Sec. 73.72  Operating during the experimental period.

    (a) An AM station may operate during the experimental period (the 
time between midnight and sunrise, local time) on its assigned frequency 
and with its authorized power for the routine testing and maintenance of 
its transmitting system, and for conducting experimentation under an 
experimental authorization, provided no interference is caused to other 
stations maintaining a regular operating schedule within such period.
    (b) No station licensed for ``daytime'' or ''specified hours'' of 
operation may broadcast any regular or scheduled program during this 
period.
    (c) The licensee of an AM station shall operate or refrain from 
operating its station during the experimental period as directed by the 
FCC to facilitate frequency measurements or for the determination of 
interference.

[ 43 FR 32780 , July 28, 1978, as amended at  56 FR 64859 , Dec. 12, 1991]