When used in a portable operation, if the antenna is slanted upward with rain present, then drops of water will gather on the radiator and travel down to the operating position.  The Drip Dams are a 100% Black Acetal(non-conductive) spring loaded locking device that is slid over the wire and is easily repositioned.  It will cause the water to shed off of the cable by acting as a Dam where ever it is placed.