My first magnetic loop for 2m :)

Really simple construction: bent ca. 2mm brass pipe soldered directly to the outside of an SMA plug, inside of the plug soldered to the red wire as “input coil”. Tunable by squeezing the ends more or less close together.

SWR of <1.2 at resonance, not bad. Impedance is at roughly 44+j2 Ohm, also not bad for totally eyeballing it without any prior calculations.

I can reach the nearest 2m relais just fine at 2W, although to be fair I can do the same with a short whip antenna. More testing to follow. Holy shit, this actually works!

  • LH0ezVTOP
    32·
    8 days ago

    Sadly I just have an FM radio, but maybe I’ll try it at the local club station. I am not sure how much power it will survive, though.

    • shortwavesurfer@lemmy.zip
      42·
      8 days ago

      Good point. Remember that FM is 100% duty cycle where sideband is not. But you definitely do need to keep the power down in order to not fry something on the antenna itself. If you’re not careful, you can get arcing between the plates.

      • LH0ezVTOP
        22·
        8 days ago

        Especially since the “plates” are just some overlapping pieces of the brass coil covered in heatshrink… It makes me wonder how to make a 70cm loop, at that point, the capacity would be so small, I might get away with a horseshoe design of some kind.