Vertex Standard EVX-S24, Руководство по обслуживанию

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EVX-S24 UHF Digital/Analog Transceiver Service Manual 8
Circuit Description
1. Receiver System
1-1. Front-end RF Amplifi er
Incoming RF signal from the antenna passes through the
low-pass filter, antenna switching diode
D1011/D1014
(both 1SS390 ), and band-pass fi lter.
The fi ltered RF signal is applied to the amplifi er Q1033
(
MAXT
), then remove the undesired frequen-
cies by another band-pass fi lter.
The amplified RF signal is applied to the custom IC
Q1046 (
RODINIA
).
1-2. Demodulator
The custom IC Q1046 (
RODINIA
) converts a Base Band
signal by mixing the RF signal with the local signal, and
then the Base Band signal is demodulated by the another
section of the custom IC
Q1046 ( RODINIA ).
The local signal is generated by the VCO which consists
of
Q1036 (
BFR460L3
) and varactor diodes D1029/
D1030/D1031/D1032 (all 1SV279 ).
1-3. Audio Amplifi er
The demodulated signal is adjusted the audio volume
level in the custom IC
Q1046 (
RODINIA
). The adjusted
the audio signal is applied to the audio amplifi er Q1040
(
SA58637BS
). As a result, the audio signal provides up
to 500 mW (@4-ohm BTL) for internal speaker and exter-
nal speaker.
2. Transmitter System
2-1. MIC Amplifi er & Modulator
The speech signal from internal microphone MC2001 on
the DISPLAY Unit or external microphone J1005 on the
MAIN Unit is supplied to the custom IC Q1046 (
RO-
DINIA ), which modulates the speech signal to the FM or
digital signal.
2-2. Drive & Final Amplifi er Stages
The modulated signal from the custom IC Q1046 (
RO-
DINIA ) is buffered by Q1034 ( 2SK3077 ) and amplified
by driver amplifi er Q1026 (
RD01MUS2B
). The low level
transmit signal is then applied to Q1016 ( RD04LUS2 ) for
fi nal amplifi cation up to 3 watts output power.
The transmit signal then passes through the antenna
switch
D1009/D1053 (both RN142S ) and is low-pass fi l-
tered to suppress away harmonic spurious radiation before
delivery to the antenna.
2-3. Automatic Transmit Power Control
The current detector Q1006-1 ( AD8566ARM ) detects the
current of the fi nal amplifi er Q1016 (
RD04LUS2
) and the
driver amplifi er Q1026 ( RD01MUS2B ), and converts the
current difference to the voltage difference.
T h e o u t p u t f r o m t h e c u r r e n t d e t e c t o r Q 1 0 0 6 - 1
( AD8566ARM ) is compared with the reference voltage
and amplified by the power control amplifier Q1006-2
( AD8566ARM ).
The output from the power control amplifier Q1006-2
(
AD8566ARM
) controls the gate bias of the driver ampli-
fi er Q1026 ( RD01MUS2B ) and the fi nal amplifi er Q1016
(
RD04LUS2
).
The reference voltage changes into two values (Transmit
Power High and Low) controlled by custom IC
Q1046
(
RODINIA
).
3. PLL Frequency Synthesizer
The frequency synthesizer consists of VCO, TCXO
X1001 , and the custom IC Q1046 ( RODINIA ).
The output frequency from TCXO X1001 is 19.2 MHz
and the tolerance is ±1.5 ppm in the temperature range
–22 °F to +140 °F (–30 °C to +60 °C).
3-1. VCO (Voltage Controlled Oscillator)
The VCO Q1036 ( BFR460L3 ) generates a between 806-
940 MHz. The output from VCO Q1036 (
BFR460L3
) is
amplifi ed by buffer amplifi er Q1041 ( 2SC5010 ) and then
is supplied to the custom IC Q1046 (
RODINIA
).
The VCO frequency is divided into two by the dividing
section of the custom IC
Q1046 ( RODINIA ) in order to
become a true receiving or transmitting frequency.
In the reception, the RF signal convert a Base Band signal
by mixing with the divided VCO signal, and then supplied
to the demodulator section of the custom IC
Q1046 (
RO-
DINIA ), described previously.
In the transmission, the divide VCO frequency is modu-
lated to the FM (or digital) in the custom IC
Q1046 ( RO-
DINIA ), and then is supplied to the transmitter section
described previously.
3-2. Varactor Control Voltage
The tuning voltage (VCV) of the VCO establishes the
lock range of VCO by controlling the cathode of varactor
diode
D1029 , D1030 , D1031 and D1032 (all 1SV279 ).
from the custom IC Q1046 ( RODINIA ).
3-3. PLL
The main constitution product of the PLL is equipped all
with in the custom IC
Q1046 ( RODINIA ), so that all pro-
cessing regarding the frequency control is performed in
the custom IC
Q1046 ( RODINIA ).