Vertex Standard VX-6000V Service Manual page 17

Transmitter
During transmit, the PLL synthesizer oscillates at
the desired frequency directly, for amplification to
obtain RF power output. During transmission, voice
modulation and CTCSS (or DCS) modulation are
applied to this synthesizer.
Voice audio from the microphone is amplified by
the microphone amplifier Q3039 (NJM2902V) in the
DISPLAY Unit, and then deliver to the MAIN Unit.
The amplified audio is supplied to Q2001
(N J M 2 9 0 2 V ) through the amplifier Q2041
(NJM2902V). Q2001consists of the pre-emphasis,
limiter (IDC instantaneous deviation control), and
low-pass filter; the signal is adjusted for optimum
deviation level and delivered to the next stage.
Voice inputs from the microphone and CTCSS are
FM-modulated at the VCO of the synthesizer, while
DCS audio is modulated by the reference frequency
oscillator of the synthesizer.
Synthesizer output, after passing through diode
switch D1025 (1SS321), is amplified by drivers
Q1031 (2SC5415E) and Q1025 (2SC2954) and power
module Q1017 (early model: M67781H, current mod-
el: RA60H1317M for PA Unit or RA30H1317M1A
for PA-2 Unit) to obtain the required RF drive prior
to delivery to the PA Unit or PA-2 Unit.
In the PA Unit, the RF signal is amplified by par-
allel junction transistors Q6001/Q6002 (early model:
both 2SC5125, current model: both 2SC2782A) and
passes through antenna switching relay RL6001 and
a low-pass filter circuit, and ultimately to the anten-
na connector.
RF output power from the final amplifier is sam-
pled by a CM coupler and is rectified by D6002 and
D6003 (both HSM88AS). The resulting DC is fed
through Automatic Power Controller Q1007
(NJM2902V), Q1002 (2SB1143S: early model only)
to control the gain of the transmitter RF amplifier
and thus regulate the power output.
Generation of spurious products by the transmit-
ter is minimized by the fundamental carrier frequen-
cy being equal to the final transmitting frequency,
modulated directly in the transmit VCO. Additional
harmonic suppression is provided by a low-pass fil-
ter consisting of L6007, L6008, L6009, and C6027,
C6039, C6050, C6040, C6047 and C6041, resulting in
more than 65 dB of harmonic suppression prior to
delivery of the RF energy to the antenna.
VX-6000 VHF Service Manual
Circuit Description
In the PA-2 Unit, the RF signal is amplified by
parallel junction transistors Q9001/Q9002 (both
RD70HVF1) and passes through antenna switching
relay RL9001 and a low-pass filter circuit, and ulti-
mately to the antenna connector.
RF output power from the final amplifier is sam-
pled by a CM coupler and is rectified by D9002 and
D9003 (both HSM88AS). The resulting DC is fed
through Automatic Power Controller Q1007
(NJM2902V) to control the gain of the transmitter
RF amplifier and thus regulate the power output.
Generation of spurious products by the transmit-
ter is minimized by the fundamental carrier frequen-
cy being equal to the final transmitting frequency,
modulated directly in the transmit VCO. Additional
harmonic suppression is provided by a low-pass fil-
ter consisting of L9007, L9008, L9009, and C9027,
C9039, C9050, C9040, C9047 and C9041, resulting in
more than 65 dB of harmonic suppression prior to
delivery of the RF energy to the antenna.
DCS Demodulator
DCS signals are demodulated on the MAIN-
UNIT, and are applied to low-pass filter Q2040
(NJM2902V), as well as the limiter comparator Q2040
(NJM2902V).
CTCSS Encoder/Decoder
The CTCSS code is generated and encoded by
MPU IC Q2025 (MB90F583B). Demodulation and
detection of the CTCSS tones are carried out by IC
Q2017 (MX165C).
MPU
Operation is controlled by 16-bit MPU IC Q2025
(MB90F583B). The system clock uses a 16.000 MHz
crystal for a time base. IC Q2035 (RN5VL35AA) re-
sets 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 mem-
ory channels, as well as CTCSS data, DCS data, pres-
caler dividing, and REF oscillator data (internal/ex-
ternal).
8-2