Vertex Standard VX-4000V, Руководство по обслуживанию

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4-2
Circuit Description
posed of crystal X1001 (14.500 MHz), the temperature
compensation circuit which includes D1033 (
MC2850
) and
thermostats TH1003 and TH1002, and transmit (DCS)
modulation circuit D1029 (
1SV2309
).
Transmitter
Voice audio from the microphone is delivered via the
Mic (Jack) Unit to the MAIN Unit, after passing through
amplifier Q3039/Q2108 (
NJM2902V
), pre-emphasis, lim-
iter (IDC instantaneous deviation control) ,and LPF Q2001
(
NJM2902V
), is adjusted for optimum deviation level and
delivered to the next stage.
Voice input from the microphone and CTCSS are FM-
modulated to the VCO of the synthesizer, while DCS au-
dio is modulated by the reference frequency oscillator of
the synthesizer.
Synthesizer output, after passing through diode switch
D1024 (
1SS321
), is amplified by driver Q1020 / Q1022
(
2SC5415Ex2
) and power module Q1013 (
M67746
) to ob-
tain full RF output. The RF energy then passes through
antenna switch D1007 / D1008 and a low-pass filter cir-
cuit and finally to the antenna connector.
RF output power from the final amplifier is sampled
by CM coupler and is rectified by D1011, D1014
(
HSM88ASx2
). The resulting DC is fed through Automatic
Power Controller Q1007 (
NJM2904V
), Q1001 (
2SC4154E
),
Q1002 (
2SB1143S
) to transmitter RF amplifier and thus
the power output.
Generation of spurious products by the transmitter is
minimized by the fundamental carrier frequency being
equal to the final transmitting frequency, modulated di-
rectly in the transmit VCO. Additional harmonic suppres-
sion is provided by a low-pass filter consisting of L1002,
L1003, L1007, L1012 and C1006, C1009, C1013, C1023,
C1033, C1037 and C1046, resulting in more than 60dB of
harmonic suppression prior to delivery to the RF energy
to the antenna.
DCS Demodulator
DCS signals are demodulated on the MAIN-UNIT, and
are applied to low-pass filter Q2110 (
NJM2902V
), as well
as the limiter comparator Q2110.
CTCSS encoder/decoder
The CTCSS code is generation and encoding by MPU
IC Q2019 (
MB90F583B
).
Demodulation and detection of the CTCSS tones are
carried out by IC Q2013 (
MX165C
).
MPU
Operation is controlled by 16-bit MPU IC Q2019
(
MB90F583B
). The system clock uses a 16.000 MHz crys-
tal for a time base. IC Q2027 (
S-80735SN
) resets the MPU
when the power is on, and monitors the voltage of the
regulated 5V power supply line.
EEPROM
The EEPROM retains TX and RX data for all memory
channels and CTCSS data, DCS data, prescaler dividing,
and REF oscillator data (internal/external).