A Detroit Apex Station in 1936 (W8XWJ) by John Schneider, September 17, 2013. (radioworld.com) Pre-History: Detroit's Experimental Amplitude Modulation (AM) "Apex" Station, W8XWJ (michiguide.com) FCC History Cards for W8XWJ (covering 1936–1941) Apex Radio in Milwaukee (W9XAZ) (jeff560.tripod.com) Apex and FM chronology (jeff560.tripod.com) "High Frequency Broadcast Stations in the United States" (Licensed by FCC as of January 1, 1937), Broadcasting Yearbook (1937 edition), page 331. "High Frequency (Apex) Broadcast Stations in the United States" (authorized by FCC as of January 1, 1938), Broadcasting Yearbook (1938 edition), page 290. "High Frequency (Apex) Broadcast Stations in the United States" (authorized by FCC as of January 1, 1939), Broadcasting Yearbook (1939 edition), page 369. (jeff560.tripod.com) "High Frequency Broadcasting Stations in the United States" (Authorized by FCC as of January 15, 1940), Broadcasting Yearbook (1940 edition), page 374. High Frequency and FM broadcast stations in the U.S. in 1942 Radio Annual (jeff560.tripod.com) "Sarkes Tarzian and His HiFAM Experiment" by Andrew Mitz, Radio Age, July 2004. Radio technology Radio in the United States History of radio 1930s in American music Telecommunications-related introductions in 1934 Bandplans Broadcast engineering