According to Radio Broadcasting at Union College, amateur station 2ADD's debut concert broadcast occurred on October 14, 1920. At some later point the broadcasts were shifted to the college's experimental station, 2XQ.
 
QST, December, 1920, page 64:

Radio  Communications  By  The  Amateurs
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RADIOPHONE  CONCERTS
_______
Union  College  Radio  Club,
Schenectady,  N. Y.,
22  October  1920.
Mr.  Kenneth  B.  Warner,
        Hartford,  Conn.
Dear  Sir:
    The Radio Club at Union College, Schenectady, N. Y., is transmitting a radio concert every Thursday evening from 8:00 to 8:30 and from 9:00 to 9:30 Eastern Standard Time, on 350 meters, signing 2ADD.
    We radiate over 3 amperes with five General Electric "V" Tubes. The Club would be greatly obliged if you could print this notice among the "QST" pages in an early issue.
Respectfully  yours,
            Jetson  O.  Bentley,
                        Secretary.
Address  mail:
Jetson  O.  Bentley
        Lambda  Chi  Alpha  House,
                22  Gillespie  St.
                        Schenectady,  N. Y.