All antennas need a common mode balun. Especially OCF dipole (sometimes
called Windom) needs enough common mode reactance because the feeding point
is "hot" - not in the zero RF. Here is an enhanced balun for OCF dipole.
The two toroids make the 1:4 impedance transformation and the additional
common mode balun provides extra common mode impedance to avoid feeding line
to act as an antenna. This balun may help a lot to attenuate local noise
compared to other OCF dipole baluns.
Note1: This design is for 80 meter as a lowest band. If you want to make it for 160 meter increase the toroidal core winding to 2 x 16 turns or use Amidon FT-140-43 cores. Additionally use two of those common baluns in series.
Note2: Take care to connect the toroidal core windings correctly. Input windings in parallel and ouput windings in series!
Note1: This design is for 80 meter as a lowest band. If you want to make it for 160 meter increase the toroidal core winding to 2 x 16 turns or use Amidon FT-140-43 cores. Additionally use two of those common baluns in series.
Note2: Take care to connect the toroidal core windings correctly. Input windings in parallel and ouput windings in series!
Enhanced OCF Dipole Balun Schematics
Enhanced OCF Dipole Balun Drawing. Click the drawing to enlarge.
Constructed OCF dipole balun with rain shield. Click the picture to enlarge.