English: Closeup of joint between mast sections of antenna tower of AM radio station KBRC, located in Mount Vernon, Washington State, USA. The steel lattice antenna towers of AM radio stations like this function as mast radiators; the radio current from the transmitter is applied directly to the mast, and the whole mast serves as the antenna. The tower is assembled from sections that are bolted together. To ensure that the entire tower is a single conductor, the sections are bonded electrically at the joints with short jumpers. In this case, copper strips have been soldered between the vertical risers.