6 Meter / 2 Meter / 440
Tri-Band Sleeved Collinear
W7LPN Rick Frazier
Here is a Tri-Band
6/2/440 Collinear antenna that if built properly, using the materials
suggested by the author, should give you years of service.
It is a
heavy duty fiberglass radome style collinear multiband vertical
capable of operating on your choice of 6 meters, 2 meters or the 440 ham
band. The radome enclosure is about 18 feet
long containing the 5 antenna elements. Mother Nature will need lots
of help to harm it!
PREPARATION FOR BUILDING
Fiberglass Tubing from
Max-Gain - 4 sections:
1ea 1 3/4" X 48"
3 ea 2" X
(Only 2 of the 3ea 2" X 48" sections are used for the antenna.
I used the extra 2" section for later on the bottom
Tip: PVC CAN BE
SUBSTITUTED for fiber glass tubing, but won't be as
Galvanized Hardware cloth 1/4" or smaller mesh at any
3 sections 38.1/4" X
2 sections 19.1/8" X
20 feet. #18 insulated wire (used for hookup of elements from
bottom to top)
Wooden Dowels- 5 pieces 1 1/4" x 6".
for support of antenna elements inside radome and to center connecting
Hot Glue gun
tools as needed
Drill 5 pieces with 8" x 1/4"
drill bit and drill press.
Tip: If you don't
have a drill press, just use a 4 inch or longer 1/4" drill bit.
the dowel in a vice upright and drill as carefully as possible starting
centered at one end of a dowel and drill towards the center of the
opposite end. Repeat from the other end. Hopefully the holes will meet and
you will have a 1/4 inch hole all the way through the dowels. Smaller or
larger size drill bits may be used as long as #18 wire will go through the
hole in the dowel easily.
Drill center of dowel end to end as best
possible. If you are a perfectionist, just take the dowels to a local shop
that has a drill press and tell them exactly what you
Next, near the center of the dowels on opposite sides, drill
45 degree angle holes down into the center hole. Both holes should exit
the dowel near the center 180 degrees apart, (on opposite sides). This is
required so you can pull the #18 insulated wire through the dowels so it
can be fed to the next element. See Drawing
Preparing the coax
5 ft RG-213 with high quality PL-259 at one end. Strip
about 3 inches of insulation back and twist the shielding together so both
conductors may be pulled through the bottom dowel later. The bottom dowel
must be drilled large enough so the coax can be pushed through it. Leave
about ¼ inch inner insulation on the center conductor to isolate them
7 pieces of #43 ferrite beads for
balun. You must slide them over coax now before assembly of antenna
unless you leave the PL-259 off until later. http://www.amidoncorp.com/
THE BASIC CONSTRUCTION:
The basic construction of
the Tri-Band Collinear consists of an outer radome of 1 3/4" and a 2"
fiberglass tubing (PVC can be used) with a PVC cap at the top. I purchased
the tubing from Max-Gain, and had them cut to 48" for shipping. The exact
length of sections or placement of the joints in the fiber glass radome is
not critical, as long as you end up with enough total length to house the
entire assembled internal parts. It will be about 18 feet including
To assemble, join the 1
3/4"X48" sections with marine epoxy and 2" X 12
sleeve tubing epoxyed
over the joints to reinforce and strengthen it. Total finished length is
about 18 feet. Refer to diagram drawing below and pictures at bottom or
Notice in the inset
in drawing that the center conductor from coax is connected to
the bottom of element #2. The shield is connected to
the bottom decoupling sleeve shown in gray in the drawing and also to
the length of #18 wire that is fed up
through the dowel in the bottom of element #2.
Building the antenna
The actual antenna consist of 1/4" hardware
cloth sections cut 38 1/4"x 4" and curled around 1"x 6" wooden dowels
placed between each element. There should be a dowel inserted in each end
of the mesh sections when done. The top and bottom sections are 19 1/8
inches long. The other 3 remaining elements are each 38 1/4 inches
If you have a long enough working
area lay out all the mesh on the floor end to end starting with a 19 1/8"
section and ending with a 19 1/8" section.
- 19 1/8" (At bottom of antenna)
#2 - 38 1/4"
#3 - 38 1/4"
#5 - 19 1/8" (At top of antenna)
1/2" space between each
Place the finished dowels between each element and at
First staple the mesh on the ends to each dowel making one
continuous piece, leaving an electrical separation between elements of
Curl them around the dowels at the ends of the 38
1/4" lengths by wrapping the 4" around the dowels to form a 1 1/4" mesh
and wooden tube.
The center edges of mesh between the dowels will be
opened a little. Don't worry about that, but make sure the sharp edges are
bent inward slightly. Staying open helps keep it flexible while inserting
it into the tubing later.
The dowels have been center drilled end to
end to run the thin #18 wire through. It doesn't have to be perfect. This
allows you to maintain the thin wire #18 centered. Think of the thin wire
as the center conductor of a piece of coax and the mess as the
The thin #18 wire is threaded through the dowels and
soldered alternately, skipping one element at a time and soldered 180
degrees from the other thin wire connection to separate the connections
electrically. See drawing Figure 1. and Figure 2.
Element#1 drops down
over the open end of the coax as a decoupling sleeve with dowel #1 drilled
1/2" so it slides over the coax.
Solder the shielding to the upper
end of element #1 on the opposite side where you will solder the center
conductor to element #2. At that same spot, a thin #18 wire is
soldered to the shield and threaded through dowel #2, between
elements 1 & 2, up through dowel #2 to element #3, which is repeated
to #5. 45 degree holes in the dowels are there to pull the shielding
downward, and the center conductor up and
center conductor of the coax is soldered directly to element # 2, then a
thin wire from the top of element #2 threaded though dowel (#3) up and
through dowel (#4) and soldered to element #4. Then, the #1 shielding
decoupling element (at bottom) conducts to #3, which conducts to #5. #2
center lead conducts to #4.
In other words, the center
conductor of the coax feed, using #18 wire, is connected to
elements 2 and 4 ONLY. The shield of the coax connects ONLY to elements 1,
3, and 5, using #18 wire.
If you are having trouble understanding this,
just refer to the drawings.
The finished internal parts are
close to 13 feet minus the balun.
I chose to use the other 48"X 2"
fiberglass tubing as a bottom mounting stub and to cover the balun for
weather proofing. I slid the 2" tubing up over the 1 3/4" tubing, 2
feet, to reinforce the base and leave enough to cover the balun.
Balun is provided by placing 7 pieces of #43 ferrite beads at 38" below #1
We used spray silicone to
slide the completed "guts" into the radome and held everything in place
with marine epoxy.
Everything is sealed air-tight within the fiberglass
some un-scientific "gain" and SWR
2m - 8.56 dBi
440 - 12.02
6m - 3.07 dBi
from the idiot meter on my FT-857D
Barely shows a mark from 144.1
to 147.9 -1.2 or better.
about 1.4 to 1 for the entire 440
6m - Still checking. Seems about 1.7-1.9 to 1.
Im going to get a good SWR
Caution! It is suggested that no more than
100 watts of power be used with this antenna on any band. Higher
levels may damage the antenna or your transmitter! Exact safe power levels have not been
If you are familiar with the
(http://www.sadona.com/news/ant_coaxcol.html) made from RG-58 of similar length elements,
all I have done here is used large elements for broader band width and
removed the velocity factor shortening of the coax, borrowed the
thin wire alternating with large diameter elements from the
(http://home.comcast.net/~ross_anderson/sc.htm), and beefed up the wind loading.
Practical reception should be better due to the increased overall length.
This is a very strong antenna. We have joked about mounting an American
Flag on it.
rickenbrook at clearwire.net