Intro: J-Pole Antennas for 144 and 440
Since my rotor snapped and my 2m quad fell with it I needed a simple temporary antenna
I made a couple of plumber's delight J-poles
see here: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCoQFjAA&url=http%3A%2F%2Fharriscountyares.org%2Ftraining%2FKNW%2FKNW-110.pdf&ei=j0MpU7nOH8L10gGVhICICw&usg=AFQjCNEszt63Wl4qVRVMslXPZ8B_R4Iz_Q&sig2=ZMVu1bfhali7gGoTyCznlA&bvm=bv.62922401,d.dmQ
I cut some for 144 MHz and a couple of more for 440 MHz
Since there's still almost 3 feet of snow in my yard I put one on top of a fence post outside my window. It worked so well it's going up to the roof after the thaw
Step 1: Selecting Parts
For 144 MHz I used 3/4 copper tubing for the main element and a 3/4 to 1/2 tee so I could use 1/2 inch tubing for the stub
For 440 it's all 1/2 tubing. The tee had to but trimmed so I could get the proper spacing
I added copper sweat to threaded couplers on the bottom so I could use some black pipe fittings and flanges for mounting. I could have used galvanized but I plan on tack welding then painting them. Welding galvanized fittings is not the best thing to do especially in a confined space.
Step 2: Attaching Connectors
I used #12 copper wire and plastic spring clamps to temporarily attach an so239 for tuneup
After I got the best swr I screwed the connector on with one screw then soldered the connector in place and sealed it with RTV
I also made a couple with a BNC connectors for use with a handheld and one with an F connector for a low power ATV setup
Step 3: Final Steps
Before getting out the ladder I like to prep the ends of the cable with some kind of ferrite choke. Those split types you get with computer monitors are ok and the best for larger solid coax.
I like big toroid rings because they are easy to loop the cable around and it holds its shape pretty well. Add a wire tie if it tries to unravel
I used pipe fittings to mount it on top of the fence post for testing but I plan to use a 90 degree elbow to attach it to the eve. I'll tack weld the horizontal fittings in place so it doesn't tip over. If you don't have a welder just pin them with screws
First try was impressive. I turned the sensitivity all the way up on my old MFJ SWR meter and it's a perfect match. At 1w I can hit a repeater almost 20 miles away with a clean signal.
We finally got nice weather and I was able to mount them up on the roof. They work pretty well and don't seem to interfere with each other.