Have you ever had one of those moments while looking at something and going "hmm, I wonder if this will antenna??" Well, while I was disassembling a couple old mountain bikes for scrap one day, I had that thought while looking at the rims on one of the bikes. It was 26" in diameter, and made out of aluminum. I quickly found myself with my bolt cutters, removing all the spokes.
I made a coupling loop from 12ga solid copper wire stripped from a piece of 12/3 house wiring, and used a BNC to binding post adapter to fit it to the loop. The rim and coupling loop were screwed to a couple pieces of scrap wood I found nearby.
After cutting a notch in the rim about 1" wide, I found an air variable capacitor in my junk box and attached it between the gap with a couple short pieces of wire. After hooking up the analyzer, I found there was not enough capacitance to tune it to 20 meters. The best I could tune it to was in the high 15 MHz range. I found my bag of Russian doorknob capacitors, and found one that I could add to the air variable cap and finally tune all of the 20 meter band.
My first contact on the antenna was while using my Xiegu X5105 QRP rig at 5 watts. It was a phone contact with an operator in Mississippi during the Mississippi QSO Party. To say he was a little surprised would be an understatement!!! See what I mean in the video below.
I do like to pull this antenna out from time to time, and even used it on a POTA activation once.
Sometimes I'll look at something and think "hmm, I wonder if it will antenna??"