40/80m Magnetic Loop
My next project in July of 2025 was a “magloop” antenna targeting the 40-meter and 80-meter bands. Since our balcony is very small, no other antenna options would realistically work here.
My first feed attempt was with a coupling loop, which didn't work at all, most likely because of all of the metal in the vicinity.
Next up was a toroid coil, making the whole system into a transformer.
Another feed I tried was a gamma match. (I'm not sure why I didn't immediately pursue the toroid coil route when it worked better than the coupling loop.)
Since the toroid coil from earlier worked better, I ended up going back to that route, albeit with far fewer turns, which almost worked!
My final choice of feed for this incarnation of this magloop was “The Doohickey”: a box with a switch between two different taps on the toroid coil, as the impedance match needed to be different based on the desired frequency range.
And it was paired with the addition of a second vacuum capacitor to bring the resonant frequency of the loop down. (I intended to put a switch on that could add or remove the second capacitor, but I've yet to get to this at the time of writing.)
