A device for protecting a radio frequency transmission line from transient voltages includes an inner conductor for transmitting electromagnetic signals of a desired frequency band and a grounded, coaxial outer conductor electrically insulated from the inner conductor. A conductive bus bar extends longitudinally within the outer conductor and is conductively connected thereto. A plurality of gas discharge tubes are directly mounted on the inner conductor along at least a portion of its length in spaced apart intervals. In addition, each of the plurality of gas discharge tubes is conductively connected to a flattened surface on the bus bar through a metal spring washer. In use, the plurality of gas discharge tubes operate in parallel with one another to discharge transient voltages carried by the inner conductor that exceed a predefined threshold.