RF in the shack can make operating difficult and in some cases impossible. A RF Choke can help keep the rf currents from flowing on the outer braid of the coax. Many Hams just use a bunch of ferrites close to the feed point. Another method is the open air choke. These are easy to build and cheap.
As a project, I wanted to make an open air choke to use for portable operations. Also,a friend of mine is having some issues with rf and I wanted to test a choke that is constructed of 25′ of 50 coax. BNC connectors will be placed on the ends for quick connecting and disconnecting. I made a second version that I have used in the past on 2 meters. It is constructed the same way but uses 40″ of 50 ohm coax.