch hairpin
Copper tubing 1/2" X 48" precut piece w/2 end
striped same O.D. As copper
Boom= PVC "T"s
and 1/4 wavelength tubing
One "T" must
be 1 1/4 " with 2 hose clamps to mount to Mast
NOTE: The "T"
on the Mast end and the boom must match with the same inside diameter
(I.D.) as well as matching the "T" holding the copper elements. The boom
or cross arm must go inside each "T".
Plumbing store clerks are often
intrigued about what you're building and don't mind helping you match
BUILD A DUAL BAND VERTICAL DIPOLE?
method in the picture above is accomplished by surface mounting the coax
to the PVC which should be one of the more simple methods and the picture
should be simple enough for most to understand without major
Some of the
construction methods within this article pertain to both the simple
version and the more complicated method.
The more complicated
more difficult method, is to run the coax inside the PVC cross arm
starting at the point where the antenna is mounted to the support
Using this method still leaves us with the mounting and
support of the balun near the feed point situation. The simple method
suggested first above may be the best for most builders of the vertical
dipole for 2 and 440. Use your imagination and experience with various
building techniques and experiment!
instructions below are for the more difficult method but will hide the
coax at the cross arm and will cover and seal the feed point
With whatever method of construction you choise, it is
suggested that all feedpoint connections be sealed from the
the 1/4 wave cross arm PVC, drill holes to accept coax near each
leaving enough room on one end for 5 or 6 wraps of the balun near
the center insulator T, then drill one more hole in the cross arm
(boom) near the end of the balun NEXT TO the final location of the
center T insulator for the coax to be fed into the center insulator. See
During the procedure above, pull enough coax
out to form the balun while leaving enough to work with to make the
feed connections and wrap the balun around the PVC near the end of
the cross arm and back inside the PVC cross arm then secure both ends
of the wrapped balun with zip ties or hot glue to the cross arm so
the balun will not spread apart or move in the wind.
& cap copper, 20" for each half of dipole. This length works well
on both bands.
Split 1 1/4" PVC -T lenghtwise to slide over
support mast. (See mounting to mast below)
Trim coax end & solder
connectors on each conductor of coax
Slide copper element ends into
center insulator T and screw coax leads to copper antenna
Secure with solder and then make certain ends of elements
are not touching and position the elements inside center T of
sure of connection and position of elements inside T, fill T 3/4 full
with hot glue.
I feel very strongly about the "T" center insulator
piece being sealed inside with hot glue, out of the weather and secured
where the leads cannot get yanked out or wet and corroded. I hate
water inside and it's effects on antenna joints and connectors.
time should be taken to do this on either
Don't get hot glue on surfaces of PVC to be
Epoxy T's in place ensuring vertical orientation.
clamp to Mast at top and bottom using split T and hose clamps. Again, see
mounting to mast section below for details.
YES! I believe in
keeping it easy, but I found placing the coax inside the PVC to be
surprisingly simple, clean and professional looking, water-tight, and
smooth externally, as to not catch on anything. I am fairly good
with my hands but for those of you with large hands or fingers, you may
find it difficult to build the version with the coax inside the
Securing the balun - I like hot glue. It's
cheap, water proof, and the stuff stays where you put it. If you
glue it before you're sure, it's a mess and won't come off. If you
might have to tune or adjust something, don't use hot glue until it's
tested and you're sure of the final position, length, etc. You can
use the zip ties, string or other methods to hold the balun in place
during testing. Put a little hot glue in the drill holes as well. I
like the clean looks of none or little coax showing
MOUNTING TO MAST
The split "T" which mounts to the
Mast is cut lengthwise, making two cuts 1/4" apart to remove
some PVC material in order to be able to "squeeze" it with the hose clamps
wrapped around the "T" and mast. Without material removed in the cutting
process above, the edges hit and it wont make a tight enough contact with
the 1 1/4" T.V. mast. Obviously I left the coax connectors off until the
antenna was finished.