Download the MFJ-915 Manual The MFJ-915 RF Isolator is a 1:1 Current Balun designed to be placed in line with a 50-Ohm coax. The RF Isolator is effective from 1.8 to 30 MHz. It was designed to improve the performance of all amateur stations, fixed or mobile. MFJ-915 will reduce or eliminate stray RF often found on coax. This stray RF can cause burns and other problems with electronic equipment in ham-shacks and vehicles. Stray RF also results in a loss of radiated power from the antenna, which will lead to a great reduction in signal strength. Use of the MFJ-915 will increase the efficiency of all amateur stations. Made up of 50 Ferrite Core Beads, placed onto a 13-inch piece of RG-303 coax. The coax and SO-239 connectors have Teflon(R) for maximum insulation and extended life of the product. The RF Isolator is enclosed in schedule 40 PVC pipe for maximum strength and protection.