Vertex VX-230 Series Service Manual page 7

Circuit Description
3-2. Drive and Final amplifier
The modulated signal from the VCO Q1032 (2SC4227) is buff-
ered by Q1027 (2SC5005). Then the signal is buffered by
Q1018 (2SC5227) for the final amplifier driver Q1015
(RQA0004PXDQS). The low-level transmit signal is then
applied to Q1010 (RQA0011DNS) for final amplification up
to 5watts output power.
The transmit signal then passes through the antenna switch
D1002 (RLS135) and is low pass filtered to suppress away
harmonic spurious radiation before delivery to the antenna.
3-3. Automatic Transmit Power Control
The current detector Q1052-1 (NJM12904R) detects the cur-
rent of Q1010 and Q1015, and converts the current difference
to the voltage difference.
The output from the current detector Q1052-1 is compared with
the reference voltage and amplified by the power control am-
plifier Q1052-2.
The output from Q1052-2 controls the gate bias of the final
amplifiers Q1010 and the final amplifier driver Q1015.
The reference voltage changes into four values (Transmit Pow-
er High and Low) controlled by Q1012 (M62364FP-CH8).
4. PLL Frequency Synthesizer
The frequency synthesizer consists of PLL IC, Q1042
(MB15E03SL), VCO, TCXO (X1002) and buffer amplifier.
The output frequency from TCXO is 16.8MHz and the toler-
ance is ±2.5 ppm (in the temperature range -30 to +60 degrees).
4-1. VCO
While the radio is receiving, the RX oscillator Q1030 (2SK508)
in VCO generates a programmed frequency between 201.65
and 241.65MHz as 1st local signal.
While the radio is transmitting, the TX oscillator Q1032
(2SC4227) in VCO generates a frequency between 134 and
174MHz.
The output from oscillator is amplified by buffer amplifier
Q1027 (2SC5005) and becomes output of VCO. The output
from VCO is divided, one is amplified by Q1027 and feed back
to the PLL IC 8pin. It is put into the mixer as the 1st local signal
through D1012, in transmission, it is buffered Q1018, and more
amplified in Q1015 through D1012 and it is put into the final
amplifier Q1010.
4-2. VCO Tuning Voltage
Tuning voltage of VCO is expanding the lock range of VCO by
controlling the cathode of varactor diode at the voltage and the
control voltage from PLL IC.
VX-230 Series VHF FM Transceiver Service Manual
4-3. PLL
The PLL IC consists of reference divider, main divider, phase
detector, charge pumps and pulse swallow operation. The ref-
erence frequency from TCXO is inputted to 1pin of PLL IC
and is divided by reference divider.
The other hand, inputted feed back signal to 8pin of PLL IC
from VCO is divided with the dividing ratio which becomes
same frequency as the output of reference divider. These two
signals are compared by phase detector, the phase difference
pulse is generated.
The phase difference pulse and the pulse from through the charge
pumps and LPF. It becomes the DC voltage to control the VCO.
The oscillation frequency of VCO is locked by the control of
this DC voltage.
The PLL serial data from CPU is sent with three lines of SDO
(60pin), SCK (58pin) and PSTB (59pin).
The lock condition of PLL is output from the UL (14Pin) ter-
minal and UL becomes "H" at the time of the lock condition
and becomes "L" at the time of the unlocked condition. The
CPU always watches over the UL condition, and when it be-
comes "L" unlocked condition, the CPU prohibits transmitting
and receiving.
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