SPARC holds a monthly 2m simplex net. Many of us also have 6m capability which we wish to explore. To this end we will use two club meetings to build 6m antennas, then test them following a future 2m simplex net.
In this build we will aim for low SWR in the 50.3 to 50.6 MHz region of the band. This region is designated as “all modes” in the 6-meter band plan. If you’d like to target a different area of the band, you will need to make adjustments. This is accomplished during the tuning process by lengthening or shortening the radiating element. (It will be cut on the long side, and we will trim. So “lengthening” really means “not trimming as much.”) The J-Pole design does not have a broad resonant region, so targeting your desired operating region will be necessary.
Click here for a nice online calculator for J-Poles made strictly from ladder line.
The build that we will be doing uses ladder line only for the matching section, so the calculator is somewhat off. The ladder line has a velocity factor of 0.91, while the 14-gauge silicone wire that we use for the radiating section has a velocity factor of 0.97. This means that our radiating section should be about 1.066 (0.97/0.91) times longer than the ladder line design.
This YouTube video explains a similar build:
Below is a handout featuring full instructions for the build.
At our April meeting we will tune the antenna using a mast and an analyzer.