4:1 current baluns are designed to replace the center insulator of a dipole antenna. They are made up of two large low-permeability ferrite cores. The MFJ-913 is rated at 300 watts. Their SO-239 coax connectors have Teflon™ internal insulation for maximum insulation and extended life of the product. Unlike some other baluns, the MFJ-913 make direct electrical connections to the antenna with #14 stranded copper wire and are enclosed in Schedule-40 PVC for maximum strength and support of a dipole antenna.
A current balun can reduce or eliminate stray RF often found on coax. This stray RF can cause burns and other problems with electronic equipment while reducing antenna radiation. Installation of an MFJ-913 current balun can increase the efficiency of any amateur station.