Roadstar CLT-700, Руководство по обслуживанию

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1. RX VCO circuit
RX VCO circuit is configured by Q305, Q306, D302 (varicap diode), L301 (air coil), and
some additional passive parts.
The control voltage from pin 14 (charge pump out) of the U302 (PLL IC) is supplied to
the D302 cathode through passive loop filter (C336, C337, C338, R329, R330, R331)
to control the oscillation frequency.
L301 is used to adjust the oscillation frequency band.
The oscillation frequency of 450MHz band signal goes to pin 16 of U302 via C345.
The oscillator output is doubled by Q305 (doubler) and fed into Q303 (RX mixer).
2. TX VCO circuit
TX VCO circuit is configured by Q307, D303, L302 and some additional passive parts.
The control voltage from pin 3 (charge pump out) of the U302 is supplied to the D303
cathode through passive loop filter (C353, C354, C355, R338, R339, R340) to control
the oscillation frequency.
The modulating signal (MOD_AUDIO) is supplied to D303 anode.
L302 is used to adjust the oscillation frequency band.
The oscillation frequency of 450MHz band signal goes to pin 1 of U302 via C363.
The doubled frequency of the 450MHz is taken out from the Q308 (doubler) collector
side and fed to the transmission section of the next stage composed of Q309 (driver
amp) and Q310 (power amp).
The Q307 of VCO and Q308, Q309 is powered through the Q9 by the command of
VCO_CON of the CPU (pin 34).
Q310 is powered through the Q8 by the command of AMP_CON of CPU (pin 35).
3. PLL (phase locked loop) Section
U302 is a dual PLL IC which has two PLL circuits each one for the transmitter and
receiver sections.
Frequency signal of 450MHz band from the VCO is supplied to pins 1 (TX) and pin 16
(RX), and it is divided down to 6.25KHz in accordance with the frequency division ratio
assigned by CPU .
Reference frequency 6.25KHz is made by dividing X301 (21.2503MHz) in accordance
with reference frequency division ratio assigned by CPU.
Voltage of the frequency error comes from pin 3(TX), 14(RX) of U302 as a DC signal.
These voltage are supplied to D303 of the transmitter VCO and D302 of the receiver
VCO and the VCO frequencies are locked to 6,25KHz reference frequency.
The pin 6,7 and 8 of U302 are the serial data inputs for the frequency divider deciding
the division ratio.