Electronic Filing
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MB E-Filing Site
These FCC/MB forms MUST be electronically filed:
FCC Forms 301, 301-CA, 302-CA, 302-FM, 302-DTV, 302-TV, 303-S, 314,
315, 316, 318, 319, 323, 323-E, 337, 340, 346, 347, 349,
350, 381
EEO Forms 395-A and 395-B have been suspended by
Commission Order FCC 01-34.
CDBS Users Guide or call (202)-418-2662
CDBS System Status
Call Sign Reservations & Authorizations
for broadcast
station call signs
Antenna Structure Registration via ULS
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Easy, one-stop access to all online U.S. Federal Government resources
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Radio Subcarriers SCAs
Subsidiary Communications Authority
A subcarrier, known also as
Subsidiary Communications
Authority or SCA,
is a separate audio or data channel which is transmitted along
with the main audio signal over a broadcast station. These subcarrier
channels are not receivable with a regular radio;
special receivers are required. Subcarriers are used for many
different purposes, including
(but not limited to) paging, inventory distribution, bus
dispatching, stock market reports,
traffic control signal switching, point-to-point or multipoint
messages, foreign language programming, radio reading services, radio broadcast data systems (RBDS), station
control and meter reading, utility load management, and muzak. A
broadcast station may transmit more than one subcarrier signal.
Licensing of subcarrier operations ended in 1983 when the service was
deregulated.
The Audio Division has prepared this fact sheet on broadcast
subcarriers to answer some of the more commonly received
questions on this subject.
The Commission does not keep records of which broadcast
stations are using subcarriers.
No Commission authorization, notice, application, or
license is required by the broadcast station
licensee wishing to transmit a subcarrier signal (see 47 CFR Section 73.127
for AM stations or 47 CFR Section 73.293
for FM stations). If the subcarrier signal is used for non-broadcast
purposes, the subcarrier user may require Commission authorization, as
follows:
Common Carrier use of a broadcast
subcarrier: The proposed user of the broadcast subcarrier must first seek
authorization from the Commission (Common Carrier Bureau) under
47 CFR Parts 21 & 22
(using FCC Form 600). After a 30 day notice period, the
Commission will issue a decision on the matter. The responsibility for initially
determining whether a particular activity is common carriage rests with the
broadcast licensee. See 47 CFR Section 73.127
for AM stations or 47 CFR Section 73.293
for FM stations.
- Private Carrier proposing use of a
broadcast subcarrier: The licensee of the broadcast
station (not the proposed subcarrier user) must
notify the Wireless Telecommunications Bureau in Gettysburg, PA by letter prior
to initiating service. The letter must certify that the subcarrier
facilities will only be used for permissible purposes
(47 CFR Parts 90 & 94).
For additional information, please call the
Wireless Telecommunications Bureau at 1-888-225-5322.
- Land Mobile Service
proposing use of a broadcast subcarrier: The licensee of the
broadcast station (not the
proposed subcarrier user) must notify the Wireless Telecommunications Bureau
in Gettysburg, PA by letter prior to initiating service. The letter
must certify that the subcarrier facilities will only be used for permissible
purposes, and must also certify that
the service will be open only to eligible users (47 CFR Part 90), and that
any interconnection with a telephone exchange (e.g, a paging system)
will be made in accordance with Section 331 of the Communications Act. For
additional information, please call the Wireless Telecommunications Bureau at
1-888-225-5322.
Private systems and common carrier systems
operating over a subcarrier channel may be exempt from
state & local regulation. For further information, please see the Memorandum Opinion and Order in Docket 82-536, FCC 94-187, 98 FCC 2d 792, released May 2, 1984.
Although the subcarrier user may seek the necessary authorization
for use, the
broadcast station remains responsible for the technical
operation, including the subcarriers.
The Commission does not regulate the programming content
of subcarriers. However, the broadcast
licensee not the subcarrier user, must retain
control of the programming, with the right to reject any
material that it deems inappropriate, undesirable or illegal. See 47 CFR Section 73.127(e)
for AM stations or 47 CFR Section 73.295(e)
for FM stations.
Subcarrier use is secondary to the transmission of the
main audio channel, and must not interfere with the main audio channel.
See 47 CFR Section 73.127(a)
for AM stations or 47 CFR Section 73.295(c)
for FM stations.
For FM stations only, subcarrier operation may continue when
the main channel (regular FM
programming) is off the air. However, the FM licensee
must continue the hourly identification procedures on the main channel
(see 47 CFR Section 73.1201).
The hourly announcement may be made by
a transmitter duty operator or by a time-clock-activated
recording.
Transmissions over the AM or FM station's subcarrier are not
required to comply with the station
identification, delayed recording, and sponsor identification
announcements required by
47 CFR Section 73.1201,
47 CFR Section 73.1208, and
47 CFR Section 73.1212. See
47 CFR Section 73.127(d)
for AM stations and 47 CFR Section 73.295(d)
for FM stations. In addition, there
is no program log requirement
for broadcast subcarrier use.
For monophonic FM stations, or when the main FM channel is
off, the multiplex subcarriers (two or more)
must be located between 20 kHz and 99 kHz. The arithmetic sum of all the
multiplex subcarriers may not exceed
30% modulation (22.5 kHz) (where 100% is 75 kHz deviation from the carrier
(or assigned center) frequency (see 47 CFR Section 73.310,
"Percentage Modulation"). The arithmetic sum of all multiplex
subcarriers above 75 kHz may not exceed 10% (7.5 kHz). See 47 CFR Section 73.319(a)(1),
(a)(3), (d)(1). and (d)(3).
For stereophonic FM stations, the multiplex subcarriers
(two or more) must be located between 53 kHz
and 99 kHz. The arithmetic sum of all multiplex subcarriers may
not exceed 20% modulation (15 kHz) (where
100% is 75 kHz deviation from the carrier). The arithmetic sum
of all subcarriers above 75 kHz may not exceed 10% (7.5 kHz). See 47 CFR Section 73.319(c)(2) and
(d)(2),
For FM stations only, the total peak
modulation may be
increased 0.5% for each 1.0% increase in subcarrier modulation.
Modulation levels up to 110% (82.5 kHz peak deviation) are
permitted for FM stations using subcarriers. (75 kHz deviation = 100%).
Instantaneous sidebands are permitted up to 99 kHz. See 47 CFR Section 73.1570(b)(2).
Technical specifications for subcarriers are no longer
contained in the FCC's Rules. However, because we receive occasional requests
for this information, the 1983 rules for subcarriers have been made available in a PDF document.
Educational stations may use subcarriers for profit-making
purposes. However, an educational FM
station is required to provide another subcarrier for any
radio reading services which may request such
use (47 CFR Section 73.593).
The educational station is limited to charging the radio
reading service for the fixed or operating costs, but may not charge on a for-profit
basis. For additional information regarding radio
reading services, see the Commission's Policy Statement, Docket 87-9, 3 FCC Record 6323, released 10/28/1988.
In general, tunable subcarrier receivers are prohibited
because they violate Section 605 of the Communications Act of 1934, as amended, which
states that no one may
receive, or assist in receiving, any radio communication to which
they are not entitled and
use that information for their own benefit. In addition, 18
U.S.C. Sections 2510 through
2521 prohibit the manufacture, assembly, possession, and sale of
any device primarily useful
for the surreptitious interception of such radio transmissions.
See KMLA
Broadcasting Corp. and Musicast, Inc. v. Twentieth Century
Cigarette Vendors Corp. 264 F. Supp. 35 (D. California 1967);
see also Letter to Dr. Haghighi from Richard B. Engelman, Chief, Technical Standards Branch, OET.
(One exception was made in 1984 for a tunable subcarrier receiver for a data
service in which (1) the
receivers could not receive other SCA transmissions, (2)
subscribers who had not met their
contractural obligations to the service provider were denied
access.)
Broadcast stations should keep copies of any subcarrier
leasing agreements at the
station. The agreements must be made available for
inspection by any authorized
representative of the FCC upon request. See 47 CFR Section 73.1226(c)
This document is located at
http://www.fcc.gov/mb/audio/subcarriers/index.html.
Documents pertaining to SCAs and Subcarriers is also available
at http://www.fcc.gov/mb/audio/decdoc/engrser.html#SUB.
Questions may be directed to Dale Bickel, dale.bickel@fcc.gov.
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