DTV Coverage May Lose Viewers
By Mark Fleischmann February 14, 2008 — Will the differing dispersion patterns of digital television broadcasts affect viewers? Yes, and as many as six million of them may lose reception of some channels, according to a study by Centris, an LA-based market research firm.

Centris estimates that 5.9 million viewers will get fewer channels. That's easily enough to swing a presidential election, though not the coming one. Analog TV broadcasting will end on February 17, 2009, just after the next president takes office.

The basic problem is the cliff effect. When an analog TV signal deteriorates, the picture gets messy. But in digital TV, when the signal gets low enough, the picture can suddenly disappear entirely.

As the research firm explains: "Centris examined several large TV markets and exercised models of coverage to determine how many broadcast stations could be received in zip codes within 5 mile intervals of the TV towers in a 60-75 mile radius corresponding to the FCC-identified service contours. Alarmingly, the results showed that there was little continuous coverage beyond 35 miles."

The percentage of lost viewers depends on the landscape. In the flat terrain of Las Vegas, 2.5 percent of broadcast-dependent viewers would lose at least one of five major networks. In hillier Philly, make that 5 percent. In St. Louis, 10 percent.

Viewers using set-top (as opposed to roof) antennas are more likely to have problems. According to Centris, that would encompass more than three-quarters of broadcast-dependent households.

So even if gramps dutifully takes his $40 federal coupon to Best Buy and comes home with a set-top digital-to-analog TV adapter, his analog set may still show a blank screen when analog TV broadcasting ends in 2009.

Centris also believes the number of households not receiving cable or satellite service is far higher than previously reported by others. It put the number at 117 million, of which 40 million get over-the-air TV. Presumably the remainder are connected to other signal sources such as DVD players.