10$ portable HF 10-28 MHz magnetic loop antenna "wild strawberry"

thingiverse

This is fully 3D printed portable magnetic loop antenna including 3D printed sliding variable capacitor, which can sustain around 40W CW. The goal is to assemble it into a backpack, walk or cycle with it, and then quickly disassemble it. It should also be as light and as cheap as possible. Managed to tune it from the 30m band up to the 10m band, SWR is around 1.8 on the 30m band going down to 1.1 on the 10m. On a 5W field strength meter, it goes full scale at 3 meters. Had successful QSOs in CW on the 20m band with this antenna from the bushes. You will need 7mm diameter fiberglass poles from an unused tent, which are used as holders for the large ring. Large and small rings are made from the same twin cable, just split up to a small ring touching point (see photos) and cut for a small ring. A large ring diameter is around 0.9 m. It's better to use higher AWG cables, it will increase antenna efficiency. Also, using a 1:1 balun, as had some troubles with currents reaching the mic on my homebrew radio. Capacitor instructions could be found in another thing description at https://www.thingiverse.com/thing:4024253 A piece of 20 mm cable pipe is used as a holder, also it is used as a storage for tent poles when disassembled, so cut it to the same size as your tent poles or a little bit longer. The complete price of this antenna is around $10, which includes cable, filament, tent poles, aluminum sheet for capacitor plates, BNC connector, M3 screws and bolts. Most likely, you already have all these components.