|Enhanced OCF Dipole Balun 2014-07-10 OH7SV
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!
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.