Sec. 2.989  Measurements required: Occupied bandwidth.

    The occupied bandwidth, that is the frequency bandwidth such that, 
below its lower and above its upper frequency limits, the mean powers 
radiated are each equal to 0.5 percent of the total mean power radiated 
by a given emission shall be measured under the following conditions as 
applicable:
    (a) Radiotelegraph transmitters for manual operation when keyed at 
16 dots per second.
    (b) Other keyed transmitters--when keyed at the maximum machine 
speed.
    (c) Radiotelephone transmitters equipped with a device to limit 
modulation or peak envelope power shall be modulated as follows. For 
single sideband and independent sideband transmitters, the input level 
of the modulating signal shall be 10 dB greater than that necessary to 
produce rated peak envelope power.
    (1) Other than single sideband or independent sideband 
transmitters--when modulated by a 2500 Hz tone at an input level 16 dB 
greater than that necessary to produce 50 percent modulation. The input 
level shall be established at the frequency of maximum response of the 
audio modulating circuit.
    (2) Single sideband transmitters in A3A or A3J emission modes--when 
modulated by two tones at frequencies of 400 Hz and 1800 Hz (for 3.0 kHz 
authorized bandwidth), or 500 Hz and 2100 Hz (for 3.5 kHz authorized 
bandwidth), or 500 Hz and 2400 Hz (for 4.0 kHz authorized bandwidth), 
applied simultaneously. The input levels of the tones shall be so 
adjusted that the two principal frequency components of the radio 
frequency signal produced are equal in magnitude.
    (3) Single sideband transmitters in the A3H emission mode--when 
modulated by one tone at a frequency of 1500 Hz (for 3.0 kHz authorized 
bandwidth), or 1700 Hz (for 3.5 kHz authorized bandwidth), or 1900 Hz 
(for 4.0 kHz authorized bandwidth), the level of which is adjusted to 
produce a radio frequency signal component equal in magnitude to the 
magnitude of the carrier in this mode.
    (4) As an alternative to paragraphs (c) (2) and (3) of this section, 
other tones besides those specified may be used as modulating 
frequencies, upon a sufficient showing of need. However, any tones so 
chosen must not be harmonically related, the third and fifth order 
intermodulation products which occur must fall within the -25 dB step of 
the emission bandwidth limitation curve, the seventh and ninth order 
products must fall within the -35 dB step of the referenced curve and 
the eleventh and all higher order products must fall beyond the -35 dB 
step of the referenced curve.
    (5) Independent sideband transmitters having two channels--when 
modulated by 1700 Hz tones applied simultaneously to both channels. The 
input levels of the tones shall be so adjusted

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that the two principal frequency components of the radio frequency 
signal produced are equal in magnitude.
    (d) Radiotelephone transmitters without a device to limit modulation 
or peak envelope power shall be modulated as follows. For single 
sideband and independent sideband transmitters, the input level of the 
modulating signal should be that necessary to produce rated peak 
envelope power.
    (1) Other than single sideband or independent sideband 
transmitters--when modulated by a 2500 Hz tone of sufficient level to 
produce at least 85 percent modulation. If 85 percent modulation is 
unattainable, the highest percentage modulation shall be used.
    (2) Single sideband transmitters in A3A or A3J emission modes--when 
modulated by two tones at frequencies of 400 Hz and 1800 Hz (for 3.0 kHz 
authorized bandwidth), or 500 Hz and 2100 Hz (for 3.5 kHz authorized 
bandwidth), or 500 Hz and 2400 Hz (for 4.0 kHz authorized bandwidth), 
applied simultaneously. The input levels of the tones shall be so 
adjusted that the two principal frequency components of the radio 
frequency signal produced are equal in magnitude.
    (3) Single sideband transmitters in the A3H emission mode--when 
modulated by one tone at a frequency of 1500 Hz (for 3.0 kHz authorized 
bandwidth), or 1700 Hz (for 3.5 kHz authorized bandwidth), or 1900 Hz 
(for 4.0 kHz authorized bandwidth), the level of which is adjusted to 
produce a radio frequency signal component equal in magnitude to the 
magnitude of the carrier in this mode.
    (4) As an alternative to paragraphs (d) (2) and (3) of this section, 
other tones besides those specified may be used as modulating 
frequencies, upon a sufficient showing of need. However any tones so 
chosen must not be harmonically related, the third and fifth order 
intermodulation products which occur must fall within the -25 dB step of 
the emission bandwidth limitation curve, the seventh and ninth order 
products must fall within the -35 dB step of the referenced curve and 
the eleventh and all higher order products must fall beyond the -35 dB 
step of the referenced curve.
    (5) Independent sideband transmitters having two channels--when 
modulated by 1700 Hz tones applied simultaneously to both channels. The 
input levels of the tones shall be so adjusted that the two principal 
frequency components of the radio frequency signal produced are equal in 
magnitude.
    (e) Transmitters for use in the Radio Broadcast Services:
    (1) AM broadcast transmitters for monaural operation--when amplitude 
modulated 85% by a 7,500 Hz input signal.
    (2) AM broadcast stereophonic operation--when the transmitter 
operated under any stereophonic modulation condition not exceeding 100% 
on negative peaks and tested under the conditions specified in 
Sec. 73.128 in part 73 of the FCC rules for AM broadcast stations.
    (3) FM broadcast transmitter not used for multiplex operation--when 
modulated 85 percent by a 15 kHz input signal.
    (4) FM broadcast transmitters for multiplex operation under 
Subsidiary Communication Authorization (SCA)--when carrier is modulated 
70 percent by a 15 kHz main channel input signal, and modulated an 
additional 15 percent simultaneously by a 67 kHz subcarrier 
(unmodulated).
    (5) FM broadcast transmitter for stereophonic operation--when 
modulated by a 15 kHz input signal to the main channel, a 15 kHz input 
signal to the stereophonic subchannel, and the pilot subcarrier 
simultaneously. The input signals to the main channel and stereophonic 
subchannel each shall produce 38 percent modulation of the carrier. The 
pilot subcarrier should produce 9 percent modulation of the carrier.
    (6) Television broadcast monaural transmitters--when modulated 85% 
by a 15 kHz input signal.
    (7) Television broadcast stereophonic sound transmitters--when the 
transmitter is modulated with a 15 kHz input signal to the main channel 
and the stereophonic subchannel, any pilot subcarrier(s) and any 
unmodulated auxiliary subcarrier(s) which may be provided. The signals 
to the main channel and the stereophonic subchannel must be 
representative of the system

[[Page 530]]

being tested and when combined with any pilot subcarrier(s) or other 
auxiliary subcarriers shall result in 85% deviation of the maximum 
specified aural carrier deviation.
    (f) Transmitters for which peak frequency deviation (D) is 
determined in accordance with Sec. 2.202(f), and in which the modulating 
baseband comprises more than 3 independent speech channels--when 
modulated by a test signal determined in accordance with the following:
    (1) A modulation reference level is established for the 
characteristic baseband frequency. (Modulation reference level is 
defined as the average power level of a sinusoidal test signal delivered 
to the modulator input which provides the specified value of per-channel 
deviation.)
    (2) Modulation reference level being established, the total rms 
deviation of the transmitter is measured when a test signal consisting 
of a band of random noise extending from below 20 kHz to the highest 
frequency in the baseband, is applied to the modulator input through any 
preemphasis networks used in normal service. The average power level of 
the test signal shall exceed the modulation reference level by the 
number of decibels determined using the appropriate formula in the 
following table:

------------------------------------------------------------------------
                                 Number of dB by                        
                                which the average                       
                                power (Pavg) level                      
  Number of message circuits    test signal shall      Limits of Pavg   
that modulate the transmitter       exceed the             (dBm0)       
                                    modulation                          
                                 reference level                        
------------------------------------------------------------------------
More than 3, but less than 12  To be specified by   ....................
                                the equipment                           
                                manufacturer                            
                                subject to FCC                          
                                approval.                               
At least 12, but less than 60  X+2 log10 Nc.......  X: -2 to +2.6    
   
At least 60, but less than     X+4 log10 Nc.......  X: -5.6 to -1.0  
   
 240.                                                                   
240 or more..................  X+10 log10 Nc......  X: -19.6 to -15.0
   
------------------------------------------------------------------------
Where X represents the average power in a message circuit in dBm0; Nc is
  the number of circuits in the multiplexed message load. Pavg shall be 
  selected by the transmitter manufacturer and included with the        
  technical data submitted with the application for type acceptance.    
  (See Sec.  2.202(e) in this chapter.)                                 

    (g) Transmitters in which the modulating baseband comprises not more 
than three independent channels--when modulated by the full complement 
of signals for which the transmitter is rated. The level of modulation 
for each channel should be set to that prescribed in rule parts 
applicable to the services for which the transmitter is intended. If 
specific modulation levels are not set forth in the rules, the tests 
should provide the manufacturer's maximum rated condition.
    (h) Transmitters employing digital modulation techniques--when 
modulated by an input signal such that its amplitude and symbol rate 
represent the maximum rated conditions under which the equipment will be 
operated. The signal shall be applied through any filter networks, 
pseudo-random generators or other devices required in normal service. 
Additionally, the occupied bandwidth shall be shown for operation with 
any devices used for modifying the spectrum when such devices are 
optional at the discretion of the user.
    (i) Transmitters designed for other types of modulation--when 
modulated by an appropriate signal of sufficient amplitude to be 
representative of the type of service in which used. A description of 
the input signal should be supplied.

(Secs. 4, 303, 307, 48 Stat., as amended, 1066, 1082, 1083; 47 U.S.C. 
154, 303, )
[39 307 FR 5919 , Feb. 15, 1974, as amended at  39 FR 35664 , Oct. 3, 1974;  47 FR 13164 , Mar. 29, 1982;  48 FR 16493 , Apr. 18, 1983;  49 FR 18105 , Apr. 
27, 1984]