47 CFR §73.6023

1. (a)Station licensees may operate a commonly owned group of Class A stations with contiguous predicted TV noise-limited contours (pursuant to § 73.619(c)) on a common television channel in a distributed transmission system.
2. (b)A Class A TV 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, Class A stations operating a DTS facility must comply with all rules in this part applicable to Class A single-transmitter stations.
3. (c)For purposes of compliance with this section, a Class A station's “authorized facility” is the facility authorized for the station in a license or construction permit for non-DTS, single-transmitter-location operation. A Class A station's “authorized service area” is defined as the area within its protected contour (described by § 73.6010(c)) as determined using the authorized facility.
4. (d)The protected area for each DTS transmitter is determined based on the F(50,90) field strength given in § 73.6010(c), calculated in accordance with § 73.625(b). The combined protected area of a Class A DTS station is the logical union of the protected areas of all DTS transmitters, that falls within the station's authorized service area as defined in paragraph (c) of this section.
5. (e)The DTS limiting area for each DTS transmitter is determined using the field strength from § 73.6010(c) and the F(50,50) curves.
6. (f)An application proposing use of DTS will not be accepted for filing unless it meets all of the following conditions:
   1. (1)The combined protected area covers all of the applicant's authorized service area;
   2. (2)Each DTS transmitter's Class A DTS limiting contour falls within the authorized facility's Class A DTS limiting contour;
   3. (3)Each DTS transmitter's protected area is contiguous with at least one other DTS transmitter's protected area;
   4. (4)The “combined field strength” of all DTS transmitters in a network does not cause interference to another station in excess of the criteria specified in §§ 73.6017, 73.6018, 73.6019, and 73.6020. The combined field strength at a given location is determined by a “root-sum-square” calculation, in which the combined field strength is equal to the square root of the sum of the squared field strengths from each transmitter in the DTS network at that location; and
   5. (5)Each DTS transmitter must be located within the station's authorized service area.
   6. (6)All DTS transmitters must use the same emission mask. See § 73.6024(d).
7. (g)All transmitters operating under a single Class A DTS license must follow the same digital broadcast television transmission standard.