Goto Section: 74.636 | 74.638 | Table of Contents
FCC 74.637
Revised as of December 4, 2012
Goto Year:2011 |
2013
§ 74.637 Emissions and emission limitations.
(a) The mean power of emissions shall be attenuated below the mean
transmitter power (PMEAN ) 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 (BREF );
(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 log10 (PMEAN
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 (BREF ), 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 ā 50) + 10 Log10 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 (BREF ), 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 (Gā50) + 10 Log10 B.
(Attenuation greater than 56 decibels is not required.)
(iii) In any 4 kHz reference bandwidth (BREF ), the center frequency of
which is removed from the assigned frequency by more than 250 percent
of the authorized bandwidth: At least 43 +10 Log10 (PMEAN in watts)
decibels, or 80 decibels, 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.
(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 (PPEAK ) 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 Log10 [(25/11)[(D + 2.5 ā (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 Log10 (PPEAK in watts) dB.
(c) 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 § 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 paragraph (g)
of this section and in § 74.602 of this subpart; and the sum of the
powers of the analog and digital signals shall be used for mean
transmitter power (PMEAN ) in paragraph (a) or the peak envelope
transmitter power (PPEAK ) in paragraph (b) of this section, and for
purposes of compliance with the power limitations in § 74.636 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 (BRES ) 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 (BREF ) 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 BRES and BREF are not equal, then the attenuation requirement
must be increased (or decreased) as determined by a factor of 10 log10
[(BREF in megahertz)/(BRES 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.
(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 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.
Frequency Band (MHz) Maximum authorized bandwidth (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
[ 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; 68 FR 12769 , Mar.
17, 2003.]
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Goto Section: 74.636 | 74.638
Goto Year: 2011 |
2013
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