Build: Trapped Vertical for 12, 17, and 30 Meters (QRP)
Three bands was not enough.
A Drawing for the Lazy
Here’s all you need if you want to do the build and you’re the adventurous type:
The bill of materials is the same except that you’ll need roughly 52 feet of wire this time around. Remember: 30 ft is just for the radials.
Note that you get 30pF by using 3x 10pF capacitors in parallel. The same way, you get 47pF by using a 27pF capacitor and adding 2x 10pf capacitors in parallel.
Some Caveats
This build will not fit on my 20 ft fishing pole. I’m tempted to add some loading to the 30 meter section to make the overall length shorter.
I haven’t taken this out into the field yet, but I suspect I’ll need to have a better ground plane.
I’m tempted to remove a single winding from the 17 meter trap. I felt like I had everything dialed in with the prototype (built from recycled wire). When I went to build it with my “good” wire, I had a hard time getting resonance low enough, even with the coils as pinched as I could get them. It’s also possible that the wire itself isn’t long enough. So just keep that in mind if you build it.