Sec. 74.637  Emissions and emission limitations.

    (a) For frequency modulation, the mean power of emissions shall be 
attenuated below the mean transmitter power (P) in accordance with the 
following schedule:
    (1) On any frequency removed from the assigned frequency by more 
than 50% and up to 100% of the authorized bandwidth: at least 25 dB.
    (2) On any frequency removed from the assigned frequency by more 
than

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100% and up to 150% of the authorized bandwidth: at least 35 dB.
    (3) On any frequency removed from the assigned frequency by more 
than 150% of the authorized bandwidth: at least 43+10 Log(P) dB.
    (b) For all emissions except frequency modulation, the peak power of 
emissions shall be attenuated below the peak envelope transmitter power 
(P) 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:
[GRAPHIC] [TIFF OMITTED] TC13NO91.023


or 50 dB whichever is the lesser attenuation. Where: D is the 
displacement frequency (kHz) from the center of the authorized 
bandwidth; and W is the channel bandwidth (kHz).
    (2) On any frequency removed from the channel edge by more than 2500 
Hz: At least 43+10 Log (P) dB.
    (c) For operation in the bands 6425-6525 MHz, 17,700-19,700 MHz, and 
31,000-31,300 MHz: TV broadcast STL, relay and booster stations may be 
authorized to employ analog or digital modulation in this band. The mean 
power of any emission shall be attenuated below the mean output power of 
the transmitter 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;
    (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;
    (iii) On any frequency removed from the assigned (center) frequency 
by more than 250% of the authorized bandwidth: At least 43+10 log 10 
(mean output power in watts) dB, or 80 dB, whichever is the lesser 
attenuation.
    (2) When using digital modulation:
    (i) In any 1 NHz band, the center frequency of which is removed from 
the assigned frequency by more than 50% up to and including 250% of the 
authorized bandwidth: As specified by the following equation but in no 
event less than 11 dB.

                  A=11+0.4 (P-50)+10 log10 B

where:

A=Attenuation (in dB) below the mean output power level
P=Percent removed from the carrier frequency
B=Authorized bandwidth in MHz

    [Attenuation greater than 56 decibels is not required.]
    (ii) In any 4 kHz band, the center frequency of which is removed 
from the assigned frequency by more than 250% of the authorized 
bandwidth: At least 43=10 log10 (mean output power in watts) 
dB, or 80 dB, whichever is the lesser attenuation.
    (3) Amplitude Modulation.
    For vestigial sideband AM video: On any frequency removed from the 
center frequency of the authorized band by more than 50%: at least 50 dB 
below peak power of the emission.
    (d) In the event that interference to other stations is caused by 
emissions outside the authorized channel, the FCC may require greater 
attenuation than that specified in paragraph (b) of this section.
    (e) The following limitations also apply to the operation of TV 
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

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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.
    (f) 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.
    (g) The maximum bandwidth which will be authorized per frequency 
assignment is set out in the table which follows. Regardless of the 
maximum authorized bandwidth specified for each frequency band, the 
Commission reserves the right to issue a license for less than the 
maximum bandwidth if it appears that less bandwidth would be sufficient 
to support an applicant's intended communications.

                                                                        
------------------------------------------------------------------------
                                            Maximum authorized bandwidth
           Frequency Band (MHz)                         (MHz)           
------------------------------------------------------------------------
1,990 to 2,110............................  18                          
6,425 to 6,525............................  25                          
6,875 to 7,125............................  25                          
12,700 to 13,250..........................  25                          
17,700 to 19,700..........................  80                          
31,000 to 31,300..........................  25 or 50                    
38,600 to 40,000..........................  ............................
------------------------------------------------------------------------


[ 45 FR 78692 , Nov. 26, 1980, as amended at  48 FR 50734 , Nov. 3, 1983;  49 FR 7131 , Feb. 27, 1984;  49 FR 37778 , Sept. 26, 1984;  50 FR 7342 , Feb. 
22, 1985;  50 FR 34150 , Aug. 23, 1985;  50 FR 48600 , Nov. 26, 1985;  52 FR 7142 , Mar. 9, 1987;  58 FR 51251 , Oct. 1, 1993]