§  74.706   Digital TV (DTV) station protection.

   (a) For purposes of this section, the DTV station protected service
   area is the geographic-area in which the field strength of the
   station's signal exceeds the noise-limited service levels specified in
   §  73.622(e) of this chapter. The extremity of this area (noise-limited
   perimeter) is calculated from the authorized maximum radiated power
   (without depression angle correction), the horizontal radiation
   pattern, and height above average terrain in the pertinent direction,
   using the signal propagation method specified in §  73.625(b) of this
   chapter.

   (b)(1) An application to construct a new low power TV or TV translator
   station or change the facilities of an existing station will not be
   accepted if it specifies a site which is located within the
   noise-limited service perimeter of a co-channel DTV station.

   (2) Due to the frequency spacing which exists between TV channels 4 and
   5, between Channels 6 and 7, and between Channels 13 and 14, adjacent
   channel protection standards shall not be applicable to these pairs of
   channels.

   (c) The low power TV, TV translator or TV booster station field
   strength is calculated from the proposed effective radiated power (ERP)
   and the antenna height above average terrain (HAAT) in pertinent
   directions.

   (1) For co-channel protection, the field strength is calculated using
   Figure 9a, 10a, or 10c of §  73.699 (F(50,10) charts) of part 73 of this
   chapter.

   (2) For adjacent channel protection, the field strength is calculated
   using Figure 9, 10, or 10b of §  73.699 (F(50,50) charts) of part 73 of
   this chapter.

   (d) A low power TV, TV translator or TV booster station application
   will not be accepted if the ratio in dB of its field strength to that
   of the DTV station (L/D ratio) fails to meet the following:

   (1) −2 dB or less for co-channel operations. This maximum L/D ratio for
   co-channel interference to DTV service is only valid at locations where
   the signal-to-noise (S/N) ratio is 25 dB or greater. At the edge of the
   noise-limited service area, where the S/N ratio is 16 dB, the maximum
   L/D ratio for co-channel interference from analog low power TV, TV
   translator or TV booster service into DTV service is −21 dB. At
   locations where the S/N ratio is greater than 16 dB but less than 25
   dB, the maximum L/D field strength ratios are found from the following
   Table (for values between measured values, linear interpolation can be
   used):
   Signal-to-noise ratio(dB) DTV-to-low power ratio (dB)
   16.00                                           21.00
   16.35                                           19.94
   17.35                                           17.69
   18.35                                           16.44
   19.35                                            7.19
   20.35                                            4.69
   21.35                                            3.69
   22.35                                            2.94
   23.35                                            2.44
   25.00                                            2.00

   (2) + 48 dB for adjacent channel operations at:

   (i) The DTV noise-limited perimeter if a low power TV, TV translator or
   TV booster station is located outside that perimeter.

   (ii) At all points within the DTV noise-limited area if a low power TV
   or TV translator is located within the DTV noise-limited perimeter, as
   demonstrated by the applicant.

   [ 62 FR 26721 , May 14, 1997, as amended at  63 FR 13563 , Mar. 20, 1998;
    64 FR 4327 , Jan. 28, 1999]

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