Goto Section: 73.515 | 73.558 | Table of Contents

FCC 73.525
Revised as of November 27, 2020
Goto Year:2020 | 2022
  §  73.525   TV Channel 6 protection.

   The provisions of this section apply to all applications for
   construction permits for new or modified facilities for a NCE-FM
   station on Channels 200-220 unless the application is accompanied by a
   written agreement between the NCE-FM applicant and each affected TV
   Channel 6 broadcast station concurring with the proposed NCE-FM
   facilities.

   (a) Affected TV Channel 6 station. (1) An affected TV Channel 6 station
   is a TV broadcast station which is authorized to operate on Channel 6
   that is located within the following distances of a NCE-FM station
   operating on Channels 201-220:

   Table A
   NCE-FM channel Distance (kilometers) NCE-FM channel Distance
   (kilometers)
   201 265 211 196
   202 257 212 195
   203 246 213 193
   204 235 214 187
   205 225 215 180
   206 211 216 177
   207 196 217 174
   208 196 218 166
   209 196 219 159
   210 196 220 154

   (2) Where a NCE-FM application has been accepted for filing or granted,
   the subsequent acceptance of an application filed by a relevant TV
   Channel 6 station will not require revision of the pending NCE-FM
   application or the FM station's authorized facilities, unless the
   provisions of paragraph (e)(3) of this section for TV translator or
   satellite stations apply.

   (b) Existing NCE-FM stations. (1) A NCE-FM station license authorized
   to operate on channels 201-220 as of December 31, 1984, or a permittee,
   granted a construction permit for a NCE-FM station as of December 31,
   1984, are not subject to this section unless they propose either:

   (i) To make changes in operating facilities or location which will
   increase predicted interference as calculated under paragraph (e) of
   this section to TV Channel 6 reception in any direction; or,

   (ii) To increase its ratio of vertically polarized to horizontally
   polarized transmissions.

   (2) Applicants must comply with the provision of paragraphs (c) or (d)
   of this section unless the application for modification demonstrates
   that, for each person predicted to receive new interference as a result
   of the change, existing predicted interference to two person will be
   eliminated. Persons predicted to receive new interference are those
   located outside the area predicted to receive interference from the
   station's currently authorized facilities (“existing predicted
   interference area”) but within the area predicted to receive
   interference from the proposed facilities (“proposed predicted
   interference area”). Persons for whom predicted interference will be
   eliminated are those located within the existing predicted interference
   area and outside the proposed predicted interference area.

   (i) In making this calculation, the provisions contained at paragraph
   (e) will be used except as modified by paragraph (b)(3) of this
   section.

   (ii) The following adjustment to the population calculation may be
   made: up to 1,000 persons may be subtracted from the population
   predicted to receive new interference if, for each person substracted,
   the applicant effectively installs two filters within 90 days after
   commencing program tests with the proposed facilities and, no later
   than 45 days thereafter, provides the affected TV Channel 6 station (as
   defined in paragraph (a) of this section) with a certification
   containing sufficient information to permit verification of such
   installation. The required number of filters will be installed on
   television receivers located within the predicted interference area;
   provided that half of the installations are within the area predicted
   to receive new interference.

   (3) Where an NCE-FM applicant wishes to operate with facilities in
   excess of that permitted under the provisions of paragraphs (c) or (d)
   of this section, by proposing to use vertically polarized transmissions
   only, or to increase its ratio of vertically to horizontally polarized
   transmissions, the affected TV Channel 6 station must be given an
   option to pay for the required antenna and, if it takes that option,
   the NCE-FM vertically polarized component of power will be one half (−3
   dB) that which would be allowed by the provisions of paragraph (e)(4)
   of this section.

   (4) Applications for modification will include a certification that the
   applicant has given early written notice of the proposed modification
   to all affected TV Channel 6 stations (as defined in paragraph (a) of
   this section).

   (5) Where the NCE-FM station demonstrates in its application that it
   must make an involuntary modification (e.g., due to loss of its
   transmitter site) that would not otherwise be permitted under this
   section, its application will be considered on a case-by-case basis. In
   such cases, the provisions of paragaph (b)(3) of this section do not
   apply.

   (c) New NCE-FM stations. Except as provided for by paragraph (d) of
   this section, applicants for NCE-FM stations proposing to operate on
   Channels 201-220 must submit a showing indicating that the predicted
   interference area resulting from the proposed facility contains no more
   than 3,000 persons.

   (1) In making these calculations, the provisions in paragraph (e) of
   this section will be used.

   (2) The following adjustment to population may be made: up to 1,000
   persons may be subtracted from the population within the predicted
   interference area if, for each person subtracted, the applicant
   effectively installs one filter within 90 days after commencing program
   tests and, no later than 45 days thereafter, provides the affected TV
   Channel 6 station with a certification containing sufficient
   information to permit verification of such installation. The required
   number of filters will be installed on television receivers located
   within the predicted interference area.

   (d) Collocated stations. As an alternative to the provisions contained
   in paragraphs (b) and (c) of this section, an application for a NCE-FM
   station operating on Channels 201-220 and located at 0.4 kilometer
   (approximately 0.25 mile) or less from a TV Channel 6 station will be
   accepted under the following requirements:

   (1) The effective radiated power cannot exceed the following values:

   Table B
   NCE-FM channel Power (kilowatt) NCE-FM channel Power (kilowatt)
              201              1.1            211             26.3
              202              1.9            212             31.6
              203              3.1            213             38.0
              204              5.0            214             46.8
              205              8.3            215             56.2
              206             10.0            216             67.6
              207             12.0            217             83.2
              208             14.8            218            100.0
              209             17.8            219            100.0
              210             21.4            220            100.0

   (2) The NCE-FM application will include a certification that the
   applicant has coordinated its antenna with the affected TV station by
   employing either: The same number of antenna bays with radiation
   centers separated by no more than 30 meters (approximately 100 feet)
   verticially; or, the FM vertical pattern not exceeding the TV vertical
   pattern by more than 2dB.

   (e) Calculation of predicted interference area and population.
   Predictions of interference required under this section and
   calculations to determine the number of persons within a predicted
   interference area for NCE-FM operation on Channels 201-220 are made as
   follows:

   (1) The predicted interference area will be calculated as follows:

   (i) The distances to the TV Channel 6 field strength contours will be
   predicted according to the procedures specified in § 73.684, “Prediction
   of coverage,” using the F(50,50) curves in Figure 9, § 73.699.

   (ii) For each TV Channel 6 field strength contour, there will be an
   associated F(50,10) FM interference contour, the value of which (in
   units of dBu) is defined as the sum of the TV Channel 6 field strength
   (in dBu) and the appropriate undesired-to-desired (U/D) signal ratio
   (in dB) obtained from Figures 1 and 2, § 73.599, corresponding to the
   channel of the NCE-FM applicant and the appropriate F(50,50) field
   strength contour of the TV Channel 6 station.

   (iii) An adjustment of 6 dB for television receiving antenna
   directivity will be added to each NCE-FM interference contour at all
   points outside the Grade A field strength contour (§ 73.683) of the TV
   Channel 6 station and within an arc defined by the range of angles, of
   which the FM transmitter site is the vertex, from 110° relative to the
   azimuth from the FM transmitter site to the TV Channel 6 transmitter
   site, counterclockwise to 250° relative to that azimuth. At all points
   at and within the Grade A field strength contour of the TV Channel 6
   station, the 6 dB adjustment is applicable over the range of angles
   from 70° clockwise to 110° and from 250° clockwise to 290°.

   (iv) The distances to the applicable NCE-FM interference contours will
   be predicted according to the procedures specified in § 73.313,
   “Prediction of Coverage,” using the proposed antenna height and
   horizontally polarized, or the horizontal equivalent of the vertically
   polarized, effective radiated power in the pertinent direction and the
   F(50,10) field strength curves (Figure 1a, § 73.333).

   (v) The predicted interference area will be defined as the area within
   the TV Channel 6 station's 47 dBu field strength contour that is
   bounded by the locus of intersections of a series of TV Channel 6 field
   strength contours and the applicable NCE-FM interference contours.

   (vi) In cases where the terrain in one or more directions departs
   widely from the surrounding terrain average (for example, an
   intervening mountain), a supplemental showing may be made. Such
   supplemental showings must describe the procedure used and should
   include sample calculations. The application must also include maps
   indicating the predicted interference area for both the regular method
   and the supplemental method.

   (vii) In cases where the predicted interference area to Channel 6
   television from a noncommercial educational FM station will be located
   within the 90 dBu F(50,50) contour of the television Channel 6 station,
   the location of the FM interfering contour must be determined using the
   assumption that the Channel 6 field strength remains constant at 90 dBu
   everywhere within the 90 dBu TV contour. The FM to Channel 6 U/D signal
   strength ratio specified in § 73.599 corresponding to the Channel 6 TV
   field strength of 90 dBu shall be used.

   (2) The number of persons contained within the predicted interference
   area will be based on data contained in the most recently published
   U.S. Census of Population and will be determined by plotting the
   predicted interference area on a County Subdivision Map of the state
   published for the Census, and totalling the number of persons in each
   County Subdivision (such as, Minor Civil Division (MCD), Census County
   Division (CCD), or equivalent areas) contained within the predicted
   interference area. Where only a portion of County Subdivision is
   contained within the interference area:

   (i) The population of all incorporated places or Census designated
   places will be subtracted from the County Subdivision population;

   (ii) Uniform distribution of the remaining population over the
   remaining area of the County Subdivision will be assumed in determining
   the number of persons within the predicted interference area in
   proportion to the share of the remaining area of the County Subdivision
   that lies within the predicted interference area; and,

   (iii) The population of the incorporated places or Census designated
   places contained within the predicted interference area will then be
   added to the total, again assuming uniform distribution of the
   population within the area of each place and adding a share of the
   population proportional to the share of the area if only a portion of
   such a place is within the predicted interference area.

   (iv) At the option of either the NCE-FM applicant or an affected TV
   Channel 6 station which provides the appropriate analysis, more
   detailed population data may be used.

   (3) Adjustments to the population calculated pursuant to paragraph
   (e)(2) of this section may be made as follows:

   (i) If any part of the predicted interference area is within the Grade
   A field strength contour (§ 73.683) of a TV translator station carrying
   the affected TV Channel 6 station, the number of persons within that
   overlap area will be subtracted, provided the NCE-FM construction
   permit and license will contain the following conditions:

   (A) When the TV translator station ceases to carry the affected TV
   Channel 6 station's service and the cessation is not the choice of the
   affected TV Channel 6 station, the NCE-FM station will modify its
   facilities, within a reasonable transition period, to meet the
   requirements of this section which would have applied if no adjustment
   to population for translator service had been made in its application.

   (B) The transition period may not exceed 1 year from the date the
   NCE-FM station is notified by the TV Channel 6 station that the
   translator station will cease to carry the affected TV Channel 6
   station's service or 6 months after the translator station ceases to
   carry the affected TV Channel 6 station's service, whichever is
   earlier.

   (ii) If any part of the interference area is within the Grade B field
   strength contour (§ 73.683) of a satellite station of the affected TV
   Channel 6 station, the number of persons within the overlap area will
   be subtracted, provided the NCE-FM permit and license will contain the
   following conditions:

   (A) If the satellite station ceases to carry the affected TV Channel 6
   station's service and the cessation is not the choice of the affected
   TV Channel 6 station, the NCE-FM station will modify its facilities,
   within a reasonable transition period, to meet the requirements of this
   rule which would have applied if no adjustment to population for
   satellite station service had been made in its application.

   (B) The transition period may not exceed 1 year from the date the
   NCE-FM station is notified by the TV Channel 6 station that the
   satellite station will cease to carry the affected TV Channel 6
   stations's service or 6 months after the satellite station ceases to
   carry the affected TV Channel 6 station's service, whichever is
   earlier.

   (iii) If any part of the predicted interference area is located outside
   the affected TV Channel 6 station's Area of Dominant Influence (ADI),
   outside the Grade A field strength contour (§ 73.683), and within the
   predicted city grade field strength contour (73.685(a)) of a TV
   broadcast station whose only network affiliation is the same as the
   only network affiliation of the affected TV Channel 6 station, the
   number of persons within that part will be subtracted. (For purposes of
   this provision, a network is defined as ABC, CBS, NBC, or their
   successors.) In addition, the ADI of an affected TV Channel 6 station
   and the program network affiliations of all relevant TV broadcast
   stations will be assumed to be as they were on the filing date of the
   NCE-FM application or June 1, 1985, whichever is later.

   (iv) In calculating the population within the predicted interference
   area, an exception will be permitted upon a showing (e.g., as survey of
   actual television reception) that the number of persons within the
   predicted interference area should be reduced to account for persons
   actually experiencing co-channel or adjacent channel interference to
   reception of the affected TV Channel 6 station. The area within which
   such a showing may be made will be limited to the area calculated as
   follows:

   (A) The distances to the field strength contours of the affected TV
   Channel 6 station will be predicted according to the procedures
   specified in § 73.684, “Prediction of coverage,” using the F(50,50)
   curves in Figure 9, § 73.699.

   (B) For each field strength contour of the affected TV Channel 6
   station, there will be an associated co-channel or adjacent channel TV
   broadcast station interference contour, the value of which (in units of
   dBu) is defined as the sum of the affected TV Channel 6 station's field
   strength (in dBu) and the appropriate undesired-to-desired signal ratio
   (in dB) as follows:

   Co-channel, normal offset, −22 dB

   Co-channel, no offset, −39 dB

   Adjacent channel, + 12 dB

   (C) The distances to the associated co-channel or adjacent channel TV
   broadcast station interference contour will be predicted according to
   the procedures specified in § 73.684, “Prediction of coverage,” using
   the F(50,10) curves in Figure 9a, § 73.699.

   (D) The area within which the showing of actual interference may be
   made will be the area bounded by the locus of intersections of a series
   of the affected TV Channel 6 station's field strength contours and the
   associated interference contours of the co-channel or adjacent channel
   TV broadcast station.

   (4) The maximum permissible effective radiated power (ERP) and antenna
   height may be adjusted for vertical polarity as follows:

   (i) If the applicant chooses to use vertically polarized transmissions
   only, the maximum permissible vertically polarized ERP will be the
   maximum horizontally polarized ERP permissible at the same proposed
   antenna height, calculated without the adjustment for television
   receiving antenna directivity specified in paragraph (e)(1)(iii) of
   this section, multiplied by either: 40 if the predicted interference
   area lies entirely outside the limits of a city of 50,000 persons or
   more; or 10 if it does not.

   (ii) If the applicant chooses to use mixed polarity, the permissible
   ERP is as follows:

   [H + (V/A)] is no greater than P

   Where:

   H is the horizontally polarized ERP in kilowatts for mixed polarity;

   V is the vertically polarized ERP in kilowatts for mixed polarity;

   A is 40 if the predicted interference area lies entirely outside the
   limits of a city of 50,000 persons or more, or 10 if it does not; and

   P is the maximum permitted horizontally polarized-only power in
   kilowatts.

   (f) Channel 200 Applications. No application for use of NCE-FM Channel
   200 will be accepted if the requested facility would cause
   objectionable interference to TV Channel 6 operations. Such
   objectionable interference will be considered to exist whenever the 15
   dBu contour based on the F(50,10) curves in § 73.333 Figure 1a would
   overlap the 40 dBu contour based on the F(50,50) curves in § 73.699,
   Figure 9.

   [ 50 FR 27963 , July 9, 1985;  50 FR 30187 , July 24, 1985;  50 FR 31379 ,
   Aug. 2, 1985, as amended at  51 FR 26250 , July 22, 1986;  52 FR 25867 ,
   July 9, 1987;  62 FR 51059 , Sept. 30, 1997]

   


Goto Section: 73.515 | 73.558

Goto Year: 2020 | 2022
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