Most ghosts are frightening, but the kind that appear on your average television screen can be absolutely exasperating. Double images have been with us for as long as the tube itself.
According to the current issue of Video Magazine, technology under development may banish forever the screen ghosts that haunt even the best TV sets.A ghost is caused by a TV transmission signal being reflected from a tall building, a hill or a body of water. A TV's antenna picks up both the original signal and one or more reflected signals. The set displays them simultaneously. The result is a shadowy duplicate image, slightly displaced from the true image.
Short of moving where there aren't any tall buildings or hills, there's not much to be done about ghosts. Antenna adjustments have little or no effect.
But the National Association of Broadcasters is reviewing proposals for ghost-cancelling systems, and plans to select one as a standard next year.
The proposed systems generally involve a separate tuner that allows the TV to discrimate between the original signal and any reflections. In effect, the TV will ignore the reflections and only project the original signal.
Ghost cancellers built along these lines are already available in Japan for $500 to $1,000. U.S. consumers will probably get a price break thanks to the magic of mass production and the eventual incorporation of the circuits into TV sets. Televisions with these circuits may be available by 1992.
Within a few years, the average ghost canceller will probably only add about $80 to the price of the average set.