Print Instructions for this J-Pole
Copper Cactus Dual-Band Super J-Pole Antenna Project
Your going to like this super J-pole project, This home made j-pole is easy to build
and sturdy, While looking for an jpole antenna project to build I remembered seeing a
Marine antenna called the Super J-Pole in the 1988 ARRL Antenna Handbook,
which claimed a 6 db gain over a quarter wave ground plane. I didn’t
have a machine shop at my disposal to fabricate the parts shown in the
Marine antenna article so I set about redesigning the antenna using
materials that were easy to find and work with. I have had very good
results working with copper J-Poles, so I built my refined version of the
classic J-Pole. I then added a short insulated section, the extra half
wave of vertical length, and the needed half-wave matching stub.
Here is a schematic drawing of the home brew J-pole
All the materials except the S0239 fitting can be found at
any good hardware store, and the whole antenna can be made in less than an
In my design I use 1/2" copper schedule M tubing and
1/4" soft copper tubing. I had experimented with using Teflon
insulator, but have since changed my design to use a 9" length of
hardwood dowel with three coats of lacquer as the insulator, for more
Clean all the tubing, and then from the 1/2" tubing
cut one piece each of the following lengths: 57-1/2"; 38";
19"; 2", and a piece about 3" long for a stub to mount the
antenna. In addition to the tubing, buy a 1/2" elbow, a 1/2"
Tee, two 1/2" end caps a 1/2" threaded fitting, and a cast iron
floor flange for mounting. Get a piece of 3/16" or 1/4" soft
copper tubing 42" long. Find the center of the 1/4" tubing and
bend it around a 1"-to-1-1/4" diameter water pipe or dowel.
Put the Heat to it
Now fire up the torch and start the assembly process from
the bottom. See Figure 1. Use flux on all joints, solder the 1/2"
threaded fitting to the mounting stub, and solder the 1/2" Tee
fitting. Then proceed with the 57-1/2" section, 2" cross piece,
and 19" section. Pay close attention to getting the 19" piece
parallel to the 57-1/2" piece. After these have cooled, drill through
both the 57-1/2" section of the 1/2" tubing and the hardwood
dowel about 1/4" from the top end of the 1/2" tubing, and the
bottom of the 38" section of the tubing. (See Photo A.) Then insert
the 1/4" tubing to the 1/2" tubing and sweat solder the end
caps. After these have cooled, clean the entire antenna, bend the half
wave matching section to a half circle of about 4" radius around the
antenna to help the balance and match.
Simplify the Feed Point of the J-pole
The feed point also needed to be made simpler, so I elongated one of
the mounting holes of a panel mount SO-239 fitting and inserted a
stainless steel adjustable band clamp. This goes on the 57 1/2" long
section of 1/2" tubing. A short 2-3/4" length of # 14 copper
stranded wire is soldered to the center terminal to go over to the
19" section. I used another stainless clamp to attach this. (See
Photo B.) While experimenting to find the proper feed point, I found that
the distance above the crossbar should be about 3".
1 10-foot section of schedule M 1/2" copper tubing
1 1/2" copper elbow
1/2" copper Tee fitting
2 1/2" copper end caps
1/2" copper threaded fitting (for mounting)
1 1/2" cast floor flange (for mounting)
1 Piece of 3/16" or 1/4" soft copper tubing 42" long
1 Piece of 1/2" hardwood dowel of Fiberglas rod
1 SO-239 panel mount coaxial fitting
1 Piece of # 14 stranded copper wire
2 3/8" by 7/8" stainless band clamps
Solder and flux
A weight to keep parts aligned while soldering
Steel wool or a Scotch Brite pad (for cleaning all copper)
Spray can of clear exterior lacquer (to finish-coat completedantenna)
1. You may use a Fiberglas rod as an insulator, but you
will have to be very careful with the torch or you may weaken or burn the
rod, or make it brittle.
2. When cutting the 1/2" copper tubing, cut the
57-1/2" piece from one end of the 10" length, and the 38"
piece from the other end. By doing this you will have factory-cut edges
for inserting the 1/2" dowel.
3. Be sure to keep the flame of the torch away from the
insulator to avoid burning it.
4. Use paste flux on all joints when fitting the pieces
together. Use enough flux, since you will be cleaning the entire antenna
with solvent after assembly.
5. Use a weight to hold the 19", 57-1/2", and
2" pieces, and the Tee and the elbow, flat when they are sweat
6. Use a ruler or caliper to check the spacing between the
19" and 57-1/2" pieces, to keep them parallel to each other.
7. When drilling the SO-239 fitting, use the drill press.
Be careful not to drill into the threads of the fitting. After the holes
are drilled, file the opening flat for a better band clamp fit.
8. After the best match has been found, you may want to
solder the SO-239 and the stranded wire end to the 1/2" tubing.
9. When the antenna has been cleaned and matched, spray
the entire antenna with a coat or two of clear lacquer to keep it looking
10. After everything else has been done, apply silicon or
a butyl rubber compound to the insulating section, then cover the joint
with electrician's tape for a weather tight seal.
11. A 1/2" pipe coupling and a length of pipe may be
used in place of floor flange for mounting in a roof tripod.
|First Name: Allen
Call Sign: n0sck
Comments: I built the Copper Cactus Dual-Band Super J-Pole in 1992, twice. The first used the dowel, the second I used a PVC 1/2 inch female coupler and two threaded copper male adapters. I shortened the upper and lower elements by the amount the adapters added. I also drilled and tapped one of the flats of each adapter and used 1/4 inch compression to 1/8th inch male pipe adapters for the matching stub, again reducing the length by the appropriate amount. I also fashioned a mount for the SO-239 by splitting a 2 inch lenght of 1/2 inch copper lengthwise and flattening out 1 half while leaving the other half alone. During tuning I simply clamped this to the pole, after I found the perfect spot I soldered it in place. ( See Picture )
This antenna has been up and in continuous use since 1992, It has never needed retuned (I use a MFJ 269 analyzer to check periodically. The winds in Kansas do blow and this is the only antenna that I have that has not needed repaired!
| Suggestion by KB9TIO
An Improved(?) feed arrangement is to use copper couplings,
same size as the tubing. Split the coupling lengthwise, bend out
@ 1/4" and notch for the so-239 inner ring. attach with sheet
metal screws an/or solder so-239 to coupling. repeat with 2nd coupling
and solder other end of #14 wire to flat on coupling. this provides
a strong joint and very easy tuning by sliding the couplings up
or down the tubing as needed. this tip was given to me by Tom-KB9OZZ
Thanks, Matt KB9TIO
Suggestion by KD7GQC
I have also seen variations on the J Pole which omit the insulator
section. In the first, the center conductor is soldered directly
to the driver element, and the entire antenna is thus at DC ground.
The second variation is also an all-copper design, but you capacitively
couple the RF to the element, by wrapping several turns of insulated
wire from the center conductor around the driver section of the
J pole. I can't vouch for the second approach, but the first seems
to work great, for installations where a DC short to earth is not
a problem. It seems to me that eliminating the insulator section
makes for a simpler, and potentially stronger, design. Kudos on
a great antenna! 73s, Brian KD7GQC
I made one of your "J-Pole" antenna's with some mods. I cut 2 pieces of 1/2 tubing about 11/4" long and split them. I cut a 1/4' tab in the center of each, mounted my SO-239 to one and drilled a hole in the other for soldering the wire in. I used #10 solid copper wire for the center of the SO-239 to the short length of the "J". I used two 7/8" stainless steel hose clamps to hold each piece in place. I also used a full 3 foot length of 1/2" dowel rod to join the two longest pieces together. I drilled three holes thru the copper and dowel on each long piece of copper and used 7/8" 6-32 screws and nuts for each. This seems to add a great deal of support for the two.
KC5RFL has an antenna analyzer and he checked my SWR's. Came out 1.1:1 at 146.610mhz. Great.
|Call Sign wb5hds
Country: United States
Comments: Iv'e used 10ft sticks of 1/2" galvanized 'emt' conduit to build my j-poles. i drill a 1/4" hole where the "j" goes on and use a piece of 1/4" copper and solder it in place, then attach the feed line. less than $6 invested using new parts. if you want a "super j", then use a piece of 3/4" pvc as an insulator and add your stub and pole, still very cheap. can't tell ANY difference in preformance. we hams have fun don't we....Dave
Call Sign N3TZO
Country: United States
Comments: The antenna is up, and performing with nice results! All connections are soldered, and I decided to paint mine white (except for the match, which I shined and laquered because it just looks cool). No more than 1.5:1 SWR at any point, and getting positive feedback on my signal. Thanks for the design info, and help.
One last suggestion:
put a piece of steel about 1/2 or 3/8 of about a foot and a half
up the center of it ( from the base ) this will strength the bottom
portion of the pole.. put a small curve in it so it touches the
inner wall of the pipe.. my parents use this j-pole and live in
a windy area.. and this fixed that problem.
In order for these instructions
to work great.. Please send me feedback on if you had problems and
what can be done to help the next ham.. I don't get much feedback
on the copper cactus J-pole, Guess that's good in a way, but would
love to either way Praise or
Suggestions about this project.
Print Instructions for this J-Pole
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