RELM RM8150 Series, Service Manual

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9
RM8150 SERVICE MANUAL
Transmitting system
Block diagram
ANT SW
D31 D30
RF MAP
RA601317
MIC
AMP
MB15E03 PLL/VCO
CIRCUIT
AUDIO
CONVERTER
AK2346
MIC
AUTO
AGC
TCXO
16.8MHZ
RX/TX
SWD19
½
UPB1509
DIVIDE
R AMP
Q23/Q25
APC
CONTROL
he transmitting circuit directly produces and amplifies the required
frequency and conducts frequency modulation for carrier signals via
the variode.
Transmitting driving power amplifier circuit
ANT
switch
D31 D30
Power
amplifier
RA601317
RX/TX
switch
D19
Drive
amplifier
Q23/Q25
Low-pass
filter
Transmitting signals from the voltage controlled oscillator are amplified
through the frequency division and transmission/receiving selector
diode(D19) and the d riving amp lifier(Q23 and Q25), thus providing the
power moduleRA601317M/(RA554047M) with a special level. The
amplified signals then enter a low-pass filter. The low-pass filter
eliminates unnecessary high-frequency harmonics and the acquired
signals enter the antenna terminal.
Auto power control circuit
The auto transmitting power control (APC) circuit adopts the diodes
(D34, D36) to detect part of the power module outputs and provide
control voltage for U202. Through comparison with the reference
voltage outputted from MCU input, U202 generates the error voltage
and outputs from pin 7 of U202 to control the power amplifier Ra6013
17M and transmits output power stable. The composition of the auto
power cont rol circuit is for preventing over current of the power modul e
due to the fluctuation of the load of the antenna terminal and stabilizing
the output voltage and temperature change of transmission.
Control circuit
The CPU is provided with the following tasks:
1)Embedded Flash Rom, including the control program
2)Controlling the receiving circuit
3)Controlling the transmitting circuit
4)Controlling the display circuit
5)Various function control circuits
6)Communicating data with external devices
Storage circuit
The radio is provided with a 256k-bit EEPROM (U402) for storing pro-
-gramming or testing data.
Display circuit
The display circuit consists of the CPU (U401), the LCD component,
LED and other components. When the communicator is busy and the
LEDG cable is at high level, Q4 is connected and the green LED (D11)
is on. When transmitting, the LEDR cable is at high level, Q8 is conne-
-cted and the red LED (D12) is on, Led D1 to D4 provide the LCD back-
-light, which is on when operating the radio. The LCD is in the *
shape and can display up to 8 digits or letters.
Encoding
CTCSS/DCS:
Outputting CTCSS/DCS signals from the CPU(U401); one channel is
outputted from PIN24 via the low-pass filter and mixed with audio
signals and the external pin DI line, then inputted to the VCO for mod-
-ulation; the other channel is outputted from PIN28 output to TCXO(XI)
for modulation.
2-TONE/5-TONE/DTMF:
PIN2 of the CPU outputs 2-TONE/5-TONE/DTMF coding signals, which
are inputted to the baseband processing IC (U404) via low-pass CR
filter for filtration and deviation control and then sent to the VCO for
modulation.
MSK:
MSK signal is generated by U404, through filtration and frequency
deviation control, it is outputted from PIN7 and sent to VCO for
modulation.
Decoding
CTCSS/DCS
CTCSS/DCS signals are processed and amplified by U403 filter and
sent to PIN92 of MCU for filtration and decoding.
2-TONE/5-TONE
2-TONE/5-TONE signals are filtered and amplified by U503 and receive
waveform transformation via U801 (sine wave into square wave) and
then sent to PIN3 of MCU for filtration and decoding.
DTMF
DTMF signals are filtered and amplified by U503 and sent to PIN2 of
U803 (HT9172) for decoding.
MSK
MSK signal s are filt ered, amplified and decoded by U404 and then s ent
to MCU for MSK signal processing and control.
Power circuit
When the POWER switch on the front panel is pressed, the port
connecting the POWER on the display board and the terminal pins of
the CPU is at low level, Pin 80 (SBC) of the CPU is as high level, Q34
is connected, SB SW (Q42) is connected and supplying power to the
communicator (SB). This circuit is provided with the over-voltage prot-
-ection circuit. If 17V or higher voltage is provided to the power cable,
D839 will be connected and supply voltage to the base of Q38. This
voltage makes Q38 connected and Q34 and SB disconnected.
Chapter 6 Semiconductor Data
Processor: M30620
Pin
1
2
3
4
5
6
7
Port Name
PC/TV
DTMF
HSDI
EEP DAT
EEP CLK
BYTE
CNVSS
In/Out
O
O
I
I/O
O
I
I
Function
Transmit power and receive sensitivity
adjusting voltage output
DTMF/2Tone/5Tone/Beep output
Hi-speed data input
EEPROM data input/ output
EEPROM clock output
GND
GND