Dipole Center Insulator
Date: March 25, 2010
Some time ago I built a j-pole antenna. It is currently my only radio antenna. I wanted to find an easier antenna to build for myself and something I can recommend to new operators. I guess it's the new ham in me but I wanted something new.
I tried to build a 2m yagi antenna. I was using PVC for the boom and 1/8 steel rods for the elements. I could not get the element to line up straight and they kept moving. I just could not get it to stay together. I was not going to bother with it if it kept giving me problems.
That when I realized that I was going about it in the wrong way. You need to learn how to craw before you can walk. A yagi antenna is a dipole on a boom with one or more elements. So I needed to build and master the dipole before moving on to make a yagi or any other antenna.
After reading a few section of the 2009 ARRL Handbook I came across a simple dipole. For 2m the wire or elements each need to be about 19 1/2" long. Some 20" of wire and some coax cable should do the trick. But I just didn't want to build it and be done with it. I wanted something I could reuse.
I decided to make a center insulator that I could use for future antennas. I bought a SO-239, wire connectors, two telescoping antennas. The rest of the items I already had on hand. They were a plastic platform, toroid and some copper wire.
Insulator with Telescoping Antennas
First find a place on your plastic platform to put your SO-239 and the wire connectors. Drill your holes and mount them. Next I made a 1:1 balun using the toroid and two copper wires. I soldered one end of the balun to the SO-239 and the other end to the wire connectors. That should be it. You now have a center insulator for dipoles. I am not sure what the rating is so I will keep it for low power.
Now on to the reason I made this center insulator. I installed the telescoping antennas to each connector and extended them to 19 1/2” long and checked the SWR. Great SWR for a simple 2m dipole, just make sure you have it vertical and not horizontal.