[BC] Type acceptance

Thu Nov 18 06:28:01 CST 2010

Transmitters used in AM/FM/TV broadcast service in the US are required
by 73.1660 to be "verified," not "type accepted."

As the topic of the thread leading up to this post is based on modifying
an FM transmitter after it had been type-verified with the FCC by its
manufacturer, below are some considerations for doing thisassembled
from the FCC website, in logical order.

Please note that these references may not be complete, or even current -
but they were copied and pasted together from the FCC site today, Nov 18, 2010.

Sec 2.09 (d) may be a surprise:
 \ \ If, because of modifications performed subsequent to
authorization, a new party becomes responsible for ensuring that a
product complies with the technical standards and the new party does not
obtain a new equipment authorization, the equipment shall be labelled,
following the specifications in Sec. 2.925(d), with the following:
"This product has been modified by [insert name, address and telephone
number of the party performing the modifications].'' / /

This clip from Sec 2.593 also may be a surprise (especially the 2nd sentence
in it):
 \ \ (d) Verified equipment shall be reverified if any modification or
change adversely affects the emanation characteristics of the modified
equipment. The party designated in Sec. 2.909 bears responsibility for
continued compliance of subsequently produced equipment. / /

Before I retired I was part of the Harris team that was responsible for
assembling the measurements and documents neededto support the FCC
verification of FM transmitters.  There was considerably more to it than
just "doing a proof" in the usualsense.  For example complete measurements
were taken at a low, mid,and high frequency in the 88-108 MHz band, and
included cabinet radiationmeasurements at an open-area test site
as well as conductednoise appearing on the a-c mains (and more).

It might be justified for those wanting to comply with the letter of the law
when modifying a broadcast transmitter to have an FCC attorney research
this process thoroughly and accurately for them, before they proceed.

RF

+ + + +

Quotes from the Rules:

PART 73_RADIO BROADCAST SERVICES

          Subpart H_Rules Applicable to All Broadcast Stations

Sec. 73.1660  Acceptability of broadcast transmitters.

    (a)(1) An AM, FM, or TV transmitter shall be verified for compliance
with the requirements of this part following the procedures described in
part 2 of this chapter.
      (b) A permittee or licensee planning to modify a transmitter which
has been approved by the FCC or verified for compliance must follow the
requirements contained in Sec. 73.1690.
      (e) Additional rules covering certification and verification,
modification of authorized transmitters, and withdrawal of a grant of
authorization are contained in part 2 of the FCC rules.

Sec. 73.1690  Modification of transmission systems.

    The following procedures and restrictions apply to licensee
modifications of authorized broadcast transmission system facilities.
    (a) The following changes are prohibited:
    (1) Those that would result in the emission of signals outside of
the authorized channel exceeding limits prescribed for the class of
service.
    (2) Those that would cause the transmission system to exceed the
equipment performance measurements prescribed for the class of service
(AM, Sec. 73.44; FM, Sec. Sec. 73.317, 73.319, and 73.322; TV and
Class A TV, Sec. Sec. 73.682 and 73.687).

                     Subpart B_FM Broadcast Stations

Sec. 73.317  FM transmission system requirements.

    (a) FM broadcast stations employing transmitters authorized after
January 1, 1960, must maintain the bandwidth occupied by their emissions
in accordance with the specification detailed below. FM broadcast
stations employing transmitters installed or type accepted before
January 1, 1960, must achieve the highest degree of compliance with
these specifications practicable with their existing equipment. In
either case, should harmful interference to other authorized stations
occur, the licensee shall correct the problem promptly or cease
operation.
    (b) Any emission appearing on a frequency removed from the carrier
by between 120 kHz and 240 kHz inclusive must be attenuated at least 25
dB below the level of the unmodulated carrier. Compliance with this
requirement will be deemed to show the occupied bandwidth to be 240 kHz
or less.
    (c) Any emission appearing on a frequency removed from the carrier
by more than 240 kHz and up to and including 600 kHz must be attenuated
at least 35 dB below the level of the unmodulated carrier.
    (d) Any emission appearing on a frequency removed from the carrier
by more than 600 kHz must be attenuated at least 43 + 10
Log10 (Power, in watts) dB below the level of the unmodulated
carrier, or 80 dB, whichever is the lesser attenuation.
    (e) Preemphasis shall not be greater than the impedance-frequency
characteristics of a series inductance resistance network having a time
constant of 75 microseconds. (See upper curve of Figure 2 of Sec.
73.333.)

Sec. 73.319  FM multiplex subcarrier technical standards.

    (a) The technical specifications in this Section apply to all
transmissions of FM multiplex subcarriers except those used for
stereophonic sound broadcasts under the provisions of Sec. 73.322.
    (b) Modulation. Any form of modulation may be used for subcarrier
operation.
    (c) Subcarrier baseband. (1) During monophonic program
transmissions, multiplex subcarriers and their significant sidebands
must be within the range of 20 kHz to 99 kHz.
    (2) During stereophonic sound program transmissions (see Sec.
73.322), multiplex subcarriers and their significant sidebands must be
within the range of 53 kHz to 99 kHz.
    (3) During periods when broadcast programs are not being
transmitted, multiplex subcarriers and their significant sidebands must
be within the range of 20 kHz to 99 kHz.
    (d) Subcarrier injection. (1) During monophonic program
transmissions, modulation of the carrier by the arithmetic sum of all
subcarriers may not exceed 30% referenced to 75 kHz modulation
deviation. However, the modulation of the carrier by the arithmetic sum
of all subcarriers above 75 kHz may not modulate the carrier by more
than 10%.
    (2) During stereophonic program transmissions, modulation of the
carrier by the arithmetic sum of all subcarriers may not exceed 20%
referenced to 75 kHz modulation deviation. However, the modulation of
the carrier by the arithmetic sum of all subcarriers above 75 kHz may
not modulate the carrier by more than 10%.
    (3) During periods when no broadcast program service is transmitted,
modulation of the carrier by the arithmetic sum of all subcarriers may
not exceed 30% referenced to 75 kHz modulation deviation. However, the
modulation of the carrier by the arithmetic sum of all subcarriers above
75 kHz may not modulate the carrier by more than 10%.
    (4) Total modulation of the carrier wave during transmission of
multiplex subcarriers used for subsidiary communications services must
comply with the provisions Sec. 73.1570(b).
    (e) Subcarrier generators may be installed and used with a type
accepted FM broadcast transmitter without specific authorization from
the FCC provided the generator can be connected to the transmitter
without requiring any mechanical or electrical modifications in the
transmitter FM exciter circuits.
    (f) Stations installing multiplex subcarrier transmitting equipment
must ensure the proper suppression of spurious or harmonic radiations.
See Sec. Sec. 73.317, 73.1590 and 73.1690. If the subcarrier operation
causes the station's transmissions not to comply with the technical
provisions for FM broadcast stations or causes harmful interference to
other communication services, the licensee or permittee must correct the
problem promptly or cease operation. The licensee may be required to
verify the corrective measures with supporting data. Such data must be
retained at the station and be made available to the FCC upon request.

Sec. 73.322  FM stereophonic sound transmission standards.

    (a) An FM broadcast station shall not use 19 kHz +/-20 Hz, except as
 the stereophonic pilot frequency in a
transmission system meeting the following parameters:
    (1) The modulating signal for the main channel consists of the sum
of the right and left signals.
    (2) The pilot subcarrier at 19 kHz +/-2 Hz, must
frequency modulate the main carrier between the limits of 8 and 10
percent.
    (3) One stereophonic subcarrier must be the second harmonic of the
pilot subcarrier (i.e., 38 kHz) and must cross the time axis with a
positive slope simultaneously with each crossing of the time axis by the
pilot subcarrier. Additional stereophomic subcarriers are not precluded.
    (4) Double sideband, suppressed-carrier, amplitude modulation of the
stereophonic subcarrier at 38 kHz must be used.
    (5) The stereophonic subcarrier at 38 kHz must be suppressed to a
level less than 1% modulation of the main carrier.
    (6) The modulating signal for the required stereophonic subcarrier
must be equal to the difference of the left and right signals.
    (7) The following modulation levels apply:
    (i) When a signal exists in only one channel of a two channel
(biphonic) sound transmission, modulation of the carrier by audio
components within the baseband range of 50 Hz to 15 kHz shall not exceed
45% and modulation of the carrier by the sum of the amplitude modulated
subcarrier in the baseband range of 23 kHz to 53 kHz shall not exceed
45%.
    (ii) When a signal exists in only one channel of a stereophonic
sound transmission having more than one stereophonic subcarrier in the
baseband, the modulation of the carrier by audio components within the
audio baseband range of 23 kHz to 99 kHz shall not exceed 53% with total
modulation not to exceed 90%.
    (b) Stations not transmitting stereo with the method described in
(a), must limit the main carrier deviation caused by any modulating
signals occupying the band 19 kHz +/-20 Hz to 125 Hz.
    (c) All stations, regardless of the stereophonic transmission system
used, must not exceed the maximum modulation limits specified in Sec.
73.1570(b)(2). Stations not using the method described in (a), must
limit the modulation of the carrier by audio components within the audio
baseband range of 23 kHz to 99 kHz to not exceed 53%.

PART 2--FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS;
GENERAL RULES AND REGULATIONS

              Subpart J--Equipment Authorization Procedures

Sec.  2.902  Verification.

    (a) Verification is a procedure where the manufacturer makes
measurements or takes the necessary steps to insure that the equipment
complies with the appropriate technical standards. Submittal of a sample
unit or representative data to the Commission demonstrating compliance
is not required unless specifically requested by the Commission pursuant
to Sec. 2.957, of this part.
    (b) Verification attaches to all items subsequently marketed by the
manufacturer or importer which are identical as defined in Sec.  2.908
to the sample tested and found acceptable by the manufacturer.

Sec.  2.909  Responsible party.

    The following parties are responsible for the compliance of radio
frequency equipment with the applicable standards:
      (b) In the case of equipment subject to authorization under the
verification procedure, the manufacturer or, in the case of imported
equipment, the importer. If subsequent to manufacture and importation,
the radio frequency equipment is modified by any party not working under
the authority of the responsible party, the party performing the
modification becomes the new responsible party.
    (d) If, because of modifications performed subsequent to
authorization, a new party becomes responsible for ensuring that a
product complies with the technical standards and the new party does not
obtain a new equipment authorization, the equipment shall be labelled,
following the specifications in Sec. 2.925(d), with the following:
``This product has been modified by [insert name, address and telephone
number of the party performing the modifications].''

PART 2--FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS;
GENERAL RULES AND REGULATIONS

              Subpart J--Equipment Authorization Procedures

Sec.  2.925  Identification of equipment.

    (a) Each equipment covered in an application for equipment
authorization shall bear a nameplate or label listing the following:
    (1) FCC Identifier consisting of the two elements in the exact order
specified in Sec.2.926. The FCC Identifier shall be preceded by the
term FCC ID in capital letters on a single line, and shall be of a type
size large enough to be legible without the aid of magnification.

    Example: FCC ID XXX123. XXX--Grantee Code 123--Equipment Product
Code

    (2) Any other statements or labeling requirements imposed by the
rules governing the operation of the specific class of equipment, except
that such statement(s) of compliance may appear on a separate label at
the option of the applicant/grantee.

    (d) In order to validate the grant of equipment authorization, the
nameplate or label shall be permanently affixed to the equipment and
shall be readily visible to the purchaser at the time of purchase.
    (1) As used here, permanently affixed means that the required
nameplate data is etched, engraved, stamped, indelibly printed, or
otherwise permanently marked on a permanently attached part of the
equipment enclosure. Alternatively, the required information may be
permanently marked on a nameplate of metal, plastic, or other material
fastened to the equipment enclosure by welding, riveting, etc., or with
a permanent adhesive. Such a nameplate must be able to last the expected
lifetime of the equipment in the environment in which the equipment will
be operated and must not be readily detachable.
    (2) As used here, readily visible means that the nameplate or
nameplate data must be visible from the outside of the equipment
enclosure. It is preferable that it be visible at all times during
normal installation or use, but this is not a prerequisite for grant of
equipment authorization.

Sec.  2.953  Responsibility for compliance.

    (a) In verifying compliance, the responsible party, as defined in
Sec.  2.909 warrants that each unit of equipment marketed under the
verification procedure will be identical to the unit tested and found
acceptable with the standards and that the records maintained by the
responsible party continue to reflect the equipment being produced under
such verification within the variation that can be expected due to
quantity production and testing on a statistical basis.
    (d) Verified equipment shall be reverified if any modification or
change adversely affects the emanation characteristics of the modified
equipment. The party designated in Sec. 2.909 bears responsibility for
continued compliance of subsequently produced equipment.
  ///