Phoenix Field Testing Highlights SFN’s Ability To Boost Coverage, Fill Holes
The single frequency network (SFN) capability of next-generation television can help TV broadcasters greatly enhance robust reception of broadcast TV signals, according to a report on the latest field trials of SFN technology recently completed as part of Phoenix Model Market testing.
“Since last summer, we’ve been testing out various configurations with another NextGen TV transmission tower that can greatly enhance reception and make possible new services such as data sent to both cars and homes,” said Anne Schelle, managing director of Pearl TV, which is coordinating the Phoenix Model Market project. “The results are very encouraging.”
The second Phoenix-area NextGen TV station launched last summer from KASW (CW) using a single frequency network to supplement existing signals in the nation’s 11th largest TV market. KASW is owned by E.W. Scripps) and hosts KSAZ (Fox) programming.
Pearl TV Chief Technical Officer Dave Folsom said: “Starting in February, we began a series of tests of the single frequency network broadcast from KASW on physical channel 27. With its primary transmitter about eight miles south of downtown Phoenix and a smaller transmitter on the same physical channel 27 about 18 miles away on Shaw Butte, we were able to determine the impact of how different power levels and polarizations affected reception at various locations around the Phoenix metro area. The robustness of the signal improved. Viewer reception in difficult areas was also improved. Technical coordination between the two transmitters was shown to dramatically enhance what a consumer would be expected to receive.”
“Our two testing transmission antenna patterns were designed to intentionally overlap each other,” Folsom continued. “Their signals are timed (in frequency and time) such as to interfere with each other in a positive or additive fashion and thus improve viewer’s resultant signal level, service margin and receivability within their overlap area. This is the very basis of a single frequency network’s design. The improvement in signal level and service margin translates into a marked improvement in the additive signal’s signal-to-noise component. That means we can either improve reception or increase carriage bandwidth for more data.”
The recent testing was devised to test 40 locations in an approximate grid within the system’s transmission overlap area. An omnidirectional test receiver antenna was purposely used in the testing to ensure the reception was taking full benefit of both transmission signals within the overlap area.
Large improvements in signal level and service margin were found in nearly all test locations when the single frequency network nodes were both transmitting. Error-free reception was improved in approximately 80% of the sites, according to the test report compiled by broadcast engineering consultants Meintel, Sgrignoli & Wallace as part of the Phoenix Model Market testing program.
Schelle said: “We believe that broadcast TV has the potential to offer a new data delivery service, because of television’s new broadcast standard speaks the same language as the internet itself. A single frequency network arrangement with multiple transmission towers can help broadcasters develop new markets and new opportunities.”