User's Manual

12.8MHZ V C TC X O
The reference oscillator comprises V R 421,C R 2(12.8MHZ)and associated resistors and capacitors.
C R 2 provides the reference oscillator frequency and the temperature compensation that ensures
that the frequency remains stableacross the temperature range(typically± 2.5ppm) C R 2 PIN2
is the modulation port for the two port modulation system used in the DATAR ADIO range of
radios and is DC coupled.The reference oscillator signal direct input to the PLL synthesiser
U401.
F requency adjustment is provided by V R 421
V C O S E C TION
The V C O section produces carrier frequencies during transmit and local oscillator
frequencies During receive.
The V C O section contains one V C O and three outputs.One for producing carrier frequencies
during Transmit and one for producing the local oscillator during receive and the other
Output is for PLL IC (U401)F in.
The V C O section also has R x and TX powerline filters.
R X and TX power line filters.
Transistor T851、T323 is configured as a 5v power supply ripple filter.The filter reduces the
noise on the carrier and local oscillator signals.
TC X O
DC
supply
TX OR R X
V C O
Data
U401
PLL
C harge Pump
Loop F ilter
R F Out