Being in COVID-19 lockdown gives me the opportunity to be on the air during the day, once work time is over. I tried a magmount 20m Diamond mobile antenna on the East-facing balcony, but I managed one contact with my sloppy CW. Well, RBN receivers had me around Europe. But no contacts were possible in PSK31, neither a report on pskreporter service!
So I moved to something different: a magnetic loop. It had to be build with readily available materials: a hula-loop diameter 70 cm (then not needed to keep it in shape), 4 mm solid coax cable (it's too thin for a permanent loop!), a dual-gang air variable capacitor (two sections in series giving 10-130 pF) and FT817 to tune the antenna
sur place.
The feeding loop is just a piece of coax "1/5th of the main loop" long. From the coaxial line, the center goes to braid of the small loop on one side, and the coax braid to the braid on the other side. In other words the feedline is terminated with a 44 cm long loop made of thick wire.
It took me a couple of hours to build. Most of the time was spent looking and implementing a solid mechanical solution for the variable capacitor.
The picture shows the resulting loop. It tunes 30 to 10m. On 20m it is about 20 kHz wide for 2 SWR bars on the FT817.
