In North American digital terrestrial television broadcasting, a distributed transmission system (DTS or DTx) is a form of single-frequency network in which a single broadcast signal is fed via microwave, landline, or communications satellite to multiple synchronized terrestrial radio transmitter sites. The signal is then simultaneously broadcast on the same frequency in different overlapping portions of the same coverage area, effectively combining many small transmitters to generate a broadcast area rivaling that of one large transmitter or to fill gaps in coverage due to terrain or localized obstacles.

While the idea of a single-frequency network of multiple transmitters broadcasting the same programming on the same channel from multiple transmitter sites is not a new concept, the ATSC digital television standard in use in North America was not designed for this mode of operation and was poorly adapted to these applications. The restrictive timing requirements and poor multipath interference handling of early ATSC implementations would have precluded multiple synchronous transmitters on the same frequency at the time of the first wide-scale commercial ATSC deployment in 1998; these restrictions eased somewhat as receiver design advanced in subsequent years. By 2004, technology existed to provide digital television receivers with the means to detect static (not mobile or changing) multipath interference (subject to certain timing constraints) and compensate for its effects on the digital signal.

Tests have been run by various individual broadcasters or broadcast groups, including the Metropolitan Television Alliance (MTVA, a consortium of New York City television stations). A series of initial tests involving four distributed transmission sites and over 100 test measurement sites in NYC and New Jersey were completed in June 2008, along with smaller-scale tests in New York in 2007. The New York market is uniquely problematic for multipath reception due to the large number of man-made obstacles which prevent adequate digital coverage of the entire city from the main broadcast facilities atop the Empire State Building.

To the receiver, a signal from a single-frequency network appears as a single broadcast with strong multipath interference; in the worst case, it is detected as a main signal and a reflection both of equal strength as signals arrive from multiple transmitters to the same intermediate location at slightly different times.

The ATSC standard used for digital television in North America, unlike the DVB-T standard in Europe and other nations, uses 8VSB instead of OFDM—a modulation which allowed a station to transmit at lower peak power levels, but which historically has been far inferior in handling multipath reflections and RF interference.

The first widespread commercial deployment of US ATSC digital television began in 1998, with the first early adopters being stations in the largest markets (including New York City, served by transmitters atop the World Trade Center). Digital receivers of this era, while expensive, were poorly equipped to deal with reflected signals—a severe drawback in urbanized environments. Later generations of receiver design significantly mitigated these limitations; by 2004 technology existed to build receivers capable of detecting and compensating for static multipath interference conditions where a single echo was 10 dB weaker (within a 30 microsecond time difference) or the same strength (the worst case, but within a 12 microsecond range).

If the transmitters could be kept at sufficiently precise synchronization and sufficiently close geographical spacing to operate within these limits, a single-frequency network using the new receiver design would be possible even with the existing North American ATSC digital broadcast standards.

Tests by Pennsylvania State University public educational WPSX-TV (now WPSU-TV) were initially made in 2003 WPSU was in analog a VHF 3 station which serves State College, Pennsylvania from a distant transmitter which must also cover Johnstown and Altoona. As a digital station, WPSU had used a large UHF 15 transmitter at the location of the original low-VHF broadcast tower, leading to localized problems with terrain shielding which interfered with UHF reception in State College itself. Relocation of the main transmitter would have interfered with the station's ability to serve the other two communities. Addition of a small (50 kW) synchronized digital TV transmitter in State College, on the same frequency as the main UHF 15 signal, proved a means to improve reception; further improvements would be possible by adding small co-channel 50kW transmitters in each community to be served.