Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
Next Page Previous Page

Digital TV / Digital Vs. Analog / Ghosts in the Machine
 

Remember the days before cable television when someone in the family would assume the job of antenna contortionist? To improve that ephemeral picture to a viewable standard, they would skillfully adjust the alignment, length, and altitude of the antenna to get the best possible picture. But sometimes the picture would still show a foggy double image or ghostly images from the next channel. All these problems are caused by the weak signals from distant or blocked transmitters.

Digital signal vs. Analog signal

A basic natural law that our technology can't overcome is the weakening of television signals as they travel away from the transmitter and around or through objects. Both analog and digital signals get weaker with distance. However, while the picture on an analog TV slowly gets worse for more distant receivers, a picture on a digital set will stay perfect until the signal becomes too weak for the receiver to pick it up. By perfect I mean the picture on the TV is exactly the same picture the broadcaster started with at the transmitter. In a digital signal, a one is always a one and a zero is always a zero.

Multi-casting[next]

 

Crash Course Home | Site Map | PBS Digital TV
TV Grows Up | A Different Aspect | The Coming Resolution
Digital Vs. Analog | I Want My Enhanced TV | The Many Faces of HDTV

Copyright © 1998, PBS Online, Inc. All Rights Reserved.
Site Designed and Developed by OPB Learning Media