§  27.60   TV/DTV interference protection criteria.

   Base, fixed, control, and mobile transmitters in the 698-763 MHz,
   775-793 MHz, and 805-806 MHz frequency bands must be operated only in
   accordance with the rules in this section to reduce the potential for
   interference to public reception of the signals of existing TV and DTV
   broadcast stations transmitting on TV Channels 51 through 68.

   (a) D/U ratios. Licensees must choose site locations that are a
   sufficient distance from co-channel and adjacent channel TV and DTV
   stations, and/or must use reduced transmitting power or transmitting
   antenna height such that the following minimum desired
   signal-to-undesired signal ratios (D/U ratios) are met.

   (1) The minimum D/U ratio for co-channel stations is:

   (i) 40 dB at the hypothetical Grade B contour (64 dBµV/m) (88.5
   kilometers (55 miles)) of the TV station;

   (ii) For transmitters operating in the 698-746 MHz frequency band, 23
   dB at the equivalent Grade B contour (41 dBµV/m) (88.5 kilometers (55
   miles)) of the DTV station; or

   (iii) For transmitters operating in the 746-763 MHz, 775-793 MHz, and
   805-806 MHz frequency bands, 17 dB at the equivalent Grade B contour
   (41 dBµV/m) (88.5 kilometers (55 miles)) of the DTV station.

   (2) The minimum D/U ratio for adjacent channel stations is 0 dB at the
   hypothetical Grade B contour (64 dBµV/m) (88.5 kilometers (55 miles))
   of the TV station or −23 dB at the equivalent Grade B contour (41
   dBµV/m) (88.5 kilometers (55 miles)) of the DTV station.

   (b) TV stations and calculation of contours. The methods used to
   calculate TV contours and antenna heights above average terrain are
   given in § §  73.683 and 73.684 of this chapter. Tables to determine the
   necessary minimum distance from the 698-763 MHz, 775-793 MHz, and
   805-806 MHz station to the TV/DTV station, assuming that the TV/DTV
   station has a hypothetical or equivalent Grade B contour of 88.5
   kilometers (55 miles), are located in §  90.309 of this chapter and
   labeled as Tables B, D, and E. Values between those given in the tables
   may be determined by linear interpolation. Distances for station
   parameters greater than those indicated in the tables should be
   calculated in accordance with the required D/U ratios, as provided in
   paragraph (a) of this section. The locations of existing and proposed
   TV/DTV stations during the period of transition from analog to digital
   TV service are given in part 73 of this chapter and in the final
   proceedings of MM Docket No. 87-268.

   (1) Licensees of stations operating within the ERP and HAAT limits of
   §  27.50 must select one of four methods to meet the TV/DTV protection
   requirements, subject to Commission approval:

   (i) Utilize the geographic separation specified in Tables B, D, and E
   of §  90.309 of this chapter, as appropriate;

   (ii) When station parameters are greater than those indicated in the
   tables, calculate geographic separation in accordance with the required
   D/U ratios, as provided in paragraph (a) of this section;

   (iii) Submit an engineering study justifying the proposed separations
   based on the parameters of the land mobile station and the parameters,
   including authorized and/or applied for facilities, of the TV/DTV
   station(s) it is trying to protect; or,

   (iv) Obtain written concurrence from the applicable TV/DTV station(s).
   If this method is chosen, a copy of the agreement must be submitted
   with the application.

   (2) The following is the method for geographic separations. (i) Base
   and fixed stations that operate in the 746-763 MHz, 775-787 MHz, and
   788-793 MHz bands having an antenna height (HAAT) less than 152 m. (500
   ft.) shall afford protection to co-channel and adjacent channel TV/DTV
   stations in accordance with the values specified in Table B (co-channel
   frequencies based on 40 dB protection) and Table E (adjacent channel
   frequencies based on 0 dB protection) in §  90.309 of this chapter. Base
   and fixed stations that operate in the 698-746 MHz band having an
   antenna height (HAAT) less than 152 m. (500 ft.) shall afford
   protection to adjacent channel DTV stations in accordance with the
   values specified in Table E in §  90.309 of this chapter, shall afford
   protection to co-channel DTV stations by providing 23 dB protection to
   such stations' equivalent Grade B contour (41 dBµV/m), and shall afford
   protection to co-channel and adjacent channel TV stations in accordance
   with the values specified in Table B (co-channel frequencies based on
   40 dB protection) and Table E (adjacent channel frequencies based on 0
   dB protection) in §  90.309 of this chapter. For base and fixed stations
   having an antenna height (HAAT) between 152-914 meters (500-3,000 ft.)
   the effective radiated power must be reduced below 1 kilowatt in
   accordance with the values shown in the power reduction graph in Figure
   B in §  90.309 of this chapter. For heights of more than 152 m. (500
   ft.) above average terrain, the distance to the radio path horizon will
   be calculated assuming smooth earth. If the distance so determined
   equals or exceeds the distance to the hypothetical or equivalent Grade
   B contour of a co-channel TV/DTV station ( i.e. , it exceeds the
   distance from the appropriate Table in §  90.309 of this chapter to the
   relevant TV/DTV station), an authorization will not be granted unless
   it can be shown in an engineering study ( see paragraph (b)(1)(iii) of
   this section) that actual terrain considerations are such as to provide
   the desired protection at the actual Grade B contour (64 dBµV/m for TV
   and 41 dBµV/m for DTV stations) or unless the effective radiated power
   will be further reduced so that, assuming free space attenuation, the
   desired protection at the actual Grade B contour (64 dBµV/m for TV and
   41 dBµV/m coverage contour for DTV stations) will be achieved.
   Directions for calculating powers, heights, and reduction curves are
   listed in §  90.309 of this chapter for land mobile stations. Directions
   for calculating coverage contours are listed in §  73.683 through 73.685
   of this chapter for TV stations and in §  73.625 of this chapter for DTV
   stations.

   (ii) Control, fixed, and mobile stations (including portables) that
   operate in the 787-788 MHz and 805-806 MHz bands and control and mobile
   stations (including portables) that operate in the 698-757 MHz, 758-763
   MHz, 776-787 MHz, and 788-793 MHz bands are limited in height and power
   and therefore shall afford protection to co-channel and adjacent
   channel TV/DTV stations in the following manner:

   (A) For control, fixed, and mobile stations (including portables) that
   operate in the 787-788 MHz and 805-806 MHz bands and control and mobile
   stations (including portables) that operate in the 746-757 MHz, 758-763
   MHz, 776-787 MHz, and 788-793 MHz bands, co-channel protection shall be
   afforded in accordance with the values specified in Table D (co-channel
   frequencies based on 40 dB protection for TV stations and 17 dB for DTV
   stations) in §  90.309 of this chapter.

   (B) For control and mobile stations (including portables) that operate
   in the 698-746 MHz band, co-channel protection shall be afforded to TV
   stations in accordance with the values specified in Table D (co-channel
   frequencies based on 40 dB protection) and to DTV stations by providing
   23 dB protection to such stations' equivalent Grade B contour (41
   dBµV/m).

   (C) For control, fixed, and mobile stations (including portables) that
   operate in the 787-788 MHz and 805-806 MHz bands and control and mobile
   stations (including portables) that operate in the 698-757 MHz, 758-763
   MHz, 776-787 MHz, and 788-793 MHz bands, adjacent channel protection
   shall be afforded by providing a minimum distance of 8 kilometers (5
   miles) from all adjacent channel TV/DTV station hypothetical or
   equivalent Grade B contours (adjacent channel frequencies based on 0 dB
   protection for TV stations and −23 dB for DTV stations).

   (D) Since control, fixed, and mobile stations may affect different
   TV/DTV stations than the associated base or fixed station, particular
   care must be taken by applicants/licensees to ensure that all
   appropriate TV/DTV stations are considered ( e.g. , a base station may
   be operating within TV Channel 62 and the mobiles within TV Channel 67,
   in which case TV Channels 61, 62, 63, 66, 67 and 68 must be protected).
   Control, fixed, and mobile stations shall keep a minimum distance of
   96.5 kilometers (60 miles) from all adjacent channel TV/DTV stations.
   Since mobiles and portables are able to move and communicate with each
   other, licensees must determine the areas where the mobiles can and
   cannot roam in order to protect the TV/DTV stations.

   Note to §  27.60: The 88.5 km (55mi) Grade B service contour (64 dBµV/m)
   is based on a hypothetical TV station operating at an effective
   radiated power of one megawatt, a transmitting antenna height above
   average terrain of 610 meters (2000 feet) and the Commission's R-6602
   F(50,50) curves. See §  73.699 of this chapter. Maximum facilities for
   TV stations operating in the UHF band are 5 megawatts effective
   radiated power at an antenna HAAT of 610 meters (2,000 feet). See
   §  73.614 of this chapter. The equivalent contour for DTV stations is
   based on a 41 dBµV/m signal strength and the distance to the F(50,90)
   curve. See §  73.625 of this chapter.

   [ 72 FR 48852 , Aug. 24, 2007]

   return arrow Back to Top