FOUR NEW EMI RFI cylindrical slip-on ferrite core chokes. Ferrite material with excellent broadband filter characteristics (75ohm nominal suppression @ 25MHz, 150ohm @ 100MHz, 275ohm @ 300MHz). Slip onto power, antenna, or microphone cabling to reduce electromagnetic interference. Large 0.43" ID fits over RG-8, RG-213, LMR-400 style coax and larger AC power cables. Measures 0.43"(ID) x 0.73" (OD) x 0.675" (L) Cylindrical chokes can be used to reduce high frequency interference caused by home electronics (radio transmitter, telephone, television, audio equipment, and more). The innovative snap-on design makes it easy to install on most any type of equipment by snapping around antenna cables, power cords, speaks cables, microphone cables, telephone cords, computer cables, and more. The line choke reduces line transmitted electromagnetic interference (EMI) and transmitted radio frequency interference (RFI). Line transmitted interference is often caused by motors in appliances such as blenders, garbage disposals, and others. The noise is conducted through the AC power wiring. To reduce this type of noise, connect the snap-on choke around the AC power cord as close to the appliance generating the noise as practical. Radio frequency interference occurs when the cable leads of the home appliance acts as an antenna to pick-up transmitted RF signals often caused by nearby radio transmission such as a radio or TV station, CB or HAM radio. To reduce this kind of noise snap-on the choke as close as possible to the appliance being interfered with as practical. Interference by CB and HAM radio transmitters may be caused from radiation from unbalanced antenna cables and and noise can be coupled into the microphone cabling. A choke on the antenna and microphone cables helps to reduce the problems. As a general rule, the more chokes placed on the cabling, or more wraps of the cable around the choke, the more effective the noise reduction. Visit our eBay store for other radio accessories.