Color TV Broadcasting

1. Principle of color TV
At broadcasting station of color tv, subjects are taken pictures in sparated condition into the 3 color primaries by using red, green and blue exlusive cameras. The pictures are camera is received by red picture tube, signal of green camera is received by picture tube,and that of blue is by blue picture tube. Then these 3 picture are piled so that the same image as the subject is reproduced.

2. System of color TV
When color TV is devised, black and white tv receivers have alreardy prevailed widely. So, the following items of compatibility were required.
a. Color tv receiver can receive black and white broadcasting.
b. Black and white tv receivers can receive color broadcasting with black and white picture.
This is called NTSC system, which is standdard system of color tv in Japan. Later, PAL system and SECAM system are develoved in Europa,and are used in many countries as standard.

3. Signal for color TV
Sensitivity of human eyes to red, green and blue is a ratio. So, assuming red mary signal is Er ,green is Eg , and blue is Eb, brightness signal Ey .
Order to make 3 primaries by combining it with brightness sìgnal and apply them to picture tubes, color difference signals, Er-Ey , Eg- Ey , Eb- Ey.

》Er- Ey = 0.70Er- 0.59Eg - 0.11Eb ...
》Eg-Ey =- 0.30Er+0.41Eg- 0.11Eb...
》Eb-Ey = -0.30Er- 0.59Eg+ 0.89Eb...

Accordingly, it only need that these 3 signal of brightness signal Ey and 2 color difference signals, Er- Ey, Eb- Ey are transmitted.These 3 signal are called transmission 3 signal components.

4. How to transmit color TV signal
In color TV, all the sìgnals should be transmitted within the band of 6MHz as well as black and white TV. The brightness signal ( Ey ) is multiplied to two color difference signal ( Er- Ey, Eb- Ey ).
5. Multiplication of crominance signal
The 2 color difference signal is transmitted by carrier of 3.58 MHz called chrominance sub-carrier two-phase modulation method is used for the transmission.That is, Eb-Ey and Er-Ey are applied to a balance modulator, and they are balance modulated separately by color sub carrier with phase difference of 90' then, these 2 are composed to be transmitted as chrominance signal.

6. Multiplication of brightness signal and chrominance sìnal
In order to multiply chrominance signal which has the band within +-0.5MHz of 3.58MHz and brightness signal having the band approximately 4MHz.

7. Composite color TV signal