§  2.1049   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 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 §  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 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 §  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 message circuits that modulate the transmitter Number of dB
   by which the average power (P[avg]) level test signal shall exceed the
   modulation reference level Limits of P[avg](dBm0)
   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 log[10]N[c] X: −2 to +2.6
   At least 60, but less than 240 X+4 log[10]N[c] X: −5.6 to −1.0
   240 or more X+10 log[10]N[c] X: −19.6 to −15.0

   Where X represents the average power in a message circuit in dBm0;
   N[c]is the number of circuits in the multiplexed message load.
   P[avg]shall be selected by the transmitter manufacturer and included
   with the technical data submitted with the application for type
   acceptance. (See §  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, 307)

   [ 39 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. Redesignated at  63 FR 36599 , July 7, 1998]

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