Sec.  74.535   Emission and bandwidth.

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

   (1) When using frequency modulation:

   (i) On any frequency removed from the assigned (center) frequency by more
   than 50% up to and including 100% of the authorized bandwidth: At least 25
   dB in any 100 kHz reference bandwidth (B[REF]);

   (ii) On any frequency removed from the assigned (center) frequency by more
   than 100% up to and including 250% of the authorized bandwidth: At least 35
   dB in any 100 kHz reference bandwidth;

   (iii) On any frequency removed from the assigned (center) frequency by more
   than 250% of the authorized bandwidth: At least 43+10 log[10] (P[MEAN] in
   watts) dB, or 80 dB, whichever is the lesser attenuation, in any 100 kHz
   reference bandwidth.

   (2) When using transmissions employing digital modulation techniques:

   (i) For operating frequencies below 15 GHz, in any 4 kHz reference bandwidth
   (B[REF]), 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(G − 50) + 10 Log[10] B.

   (Attenuation greater than 80 decibels is not required.)

   Where:

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

   G = Percent removed from the carrier frequency.

   B = Authorized bandwidth in megahertz.

   (ii) For operating frequencies above 15 GHz, in any 1 MHz reference
   bandwidth (B[REF]), 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 11 decibels:

   A = 11 + 0.4(G − 50) + 10 Log[10] B.

   (Attenuation greater than 56 decibels is not required.)

   (iii) In any 4 kHz reference bandwidth (B[REF]), 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] (P[MEAN] in watts) decibels,
   or 80 decibels, whichever is the lesser attenuation.

   (b) For all emissions not covered in paragraph (a) of this section, the peak
   power of emissions shall be attenuated below the peak envelope transmitter
   power (P[PEAK]) in accordance with the following schedule:

   (1) On any frequency 500 Hz inside the channel edge up to and including 2500
   Hz outside the same edge, the following formula will apply:

   A = 29 Log[10] [(25/11)[(D + 2.5 − (W/2)] ^2 ] dB

   (Attenuation greater than 50 decibels is not required.)

   Where:

   A = Attenuation (in dB) below the peak envelope transmitter power.

   D = the displacement frequency (kHz) from the center of the authorized
   bandwidth.

   W = the channel bandwidth (kHz).

   (2) On any frequency removed from the channel edge by more than 2500 Hz: At
   least 43+10 Log[10] (P[PEAK] in watts) dB.

   (c) In the event a station's emissions outside its authorized channel cause
   harmful interference, the Commission may require the licensee to take such
   further steps as may be necessary to eliminate the interference.

   (d) For purposes of compliance with the emission limitation requirements of
   this section:

   (1) If the transmitter modulates a single carrier, digital modulation
   techniques are considered as being employed when digital modulation occupies
   50 percent or more of the total peak frequency deviation of a transmitted
   radio frequency carrier. The total peak frequency deviation will be
   determined by adding the deviation produced by the digital modulation signal
   and the deviation produced by any frequency division multiplex (FDM)
   modulation used. The deviation (D) produced by the FDM signal must be
   determined in accordance with  Sec. 2.202(f) of this chapter.

   (2) If the transmitter modulates two or more carriers, with at least one
   using digital modulation and one using frequency or other analog modulation,
   digital modulation techniques are considered as being employed when the
   necessary bandwidth of the digital signal(s) is 50 percent or more of the
   aggregate bandwidth of the system, comprising the digital necessary
   bandwidth(s), the analog necessary bandwidth(s), and any bandwidth(s)
   between the digital and analog necessary bandwidths. In this case, the
   aggregate bandwidth shall be used for the authorized bandwidth (B) in
   paragraph (a) of this section, and for purposes of compliance with the
   bandwidth limitations in  Sec. 74.502 of this subpart; and the sum of the powers
   of the analog and digital signals shall be used for mean transmitter power
   (P[MEAN]) in paragraph (a) or the peak envelope transmitter power (P[PEAK])
   in paragraph (b) of this section, and for purposes of compliance with the
   power limitations in  Sec. 74.534 of this subpart.

   (3) For demonstrating compliance with the attenuation requirements for
   frequency modulation and digital modulation in paragraph (a) of this
   section, the resolution bandwidth (B[RES]) of the measuring equipment used
   for measurements removed from the center frequency by more than 250 percent
   of the authorized bandwidth shall be 100 kHz for operating frequencies below
   1 GHz, and 1 MHz for operating frequencies above 1 GHz. The resolution
   bandwidth for frequencies removed from the center frequency by less than 250
   percent of the authorized bandwidth shall be the reference bandwidth
   (B[REF]) specified in the individual emission limitations, but may be
   reduced to not less than one percent of the authorized bandwidth (B),
   adjusted upward to the nearest greater resolution bandwidth available on the
   measuring equipment. In all cases, if B[RES] and B[REF] are not equal, then
   the attenuation requirement must be increased (or decreased) as determined
   by a factor of 10 log[10] [(B[REF] in megahertz)/(B[RES] in megahertz)]
   decibels, where a positive factor indicates an increase in the attenuation
   requirement and a negative factor indicates a decrease in the attenuation
   requirement.

   (4) Stations licensed pursuant to an application filed before March 17,
   2005, using equipment not conforming with the emission limitations specified
   above, may continue to operate indefinitely in accordance with the terms of
   their current authorizations, subject to periodic renewal. Existing
   equipment and equipment of product lines in production before April 16,
   2003, authorized via certification or verification before March 17, 2005,
   for equipment not conforming to the emission limitations requirements
   specified above, may continue to be manufactured and/or marketed, but may
   not be authorized for use under a station license except at stations
   licensed pursuant to an application filed before March 17, 2005. Any
   non-conforming equipment authorized under a station license, and replaced on
   or after March 17, 2005, must be replaced by conforming equipment.

   (e) The following limitations apply to the operation of aural broadcast
   microwave booster stations:

   (1) The booster station must receive and amplify the signals of the
   originating station and retransmit them on the same frequency without
   significantly altering them in any way. The characteristics of the booster
   transmitter output signal shall meet the requirements applicable to the
   signal of the originating station.

   (2) The licensee is responsible for correcting any condition of interference
   that results from the radiation of radio frequency energy outside the
   assigned channel. Upon notice by the FCC to the station licensee that
   interference is being caused, operation of the apparatus must be immediately
   suspended and may not be resumed until the interference has been eliminated
   or it can be demonstrated that the interference is not due to spurious
   emissions. However, short term test transmissions may be made during the
   period of suspended operation to determine the efficacy of remedial
   measures.

   (3) In each instance where suspension of operation is required, the licensee
   must submit a full report to the FCC after operation is resumed. The report
   must contain details of the nature of the interference, the source of
   interfering signals, and the remedial steps taken to eliminate the
   interference.

   [ 28 FR 13716 , Dec. 14, 1963, as amended at  48 FR 50332 , Nov. 1, 1983;  49 FR 7130 , Feb. 27, 1984;  49 FR 37777 , Sept. 26, 1984;  50 FR 48599 , Nov. 26,
   1985;  68 FR 12766 , March 17, 2003.]