The FCC authorized Edwin Howard Armstrong to operate an experimental FM station at Alpine, New Jersey (call sign W2XMN), providing a high-profile platform to refine and publicize wideband FM broadcasting.
Armstrong’s Alpine station W2XMN began experimental broadcasts in June 1938, becoming an early proving ground for FM transmitter/receiver development and propagation studies.
W2XMN aired a widely noted public broadcast relaying programming from New York City’s WQXR, helping demonstrate FM’s improved audio quality and noise resistance to the public.
In Massachusetts, station W1XOJ (Yankee Network) began a regular daily schedule, illustrating early regional investment beyond Armstrong’s New York-area demonstrations.
NBC’s experimental facility W2XWG began regular FM broadcasting, signaling that major networks were actively evaluating FM as a broadcast medium.
The FCC authorized a commercial FM broadcast band—42–50 MHz, with the lowest channels reserved for educational use—setting a national regulatory framework for FM’s expansion.
The FCC issued the first 15 construction permits for commercial FM stations, accelerating station-building and formalizing early market entry in multiple U.S. cities.
The FCC’s initial FM allocation went into effect, with commercial and educational stations beginning operations on the 42–50 MHz “low band.”
The University of Illinois’ FM station (then WIUC, later WILL-FM) began regular operations, marking an early milestone for university and noncommercial participation in FM broadcasting.
Armstrong’s Alpine site expanded into the new “high band” with station W2XEA (later KE2XCC), supporting the transition to the post-1945 FM allocation.
The FCC decided to move FM from 42–50 MHz to what became the modern 88–108 MHz band, a controversial change that ultimately reshaped receiver markets and station engineering for decades.
FM broadcasters began operating on the higher frequencies during the transition period following the 1945 reallocation, as stations and manufacturers adapted equipment to the new band plan.
A multi-station “exclusively FM” network program demonstrated FM’s viability for broader distribution beyond single-market broadcasting during the postwar expansion phase.
The FCC’s transition period ended and remaining 42–50 MHz FM broadcasters were required to cease low-band operations, fully consolidating FM broadcasting into the higher VHF band.
The FCC issued its final order adopting the Zenith/GE multiplex system for FM stereophonic broadcasting, enabling compatible stereo rollout across North American FM while preserving mono compatibility.
With educational allocations positioned at the bottom of the postwar FM band, noncommercial educational FM expanded substantially in the postwar decades, becoming a significant part of U.S. FM broadcasting by the early 1960s.
Development and Spread of FM Radio in North America (1935–1970)
