It didn’t take long after my first successful attempt at receiving weather satellite broadcasts for me to realize that I would need a much better antenna. I had been using a 1/4 wave whip with a 4-wire ground plane. There performance out of this antenna was poor. I read up on QFH (Quadrifiliar Helix antennas) from many of the high quality posts from around the world. I took what I could from these implementations, and did my best with the supplies I had available.
I ultimately started with whatever PVC pipe I had lying around; it ended up being 1-1/4″ outside diameter garden-variety PVC. Next, I went onto the excellent QFH antenna calculator. This site already has the defaults for a good 137 MHz antenna, and I didn’t change them. Next I measured the diameter of my pipe (in mm) and printed out the drilling templates using their drilling template generator.
Pick a point for the top line of the template and scribe a line perfectly parallel with the axis of the pipe. This is easy if you use the “estes door jamb trick.” For those that haven’t built a model rocket recently, you put the pipe in a door jamb crease.
This right-angle will make the pipe perfectly square and you can mark a line. Also, you can use a piece of angle stock, as this guy did. Make sure that all your template strips line up with this line. Next mark the holes’ letter with pen on the pipe. This is your reference for where the wires need to go. Finally, drill the holes. I only drilled the top and bottom holes, and I didn’t make them as big as the template said. The template (and the calculator) suggest using 3/8″ soft copper tubing, but I didn’t have any of that around, and it costs a lot more than the #10 ground wire that I used.
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