FCC 2.1049 as of October 1, 2005

Goto Section: 2.1047 | 2.1051 | Table of Contents

FCC 2.1049
Revised as of October 1, 2005
Goto Year:2004 | 2006

Sec. 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.

(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.

(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
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
Number of message circuits that modulate the average power (Pavg) level test
transmitter signal shall exceed the
Limits of Pavg (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 240............... X+4 log10 Nc...................
X: -5.6 to -1.0
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 nu
mber of circuits in the
multiplexed message load. Pavg shall be selected by the transmitter manufactu
rer and included with the
technical data submitted with the application for type acceptance. (See Sec. 2.2
02(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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