Circuit Operating Descriptions
7-34
(3) Modulator Section
A. RF Modulator generates, from a baseband video and audio signal, PLL frequency synthesized RF TV channel
signal in VHF band. (3ch = 61.25MHz, 4ch = 67.25MHz)
B. PLL synthesized audio FM (4.5MHz).
C. The 4.43MHz reference frequency for PLL can either be generated internally or input from an external source.
Fig. 7-31 Modulator Section Block Diagram
ANTENNA
TO TUNER SECTION
HIGH CH
OSC
LOW CH
OSC
CH S/W
ANT S/W
VIDEO
OUT
TO TV
AUDIO IN
2
ANT S/W
DRIVER
VIDEO
MOD.
FM
MOD.
AUDIO
CARRIER
MOD.
WHITE
CLIP
VIDEO IN
6
