Subject :- Television Engineering

Topic :- Color TV

Difficulty :- High

• The weighted (B – Y) and (R – Y) signals are modulated without being given a phase shift of 33° as is done in the NTSC system.
• On modulation both the colour difference quadrature signals are allowed the same bandwidth of about 1.3 MHz. This results in better colour reproduction.
• The colour subcarrier frequency is chosen to be 4.43 MHz. It is an odd multiple of one-quarter of the line frequency instead of the half-line offset as used in the NTSC system. This results in somewhat better cancellation of the dot pattern interference.

• The PAL system derives its name, phase alteration by line (i.e., PAL), from this mode of modulation. This technique of modulation cancels hue errors which result from unequal phase shifts in the transmitted signal.

  Where: U = 0.493 (B – Y) and V = 0.877 (R – Y).

                                   C_PAL=√(U^2+V^2 )
  

• The switching action naturally occurs during the line blanking interval to avoid any visible disturbance.