§  73.626   DTV distributed transmission systems.

   (a) A DTV station may be authorized to operate multiple synchronized
   transmitters on its assigned channel to provide service consistent with
   the requirements of this section. Such operation is called a
   distributed transmission system (DTS). Except as expressly provided in
   this section, DTV stations operating a DTS facility must comply with
   all rules applicable to DTV single-transmitter stations.

   (b) For purposes of compliance with this section, a station's
   “authorized service area” is defined as the area within its predicted
   noise-limited service contour determined using the facilities
   authorized for the station in a license or construction permit for
   non-DTS, single-transmitter-location operation.

   (c) Table of Distances. The following Table of Distances describes (by
   channel and zone) a station's maximum service area that can be obtained
   in applying for a DTS authorization and the maximum interference area
   that can be created by its facilities.

   Table 1 to Paragraph (c)
   Channel Zone Service
   field strength
   (dBu) Distance from reference point Reference
   interference
   field strength
   (dBu) Distance from
   reference point
   F(50,10)
   (km) Node interfering
   field strength
   F(50,10)
   (dBu)
   F(50,90)
   (km) F(50,50)
   (km)
   2-6 1 28 108 132 28 183 18.8
   2-6 2 and 3 28 128 158 28 209 18.8
   7-13 1 36 101 121 33 182 23.8
   7-13 2 and 3 36 123 149 33 208 23.8
   14-36 1, 2, and 3 41 103 142 36 246 26.8

   (1) DTV station zones are defined in § 73.609.

   (2) DTS reference point. A station's DTS reference point is established
   in the FCC Order that created or made final modifications to the
   Post-Transition DTV Table of Allotments, § 73.622(i), and the
   corresponding facilities for the station's channel assignment as set
   forth in that FCC Order.

   (d) Determining DTS coverage. The coverage for each DTS transmitter is
   determined based on the F(50,90) field strength given in the Table of
   Distances (in paragraph (c) of this section), calculated in accordance
   with § 73.625(b). The combined coverage of a DTS station is the logical
   union of the coverage of all DTS transmitters.

   (e) DTS protection from interference. A DTS station must be protected
   from interference in accordance with the criteria specified in § 73.616.
   To determine compliance with the interference protection requirements
   of § 73.616, the population served by a DTS station shall be the
   population within the station's combined coverage contour, excluding
   the population in areas that are outside both the DTV station's
   authorized service area and the Table of Distances area (in paragraph
   (c) of this section). Only population that is predicted to receive
   service by the method described in § 73.622(e)(2) from at least one
   individual DTS transmitter will be considered.

   (f) Applications for DTS. An application proposing use of a DTS will
   not be accepted for filing unless it meets all of the following
   conditions:

   (1) The combined coverage from all of the DTS transmitters covers all
   of the applicant's authorized service area;

   (2) Each DTS transmitter's coverage is contained within either the DTV
   station's Table of Distances area (pursuant to paragraph (c) of this
   section) or its authorized service area, except where such extension of
   coverage beyond the station's authorized service area meets the
   following criteria:

   (i) In no event shall the F(50,50) service contour of any DTS
   transmitter extend beyond that of its reference facility; and

   (ii) In no event shall the F(50,10) node-interfering contour of any DTS
   transmitter, aside from one located at the reference point, extend
   beyond the F(50,10) reference-interfering contour of its reference
   facility; and

   (iii) In no event shall the F(50,10) reference-interfering contour of a
   facility at the reference point extend beyond the F(50,10)
   reference-interfering contour of its reference facility;

   (3) Each DTS transmitter's coverage is contiguous with at least one
   other DTS transmitter's coverage;

   (4) The coverage from one or more DTS transmitter(s) is shown to
   provide principal community coverage as required in § 73.625(a);

   (5) The “combined field strength” of all the DTS transmitters in a
   network does not cause interference to another station in excess of the
   criteria specified in § 73.616, where the combined field strength level
   is determined by a “root-sum-square” calculation, in which the combined
   field strength level at a given location is equal to the square root of
   the sum of the squared field strengths from each transmitter in the DTS
   network at that location.

   (6) Each DTS transmitter must be located within either the DTV
   station's Table of Distances area or its authorized service area.

   (g) All transmitters operating under a single DTS license must follow
   the same digital broadcast television transmission standard.

   [ 73 FR 74063 , Dec. 5, 2008, as amended at  83 FR 5022 , Feb. 2, 2018;  86 FR 21226 , Apr. 22, 2021]