Vertex Standard VXR-9000EV Service Manual page 15

TX PLL and VCO Circuits
The transmitter's PLL circuitry consists of PLL subsystem
IC Q1008 (MB15A02PFV1) on the MAIN Unit, which con-
tains a reference oscillator/divider, serial-to-parallel data
latch, programmable divider, phase comparator and a
swallow counter. Stability is obtained by a regulated 5 V
DC supply via Q1062 (L78M05T) and temperature com-
pensated 14.4 MHz crystal oscillator X1001.
The TX VCO consisting of transistor Q1021 (2SC5107)
and varactor diodes D1008 and D1009 (both HVU306)
oscillates between 148 MHz and 174 MHz according to
the programmed transmit frequency. The theory of oper-
ation of the remainder of the PLL circuitry is similar to
that of the RX PLL circuit; however, dividing data from
the Main Q3014 (HD64F2238BFA13) on the CNTL Unit
is such that the VCO frequency is the actual transmit fre-
quency.
APC (Automatic Power Control)
RF power output from the final amplifier module Q7007
(S-AV33) is sampled by C7041 and C7044, then rectified
by D7006 and D7007 (both HSM88AS). The resulting DC
voltage from the Main CPU Q3014 (HD64F2238BFA13)
on the CNTL Unit, to produce a control voltage for the
Automatic Power Controller Q7018 (LM2904PW), which
regulates control voltage of Q7007 (S-AV33).
Circuit Description
CNTL (Control) Unit
The CNTL Unit consists of 8-bit CPU Q3014
(HD64F2238BFA13), EEPROM Q3006 (BR24L32F), RX
and TX speech audio circuits, and various analog switch-
es for the CPU and repeater interconnections.
Microprocessor operational code is stored in Q3006
(BR24L32F), while channel data and repeater configura-
tion information is programmed from an external PC con-
nected to the front panel's MIC jack via a VPL-1 program-
ming cable.
T h e o u t p u t f r o m t h e M a i n C P U Q 3 0 1 4
(HD64F2238BFA13) contains serial control data used for
REPEATER/BASE mode control, as well as TX and RX PLL
data. Crystal X3002 oscillates at 12.288 MHz, and provides
s t a b l e c l o c k t i m i n g f o r t h e M a i n C P U Q 3 0 1 4
(HD64F2238BFA13). When the repeater is powered on,
the voltage at pin 62 of Q3014 (HD64F2238BFA13) be-
comes stable, and the output of voltage detector IC Q3012
(BD4845FVE), which is tied to pin 59 (RST) of Q3014
(HD64F2238BFA13) becomes high, resetting the Main
CPU.
Base Operation (TX, Mic-Input Audio)
Microphone input is delivered past the MIC MUTE switch
Q4002 (DTC323TK), then passes through the audio am-
plifier and active high pass filter at Q4001 (NJM2902V)
when the signal is processed in the same manner as previ-
ously described.
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