§ 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, § 73.44; FM, § § 73.317, 73.319, and 73.322; TV and Class A TV,
   § § 73.682 and 73.687).

   (b) The following changes may be made only after the grant of a
   construction permit application on FCC Form 301 for commercial stations
   or Form 340 for noncommercial educational stations:

   (1) Any construction of a new tower structure for broadcast purposes,
   except for replacement of an existing tower with a new tower of
   identical height and geographic coordinates.

   (2) Any change in station geographic coordinates, including coordinate
   corrections of more than 3 seconds latitude and/or 3 seconds longitude.
   FM and TV directional stations must also file a construction permit
   application for any move of the antenna to another tower structure
   located at the same coordinates.

   (3) Any change which would require an increase along any azimuth in the
   composite directional antenna pattern of an FM station from the
   composite directional antenna pattern authorized (see § 73.316), or any
   increase from the authorized directional antenna pattern for a TV
   broadcast (see § 73.685) or Class A TV station (see § 73.6025).

   (4) Any change in the directional radiation characteristics of an AM
   directional antenna system. See § 73.45 and § 73.150.

   (5) Any decrease in the authorized power of an AM station or the ERP of
   a TV or Class A TV station, or any decrease or increase in the ERP of
   an FM commercial station, which is intended for compliance with the
   multiple ownership rules in § 73.3555.

   (6) For FM noncommercial educational stations, any of the following:

   (i) Any increase in the authorized maximum ERP, whether horizontally or
   vertically polarized, for a noncommercial educational FM station
   operating on Channels 201 through 220, or a Class D FM station
   operating on Channel 200.

   (ii) For those FM noncommercial educational stations on Channels 201 to
   220, or a Class D FM station operating on Channel 200, which are within
   the separation distances specified in Table A of § 73.525 with respect
   to a Channel 6 television station, any increase in the horizontally or
   vertically polarized ERP from the presently authorized ERP.

   (iii) For those FM noncommercial educational stations on Channels 201
   through 220 which are located within the separation distances in
   § 73.525 with respect to a Channel 6 television station, or a Class D FM
   station operating on Channel 200, any decrease in the presently
   authorized horizontal effective radiated power which would eliminate
   the horizontal ERP to result in use of vertical ERP only.

   (iv) For those FM noncommercial educational stations which employ
   separate antennas for the horizontal ERP and the vertical ERP, mounted
   at different heights, the station may not increase or decrease either
   the horizontal ERP or the vertical ERP without a construction permit.

   (7) Any increase in the authorized ERP of a television station, Class A
   television station, FM commercial station, or noncommercial educational
   FM station, except as provided for in § 73.1690(c)(4), (c)(5), or
   (c)(7), or in § 73.1675(c)(1) in the case of auxiliary facilities.

   (8) A commercial TV or noncommercial educational TV station operating
   on Channels 14 or Channel 69 or a Class A TV station on Channel 14 may
   increase its horizontally or vertically polarized ERP only after the
   grant of a construction permit. A television or Class A television
   station on Channels 15 through 21 within 341 km of a cochannel land
   mobile operation, or 225 km of a first-adjacent channel land mobile
   operation, must also obtain a construction permit before increasing the
   horizontally or vertically polarized ERP (see part 74, § 74.709(a) and
   (b) for tables of urban areas and corresponding reference coordinates
   of potentially affected land mobile operations).

   (9) Any change in the community of license, where the proposed new
   facilities are the same as, or would be mutually exclusive with, the
   licensee's or permittee's present assignment.

   (c) The following FM, TV and Class A TV station modifications may be
   made without prior authorization from the Commission. A modification of
   license application must be submitted to the Commission within 10 days
   of commencing program test operations pursuant to § 73.1620. With the
   exception of applications filed solely pursuant to paragraphs (c)(6),
   (c)(9), or (c)(10) of this section, the modification of license
   application must contain an exhibit demonstrating compliance with the
   Commission's radio frequency radiation guidelines. In addition, except
   for applications solely filed pursuant to paragraphs (c)(6) or (c)(9)
   of this section, where the installation is located on or near an AM
   tower, as defined in § 1.30002, an exhibit demonstrating compliance with
   § 1.30003 or § 1.30002, as applicable, is also required.

   (1) Replacement of an omnidirectional antenna with one of the same or
   different number of antenna bays, provided that the height of the
   antenna radiation center is not more than 2 meters above or 4 meters
   below the authorized values. Any concurrent change in ERP must comply
   with § 73.1675(c)(1), 73.1690(4), (c)(5), or (c)(7). Program test
   operations at the full authorized ERP may commence immediately upon
   installation pursuant to § 73.1620(a)(1).

   (2) Replacement of a directional FM antenna, where the measured
   composite directional antenna pattern does not exceed the licensed
   composite directional pattern at any azimuth, where no change in
   effective radiated power will result, and where compliance with the
   principal coverage requirements of § 73.315(a) will be maintained by the
   measured directional pattern. The antenna must be mounted not more than
   2 meters above or 4 meters below the authorized values. The
   modification of license application on Form 302-FM to cover the antenna
   replacement must contain all of the data in the following sections (i)
   through (v). Program test operations at one half (50%) power may
   commence immediately upon installation pursuant to § 73.1620(a)(3).
   However, if the replacement directional antenna is an exact replacement
   (i.e., no change in manufacturer, antenna model number, AND measured
   composite antenna pattern), program test operations may commence
   immediately upon installation at the full authorized power.

   (i) A measured directional antenna pattern and tabulation on the
   antenna manufacturer's letterhead showing both the horizontally and
   vertically polarized radiation components and demonstrating that
   neither of the components exceeds the authorized composite antenna
   pattern along any azimuth.

   (ii) Contour protection stations authorized pursuant to § 73.215 or
   § 73.509 must attach a showing that the RMS (root mean square) of the
   composite measured directional antenna pattern is 85% or more of the
   RMS of the authorized composite antenna pattern. See § 73.316(c)(9). If
   this requirement cannot be met, the licensee may include new relative
   field values with the license application to reduce the authorized
   composite antenna pattern so as to bring the measured composite antenna
   pattern into compliance with the 85 percent requirement.

   (iii) A description from the manufacturer as to the procedures used to
   measure the directional antenna pattern. The antenna measurements must
   be performed with the antenna mounted on a tower, tower section, or
   scale model equivalent to that on which the antenna will be permanently
   mounted, and the tower or tower section must include transmission
   lines, ladders, conduits, other antennas, and any other installations
   which may affect the measured directional pattern.

   (iv) A certification from a licensed surveyor that the antenna has been
   oriented to the proper azimuth.

   (v) A certification from a qualified engineer who oversaw installation
   of the directional antenna that the antenna was installed pursuant to
   the manufacturer's instructions.

   (3) A directional TV on Channels 2 through 13 or 22 through 68 or a
   directional Class A TV on Channels 2 through 13 or 22 through 51, or a
   directional TV or Class A TV station on Channels 15 through 21 which is
   in excess of 341 km (212 miles) from a cochannel land mobile operation
   or in excess of 225 km (140 miles) from a first-adjacent channel land
   mobile operation (see part 74, § 74.709(a) and (b) for tables of urban
   areas and reference coordinates of potentially affected land mobile
   operations), may replace a directional TV or Class A TV antenna by a
   license modification application, if the proposed horizontal
   theoretical directional antenna pattern does not exceed the licensed
   horizontal directional antenna pattern at any azimuth and where no
   change in effective radiated power will result. The modification of
   license application on Form 302-TV or Form 302-CA must contain all of
   the data set forth in § 73.685(f) or § 73.6025(a), as applicable.

   (4) Commercial and noncommercial educational FM stations operating on
   Channels 221 through 300 (except Class D), NTSC TV stations operating
   on Channels 2 through 13 and 22 through 68, Class A TV stations
   operating on Channels 2 through 13 and 22 through 51, and TV and Class
   A TV stations operating on Channels 15 through 21 that are in excess of
   341 km (212 miles) from a cochannel land mobile operation or in excess
   of 225 km (140 miles) from a first-adjacent channel land mobile
   operation (see part 74, § 74.709(a) and (b) for tables of urban areas
   and reference coordinates of potentially affected land mobile
   operations), which operate omnidirectionally, may increase the
   vertically polarized effective radiated power up to the authorized
   horizontally polarized effective radiated power in a license
   modification application. Noncommercial educational FM licensees and
   permittees on Channels 201 through 220, that do not use separate
   antennas mounted at different heights for the horizontally polarized
   ERP and the vertically polarized ERP, and are located in excess of the
   separations from a Channel 6 television station listed in Table A of
   § 73.525(a)(1), may also increase the vertical ERP, up to (but not
   exceeding) the authorized horizontally polarized ERP via a license
   modification application. Program test operations may commence at full
   power pursuant to § 73.1620(a)(1).

   (5) Those Class A FM commercial stations which were permitted to
   increase ERP pursuant to MM Docket No. 88-375 by a modification of
   license application remain eligible to do so, provided that the station
   meets the requirements of § 73.1690 (c)(1) and is listed on one of the
   Public Notices as authorized to increase ERP, or by a letter from the
   Commission's staff authorizing the change. These Public Notices were
   released on November 3, 1989; November 17, 1989; December 8, 1989;
   March 2, 1990; and February 11, 1991. The increased ERP must comply
   with the multiple ownership requirements of § 73.3555. Program test
   operations may commence at full power pursuant to § 73.1620(a)(1).

   (6) FM contour protection stations authorized pursuant to § 73.215 which
   have become fully spaced under § 73.207 may file a modification of
   license application to delete the § 73.215 contour protection
   designation with an exhibit to demonstrate that the station is fully
   spaced in accordance with § 73.207. The contour protection designation
   will be removed upon grant of the license application. Applications
   filed under this rule section will be processed on a first come / first
   served basis with respect to conflicting FM commercial minor change
   applications and modification of license applications (including those
   filed pursuant to § 73.1690 (b) and (c)(6) and (c)(7)).

   (7) FM omnidirectional commercial stations, and omnidirectional
   noncommercial educational FM stations operating on Channels 221 through
   300 (except Class D), which are not designated as contour protection
   stations pursuant to § 73.215 and which meet the spacing requirements of
   § 73.207, may file a license modification application to increase ERP to
   the maximum permitted for the station class, provided that any change
   in the height of the antenna radiation center remains in accordance
   with § 73.1690(c)(1). Program test operations may commence at full power
   pursuant to § 73.1620(a)(1). All of the following conditions also must
   be met before a station may apply pursuant to this section:

   (i) The station may not be a “grandfathered” short-spaced station
   authorized pursuant to § 73.213 or short-spaced by a granted waiver of
   § 73.207;

   (ii) If the station is located in or near a radio quiet zone, radio
   coordination zone, or a Commission monitoring station (see § 73.1030 and
   § 0.121(c) of this chapter), the licensee or permittee must have secured
   written concurrence from the affected radio quiet zone, radio
   coordination zone, or the Commission's Public Safety and Homeland
   Security Bureau in the case of a monitoring station, to increase
   effective radiated power PRIOR to implementation. A copy of that
   concurrence must be submitted with the license application to document
   that concurrence has been received;

   (iii) The station does not require international coordination as the
   station does not lie within the border zones, or clearance has been
   obtained from Canada or Mexico for the higher power operation within
   the station's specified domestic class and the station complies with
   § 73.207(b)(2) and (3) with respect to foreign allotments and
   allocations;

   (iv) The increased ERP will not cause the station to violate the
   multiple ownership requirements of § 73.3555.

   (8) FM commercial stations and FM noncommercial educational stations
   may decrease ERP on a modification of license application provided that
   exhibits are included to demonstrate that all five of the following
   requirements are met:

   (i) Commercial FM stations must continue to provide a 70 dBu principal
   community contour over the community of license, as required by
   § 73.315(a). Noncommercial educational FM stations must continue to
   provide a 60 dBu contour over at least a portion of the community of
   license. The 60 and 70 dBu contours must be predicted by use of the
   standard contour prediction method in § 73.313(b), (c), and (d).

   (ii) For commercial FM stations only, there is no change in the
   authorized station class as defined in § 73.211.

   (iii) For commercial FM stations only, the power decrease is not
   necessary to achieve compliance with the multiple ownership rule,
   § 73.3555.

   (iv) Commercial FM stations, noncommercial educational FM stations on
   Channels 221 through 300, and noncommercial educational FM stations on
   Channels 200 through 220 which are located in excess of the distances
   in Table A of § 73.525 with respect to a Channel 6 TV station, may not
   use this rule to decrease the horizontally polarized ERP below the
   value of the vertically polarized ERP.

   (v) Noncommercial educational FM stations on Channels 201 through 220
   which are within the Table A distance separations of § 73.525, or Class
   D stations on Channel 200, may not use the license modification process
   to eliminate an authorized horizontally polarized component in favor of
   vertically polarized-only operation. In addition, noncommercial
   educational stations operating on Channels 201 through 220, or Class D
   stations on Channel 200, which employ separate horizontally and
   vertically polarized antennas mounted at different heights, may not use
   the license modification process to increase or decrease either the
   horizontal ERP or vertical ERP without a construction permit.

   (9) The licensee of an AM, FM, or TV commercial station may propose to
   change from commercial to noncommercial educational on a modification
   of license application, provided that the application contains
   completed Sections II and IV of FCC Form 340. In addition, a
   noncommercial educational AM licensee, a TV licensee on a channel not
   reserved for noncommercial educational use, or an FM licensee on
   Channels 221 to 300 (except Class D FM) on a channel not reserved for
   noncommercial educational use, may apply to change from educational to
   commercial via a modification of license application, and no exhibits
   are required with the application. The change will become effective
   upon grant of the license application.

   (10) Replacement of a transmission line with one of a different type or
   length which changes the transmitter operating power (TPO) from the
   authorized value, but not the ERP, must be reported in a license
   modification application to the Commission.

   (11) Correction of geographic coordinates where the change is 3 seconds
   or fewer in latitude and/or 3 seconds or fewer in longitude, provided
   there is no physical change in location and no other licensed
   parameters are changed. The correction of coordinates may not result in
   any new short spacings or increases in existing short spacings.

   (d) The following changes may be made without authorization from the
   FCC, however informal notification of the changes must be made
   according to the rule sections specified:

   (1) Commencement of remote control operation pursuant to § 73.1400.

   (2) Modification of an AM directional antenna sampling system. See
   § 73.68.

   (e) Any electrical and mechanical modification to authorized
   transmitting equipment that is not otherwise restricted by the
   preceding provisions of this section, may be made without FCC
   notification or authorization. Equipment performance measurements must
   be made within ten days after completing the modifications (See
   § 73.1590). An informal statement, diagram, etc., describing the
   modification must be retained at the transmitter site for as long as
   the equipment is in use.

   [ 47 FR 8590 , Mar. 1, 1982]

   Editorial Note: For Federal Register citations affecting § 73.1690, see
   the List of CFR Sections Affected, which appears in the Finding Aids
   section of the printed volume and at www.govinfo.gov.

   return arrow Back to Top