For Static-Free Broadcasting - Workers adjust a new "Cloverleaf" antenna designed for frequency modulation radio transmitters by the Bell Laboratories in America. Static-free broadcasting - known as frequency modulation is being rapidly extended and developed in the U.S.A., where 500 cities of 47 State will soon be able to avail themselves of the service. Construction of new stations, coupled with improved technical advances, will bring the new service within reach of million of new listeners. Frequency modulation radio waves follow a line-of-sight path, and travel only to the horizon. July 29, 1947. (Photo by Fox).