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With DTV, TV Stations Transmit With Lower Power

The hundreds of news stories about the DTV switch for some reason always left out that TV stations would transmit with only 20% of the power they had used for analog. This was known by the FCC, which assigned WCBS-TV channel 2 New York City and WFSB channel 3 Hartford to the same channel - channnel 33. WCBS and WFSB would never be on the same channel in analog. As channel 2 and 3, they both came in clearly in the Fairfield County town of Stratford, Connecticut and other locations in Connecticut and on Long Island with an outside aerial aimed at Manhattan. The FCC did this while saying TV stations' digital coverage areas would be roughly the same as with analog transmission. Also similarly, Philadelphia and New York City channels were placed on the same channel with DTV. Analog TV bends over hills while digital just stops dead - so in hilly areas like the Naugatuck Valley of Connecticut or in upstate New York or Northwest New Jersey, TV reception over the air may be lost entirely in some spots. And what about West Virginia and Colorado and other Western states? WPVI channel 6 Philadelphia is having major problems with its DTV signal for viewers less than 20 miles from the DTV transmitter, according to Broadcasting & Cable. In the New York City market, viewers as close to Manhattan as Queens and Westchester County report major problems. (New York Radio Message Board )

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With DTV stations transmit at 20% of the power. That means the signals are slightly less than half as strong as they were when transmitting in analog. Take the square root of the multiple of the power increase or decrease, and that will give you the strength. Thus, a station increasing from 250 watts to 1,000 watts will be 2 times as strong, not 4 times as strong, at any given location, since the square root of 4 is 2. So at any given location, where the signal is 2 millivolts (the measure of signal strength) at 250 watts, it will become 4 millivolts with 1,000 watts)