Goto Section: 74.636 | 74.638 | Table of Contents
FCC 74.637
Revised as of October 2, 2015
Goto Year:2014 |
2016
§ 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: 2014 |
2016
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