http://broadcastengineering.com/RF/analog-shutdown-nears-antenna-reality-eme rges-0609/ As government officials campaign to offer the facts about DTV reception, millions of over-the-air viewers are going to be faced next February with a harsh reality: install a sophisticated new outdoor antenna or subscribe to a pay-TV service. That's because in many parts of the United States, viewers are going to find that reception of digital signals over the air is not so easy. In fact, due to many conditions, it may be impossible even with an antenna. Centris, a market research firm, estimates these issues will affect more than 40 million primary and vacation households and that the government is leaving out two key details in their DTV education campaign. The firm outlined its differences with the government and answered their public criticism in a new DTV Reception Study Fact Sheet. The first detail relates to the type of antenna the government assumes the viewer is using. The assumption is that the TVs are connected to an outdoor antenna 30ft above the ground with an electric motor that allows the user to point the antenna toward the desired station. In its research, Centris found that 75 percent of over-the-air households use indoor antennas on their TVs, and only 13 percent have an outdoor motorized roof-top antenna. In households with indoor antennas, the need for the TV signal to penetrate the premises causes it to be at least between three and 100 times lower in power due to loss. The second important detail is the digital "cliff effect." Today, many viewers watch analog signals that are less than ideal, perhaps with minor impairments of noise, Centris said. However, digital signals exhibit a cliff effect so that unless signals are well above levels that many people consider acceptable for analog, the digital signal will not work at all. Though Centris does validate the government's recommendation for the required outdoor antenna for most households (see www.antennaweb.org <http://www.antennaweb.org/>), it notes that a variety of conditions in individual households will cause about 10 percent of homes to experience problems even if they use the recommended outdoor antenna. Centris predicts that more than half of households are located in challenging digital TV reception areas. Two of the three options currently being promoted by the FCC (acquiring new digital TV sets and purchasing government subsidized digital-analog converter boxes) are entirely dependent on receiving digital TV signals through an antenna. The third option is signing up with a pay service provider.