THOMSON VK231PS, Technical Manual

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91
FM MODULATION
The luminance signal from the main pre-emphasis stage is sent to the FM modulator. The FM
modulator generates a 3.8-MHz frequency for a synchronisation time signal backdrop, and a
4.8-MHz frequency for a 100% white.
The colour rotation signal, applied at 66 of IV001, causes a continuous shift of the luminance
signal leading to a 1/2-Fh shift of alternate tracks at the FM modulator output. This shift
eliminates the coinciding of energy lines of the FM carriers of two adjacent tracks.
Signal Y, FM modulated in this way, is available on IV001 Pin 18.
It then goes through a high-pass filter with a cutoff frequency of 1.5-MHz. This filter eliminates
part of the lower side band of the luminance signal, to avoid any overlap with the chrominance
signal.
The luminance signal is adapted and added to the PAL, SECAM, or MESECAM chrominance
signal.
The signal passes through TV008, and is output at 2 of BV001. It is then sent to the recording
amplifier.
RECORDING AMPLIFIER
The recording amplifier is built into the fixed part of the drum motor.
It receives the following signals:
• BV001 Pin 2: Y FM and chroma to be recorded,
• BV001 Pin 4: synch enabling the AGC acting of the FM level during recording,
• BV001 Pin 5: DFF signal, and selection of Standard Play heads and LP, HA SEL heads.