Every antenna needs a choke balun in the feeding point! This applies to all antennas like dipoles, yagis, loops, OCF dipoles, ground planes, slopers etc. Without a common mode balun there is always some common mode RF current in the feeding cable which will disturb the antenna radiation pattern and the very important thing is that the feeding cable picks up local man made noise during reception. Additionally a common mode balun is reducing the RF field in ham shack and helps rigs to work properly.

Read this good article www.balundesigns.com/reference/all-about-the-11-currentchoke-balun



You just need a ferrite toroid and wind the feeding coaxial cable thru it. The purpose is to achieve enough common mode impedance to attenuate common mode RF current in the feeding cable. 500 ohms is better than no choke balun, 1000 ohms and up is preferred. In fact the reqiured common mode impedance is depending on the load impedance - thump rule is to achieve 20 to 40 times the antenna impedance.

The basic construction principle of a 1:1 common mode balun. Note the two different winding styles.

Here is a more compact construction which is using a ferrite tube (Axial Ferrite Bead) instead of a toroidal core. See an 3.5MHz application here.