Sec.  21.106   Emission limitations.

   

   (a) The mean power of emissions shall be attenuated below the mean
   output power of the transmitter in accordance with the following
   schedule:

   (1) When using transmissions other than those employing digital
   modulation techniques:

   (i) On any frequency removed from the assigned frequency by more than
   50 percent up to and including 100 percent of the authorized
   bandwidth: At least 25 decibels;

   (ii) On any frequency removed from the assigned frequency by more than
   100 percent up to and including 250 percent of the authorized
   bandwidth: At least 35 decibels;

   (iii) On any frequency removed from the assigned frequency by more
   than 250 percent of the authorized bandwidth: At least 43+10 Log 10
   (mean output power in watts) decibels, or 80 decibels, whichever is
   the lesser attenuation.

   (2) When using transmissions employing digital modulation techniques
   (see Sec. 21.122(b)) in situations other than those covered by subpart K
   of this part:

   (i) For operating frequencies below 15 GHz, in any 4 kHz band, the
   center frequency of which is removed from the assigned frequency by
   more than 50 percent up to and including 250 percent of the authorized
   bandwidth: As specified by the following equation but in no event less
   than 50 decibels. A=35+0.8(P;minus;50)+10 Log 10 B. (Attenuation
   greater than 80 decibels is not required.)

   where:

   A=Attenuation (in decibels) below the mean output power level.

   P=Percent removed from the carrier frequency.

   B=Authorized bandwidth in MHz.

   (ii) In any 4 kHz band, the center frequency of which is removed from
   the assigned frequency by more than 250 percent of the authorized
   bandwidth: At least 43+10 Log 10 (mean output power in watts)
   decibels, or 80 decibels, whichever is the lesser attenuation.

   (b) When an emission outside of the authorized bandwidth causes
   harmful interference, the Commission may, at its discretion, require
   greater attenuation than specified in paragraph (a) of this section.

   [ 44 FR 60534 , Oct. 19, 1979, as amended at  46 FR 23450 , Apr. 27, 1981;
    52 FR 23550 , June 23, 1987;  61 FR 26675 , May 28, 1996;  65 FR 46617 ,
   July 31, 2000]