Look no further, the J-Pole is for you and is easy to build and adapt to pretty much any materials.
First off, I got my Ham licence in June of this year and had a J-Pole built right away at the advice of our Club President Bob. When asking about what would be best, he directed me to eham where someone had taken the time to write up instructions and results of his use of a J-Pole antenna.
So right away, I raced to Home Depot and bought some copper pipe, one T junction, one elbow and 2 end caps. I already had an SO-239 chassis mount connector in my parts bin and put it to good use. I also have experience with plumbing so soldering copper pipe was simple. As long as you make sure to measure exactly, you should be able to get 1:1 SWR using this antenna.
It’s currently mounted in my attic and is my main VHF antenna, it is great! I used 1⁄2 inch copper pipe for my build, but technically, you could use anything. Brass pipes? Smaller copper pipe? Ladder Line? TV Twin lead? Aluminum pipe?Yep, yep, yep, yep and yep... use your imagination! And Google away!
For example, I’m going camping this weekend, and I want to see if I can hit some repeaters from my camping location. When I shared this with Tom, he said why don’t you build a J-Pole with some 300 ohm TV Twin lead? What could be better! It’s a half wave antenna that is also flexible and can be rolled up and packed! So he gave me a piece and I built one! Here are the instructions.
Well, it’s quite simple actually, the antenna can be broken into 3 parts (see diagram below):
At the bottom of the J, where it is shorted, the Open Wire Line (3) is at 0 Ohm, at the top, depending on the material, distance of the conductors, it could be upwards of 1000 Ohm on one side and infinite at the other. This creates a match between your half wave lengths Dipole (2). Where you decide to connect your SO-239 is where you get your line impedance match. This means you can connect a 50 ohm coax line and have it match the impedance of the antenna. This is why your connector appears to be so close to the shorted part of the “J”.
In closing, the J-Pole antenna is easy and fun to build. It is reliable, compact and can be adapted to many materials. Also, it’s Cheap to build. The complete build of my Copper pipe J-Pole cost me about 15$ to build. The TV Twin lead J-Pole was free (Thanks Tom!).
Why buy one when you can build your own!
Andre J Paquette (VE3PQE)