§ 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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