Figure 8-12.--The color camera unit.

Figure 8-12.--The color camera unit.

channel frequency. Modulating the subcarrier makes it

each of the primary colors). Filters and mirrors are

possible to broadcast the color information of the I and

used to direct the right color of light to its respective

Q signals simultaneously without loss of identity. Each

pickup tube. The output of the camera unit provides a

can be recovered as a separate signal with the proper

red, green, and blue video signal to the matrix system

timing of the transmitter and the receiver. The combined

(a circuit that proportions the primary signals to

outputs are designated as the chrominance C signal and

produce the correct brightness and chrominance

are routed to the adder (fig, 8-12).

colors). The three primary colors are identified as R

for red, G for green, and B for blue.

The chrominance C signal (the color information)

and the Y signal (the luminance information) are both

The matrix section is essentially a resistive

coupled to the adder section, or colorplexer. The

voltage divider circuit that proportions the primary

colorplexer combines the Y and C signals, forming the

color signals to produce the brightness and

total video S signal which is sent to the transmitter.

chrominance signals. With the red, green, and blue

color video voltages as inputs, the three video signal

RECEPTION

output combinations formed are the following:

Luminance signal, designated the Y signal,

The received signals of video and sound enter the

which contains the brightness variations of the

receiver/monitor just as they do in black-and-white

picture information.

reception. The same tuner and IF amplifiers are used

(fig. 8-13). In the video amplifier the signals separate.

A color video signal, designated the Q signal,

which corresponds to either green or purple

picture information.

A color video signal, designated the I signal,

which corresponds to either orange or cyan

picture information.

The I and Q signals together contain the color

information for the chrominance (hue and saturation)

signal.

The I and Q signals are transmitted to the receiver

as the sidebands of a 3.58-MHz subcarrier wave (fig.

8-12). A subcarrier wave is a relatively low-frequency

carrier wave that modulates the main carrier wave. The

Figure 8-13.--Color TV receiver, block diagram.

subcarrier frequency remains the same regardless of the

8-15