How Everything Works
How Everything Works How Everything Works
 

QUESTIONS AND ANSWERS
 
Question 304

How does the picture get to the TV itself? How does a radio wave make a picture?
The television can reconstruct an image from a series of brightness measurements. It takes these brightness measurement and uses them to control the electron beam as it sweeps across the screen of the picture tube. It paints the picture one dot at a time and then starts over when it has finished. Thus all that the radio wave has to send to the television is a series of brightness measurements and some synchronization information (when to start a horizontal scan and when to start a vertical scan). It uses an AM technique to send the brightness measurements on a radio wave. The transmitter's power varies up and down to indicate brightness just as an AM radio transmitter's power varies up and down to indicate which way to push the speaker cone.
         

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