The most prominent of the early experimental stations was W1XER, originally an "Apex" radio station licensed to the Yankee Network, that was moved from Boston to the mountain in 1937, and initially used to relay meteorological information from the weather observatory. With the aid of Edwin H. Armstrong, the station was converted from an AM transmitter into an FM broadcasting station, although the conversion process turned out to be arduous undertaking, and W1XER did not start broadcast programming on a regular schedule until December 19, 1940. This station's facilities included construction of the original broadcast tower, the Yankee Building housing the crew and transmitter equipment, and the first power house building. Commercial broadcasting commenced on April 5, 1941, initially with the call sign W39B. Effective November 1, 1943 the station call sign was changed to WMTW, and in late 1946 the call letters were changed again, to WMNE. WMNE ceased operations in late 1948, due to excessive maintenance costs, and concern that a mandatory frequency change to the new FM "high band" would cause an unacceptable decrease in transmission range.