Colour Television: Colour Fundamentals and PAL, NTSC and SECAM Systems
What this domain tests
Colour Television: Colour Fundamentals and PAL, NTSC and SECAM Systems tests additive colour, luminance and chrominance, colour difference signals, colour burst, PAL phase alternation, and system differences.
Core rules
- Additive primaries are red, green, blue; equal RGB gives white. Complementary pairs are red-cyan, green-magenta, blue-yellow.
- Luminance Y=0.30R+0.59G+0.11B for NTSC/PAL coefficients. Colour difference signals include R−Y, G−Y, and B−Y.
- PAL 625/50 uses YUV and phase alternation line-by-line; a one-line delay corrects hue errors. NTSC 525/60 uses YIQ; SECAM uses FM colour subcarriers and line-sequential Db/Dr.
- Colour burst gates the receiver subcarrier oscillator and provides a phase reference.
- Saturation is colour amplitude; hue is phase.
Worked example
If the green channel is missing on a colour CRT, red and blue remain. Red plus blue light makes magenta. The fault is in the green video amplifier, green cathode drive, or green gun, not necessarily the colour decoder. If all colours are wrong but luminance is good, check burst and the subcarrier oscillator.
Traps
Mixing PAL and NTSC line and frame rates is a common error. SECAM is not a phase-alternation system like PAL; it uses FM colour subcarriers. Confusing hue with saturation leads to wrong adjustment. Ignoring colour burst prevents proper decoding. A missing primary does not always mean CRT failure.