Multitone RPR 563GS, Техническое руководство

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RPR 563GS/KGS
TM1187A Issue C Page 3 - 3
RADIO BOARD
Power Supplies
7. Battery Voltage (B+), TxB+, SPEECH3V and the +4.5V supply lines are derived from
the Decoder Board and are available at PL301.
8. Receiver IF Amplifier IC302 is gated on and off by the Battery Economy Circuit (BEC)
line from the Gate Array on the Decoder Board (via PL301 pin 12). This can be
overridden for manual tests by taking /BEC.EN low. When gated on, TR322 conducts
providing power to pin 20 of IC302, which drives an internal voltage regulator. This in
turn is applied to TR323 to provide a 1V regulated supply rail which powers most of the
receiver. Voltage adjustment is made via RV301.
9. The transmitter oscillator and exciter circuits are powered from an on-board 2.5V
regulator (TxREG) comprising IC301, TR309, TR310 and TR311, and which is powered
from the B+ line. IC301 also supplies a steady bias voltage via R318 to varicap diode
D301.
Receiver
10. A block diagram of the receiver is shown in Figure 1.
11. Receiver antenna AE302/303 is tuned by C339 and C395. Signals from the antenna
are fed to the RF amplifier TR316, TR317. The collector-tuned circuit is used to match
the wideband Surface Acoustic Wave (SAW) filter FL303. Transistor TR315 buffers the
SAW output to the mixer TR318, preventing the SAW filter output affecting the injection
level.
12. The local oscillator comprises TR312, XL303 and associated components. Frequency
adjustment is by C394. Local oscillator frequency is calculated as follows:
fx =
carrier fre 21.4MHz
9
where fx is the crystal frequency in MHz.
13. The collector of TR312 is tuned to the third harmonic of XL303 by C382. TR312 output
is then tripled by TR337 to provide the correct injection frequency for the mixer. The
21.4MHz IF signal is passed by filter FL302, providing further selectivity.
14. The second oscillator runs at 20.945MHz and consists of TR314, XL302 and associated
components. Output from the oscillator is loosely coupled to the second mixer TR313,
where it mixes with FL302 output to form the 2nd IF of 455kHz. Resistor R352 on
TR312 collector provides matching for the 455kHz ceramic filter FL304.