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Why is "sandstorm" on analog color television black and white, not color, and why does it sometimes appear color?


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Why is "sandstorm" on analog color television black and white, not color, and why does it sometimes appear color?

Analog broadcasting, one of the television broadcasting systems, has been replaced by digital broadcasting mainly in developed countries since the end of the 1990s, and the chance of seeing the appearance has gradually decreased, but the analog TV has a white screen on the screen. Appears in large quantitiessandstormMany people have seen the "" projected. In response to the "sand storm", the question was "Why isn't analog color TV sand storm a color?"Stack ExchangeHas been posted and discussed.

electrical engineering-Why do color TVs make black and white snow?-Engineering Stack Exchange
https://engineering.stackexchange.com/questions/33737/why-do-color-tvs-make-black-and-white-snow

Asked a questionGlorfindelHe said, "I understand that black and white TV sandstorms are black and white, but why are color TV sandstorms not color?" "Do you not decode noise as a color video signal?"

For this questionTransistorAccording to, the TV receiver isHorizontal retrace intervalRequired to correctly reproduce color signalsColor burst signalPut onSubcarrierIt cannot be detected. So the receiverColor killer circuitIs turned on to stop receiving color signals, which explains that black and white noise occurs.

But,Brian N Park"Color sandstorms appeared on color TVs from the 1970s to the 1980s," denied Transistor.

In the absence of a coherent answer,Mike"Even if you do not receive a color signal, a color sandstorm can occur due to physiological and technical aspects." One of the reasons is that the optical illusion is a physiological aspect. When looking at the noise of "sandstorms," ​​it is explained that the human eyes may have an illusion of color even if there is no color on the screen.

Technically, as explained by Transistor, the signals received by the receiver should not contain color signals. Still, the reason that color noise can be displayed on the screen is that the focus of the light rays of the three primary colors may be slightly shifted from the center of the three primary colors. For this reason, Mike comments that certain colors may be visible.

by arnau (BCN)

Also poor qualityAnalog-digital conversion circuitIt is also described that when using, analog signals cannot be converted to "0" and "1" exactly, and color noise may be displayed.

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