Whircool- VERY Simplified Explanation
"I wonder why they just didn't start color sets out in that form? Anyone know the answer?"
Whirlcool:
Without getting too technical and involved, it had to do with the way colour images were generated, vs. the way B&W ones were generated.
All CRT televisions work with a picture tube. All picture tubes have an electron gun at the back (in the "neck" of the tube), and phosphors painted on the inside of the tube's "face" (the part of the tube you watch). When electrons from the gun hit the phosphors, they light up, forming the picture you see. But there is one crucial difference between colour and B&W:
B&W tubes have phosphor LINES painted on the inside of the face, and colour tubes have phosphor DOTS painted there. With B&W, each line goes lighter or darker according to the picture info being broadcast to the set, forming the picture. This is easy to do, because lines are continuous(this is highly simplified).
But with colour TV, you can't settle for that, because instead of a phosphor line that is continuous, you have a gazillion little separate dots, EVERY ONE of which must be hit by the electron guns and lighted up, in order to form a picture. There are three phosphor colours- red, yellow and blue-green (cyan), that are used. There is a separate electron gun for each colour phosphor.
Now, since electrons being shot from the guns travel in straight lines, it's easy to see that there is only a narrow angle of travel possible. This is only a minor factor in B&W; it's fairly easy to get the beam into the corners of a rectangular tube. But in colour, you can't easily get the electron beam to travel into corners, and that's what dictated the round colour tubes, because the lack of corners eliminated the problem cheaply and easily. Improvements in the electron gun technology eventually permitted widening the angle, and therefore made getting the electron beam into corners possible.
There is the additional complication of B&W sets having only one electron gun, and colour sets having three, which must work in sync, but that's another story.
Again, this is very simplified, and a visit to Ed Reitan's Colour TV site will help with understanding more about the fabulous NTSC system that has served this nation for 54 years, and which will succumb to politicians' stupidity and corporate greed next February.
Here's a page on B&W TV:
Ever wonder how television works? The technology has been around long enough to seem ordinary, but the box that brings TV shows into your home is an amazing device. How is the picture formed? Where does the color come from? Let's find out!
electronics.howstuffworks.com
And here's a link to Ed Reitan's page on colour, which is highly recommended: