HYT TM-600 User manual

81 30 M6 00 00 01 0
20 08 -03-05

TM-600 SERVICE MANUAL
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CONTENTS
Revision History-----------------------------------------------------------------------------------------------2
General-----------------------------------------------------------------------------------------------------------2
Radio Overview------------------------------------------------------------------------------------------------4
Software Specification--------------------------------------------------------------------------------------6
Circuit Description------------------------------------------------------------------------------------------15
Semiconductor Data----------------------------------------------------------------------------------------20
Component Description-----------------------------------------------------------------------------------24
Parts List 1-----------------------------------------------------------------------------------------------------25
Tuning Description------------------------------------------------------------------------------------------63
Terminal Function-------------------------------------------------------------------------------------------75
Trouble-shooting Flow Chart ---------------------------------------------------------------------------78
Disassembly and Assembly for Repair---------------------------------------------------------------82
Exploded View------------------------------------------------------------------------------------------------85
Parts List 2-----------------------------------------------------------------------------------------------------86
Packing---------------------------------------------------------------------------------------------------------87
PCB View-------------------------------------------------------------------------------------------------------88
Block Diagram------------------------------------------------------------------------------------------------95
Schematic Diagram-----------------------------------------------------------------------------------------96
Specifications-----------------------------------------------------------------------------------------------108

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Revision History
Version Date Contents Revised
8130M60000000 March, 2007 Initial release
8130M60000010 March, 2008 Circuit Update: 1.Add new frequency(470-520MHz 350-400MHz
440-470MHz).
2.update content of tuning description, parts list 1, schematic
diagram and PCB view.
3.Add the new definition for J503 (second development interface)
in Semiconductor Data.
Structure Update: 4.Update Parts list 2 and exploded view.
Software Update: 5. add function keys, tuning items and
initialization data table of different models.
General
Manual Scope
This manual is intended for use by experienced technicians familiar with similar types of communication
equipment. It contains all service information required for the equipment and is current as of the
publication date. Content that do not be marked is the compatible part that old version and new version
can use together. The incompatible part has the hint.
Old Version
TM-600
VHF Includes machines with material No. of main board is 410M600100730
and Number below (for example, 410M600100720)
UHF Includes machines with material No. of main board is 410M600100860
and below
New Version
TM-600
VHF Includes machines with material No. of main board is 410M600100750
and above (for example, 410M600100760).
UHF Includes machines with material No. of main board is 410M600100870
and above
Precautions
Safety Standards
Do not operate your radio when someone is either touching or standing within 2 or 3 feet of the
antenna, to avoid the possibility of radio frequency burns or related physical injury.
Do not operate the radio near electrical blasting caps or in an explosive atmosphere.
Switch off the radio while refueling or parking at gas station.
Turn off your radio in any place where posted notices instruct you to do so.
Do not modify the radio for any reason.
Do not expose the radio to direct sunlight over a long time, nor place it close to heating source.
Do not place the radio in excessively dusty, humid areas, nor on unstable surfaces.
Refer the service to qualified technicians only.

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Operation Safety Guidelines
For vehicles equipped with electronic anti-skid braking systems, electronic ignition systems or
electronic fuel injection systems, interferences may occur during the radio transmission. If the
foregoing electronic equipments are installed on your vehicle, please contact your dealer for further
assistance to make sure that the radio transmission will not interfere with these equipments.
For radio installation in vehicles fueled by LP gas with LP gas container within interior of the
vehicles, the following precautions are recommended for personal safety.
(1) Any space containing radio equipment shall be isolated by a seal from the space in which the
LP gas container and its fittings are located.
(2) Remote (outside) fitting connections shall be used.
(3) Good ventilation is required for the container space.
Installation Safety Guidelines
Do not mount the mobile radio overhead or on a sidewall unless you take special precautions.
If someone were to remove the radio and fail to replace it properly, road shock could bump the radio
loose, and the falling radio could, in some circumstances, cause serious injury to the driver or a
passenger. In a crash, even when properly installed, the radio could break loose and become a
dangerous projectile.

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Radio Overview
Front Panel
①Volume Knob
②Low Power Indicator
③Scan Indicator
④Channel Display Numeric LED
⑤Channel Up Key
⑥Channel Down Key
⑦RX/TX Indicator
⑧On/Off Key
⑨P2 Key
⑩P1 Key
⑪Mic Jack
Rear Panel Overview
①15PIN (for external expansion)
②External Speaker Jack
Used to connect external speaker and only available for the plug of 3.5 mm (Please refer to Test
Cable for Speaker Output of Tuning Mode for details).
③Power Inlet
Adopt HYT-authorized DC power cable and 13.6 V DC power.

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④Antenna Pedestal
Used to connect external antenna.
Microphone
8-segment LED Display
Figure 1 8-segment LED

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Software Specification
Frame of Radio Modes
Keypad Entry for Mode Startup
Mode Display Operation Remarks
User Mode Channel Number Power on the radio to enter User Mode Conventional Mode
Tuning Mode 0 Press and hold down [P1] to turn the radio on.
Model Set Mode 0 Press and hold down [P2] to turn the radio on.
Clone Mode C Press [P1] and [P2] simultaneously to turn the radio on.
PC Mode No Display Connect PC with mobile radio via programming cable
and send commands via PC.
Key Assignment
Programmable functional keys [P1]/[P2] and [▲ ] / [▼ ].
Key Assignment
No. Key Settings Display Remarks
1 [P1]
Off CH Number None
CH Up CH Number Channel up
CH Down CH Number Channel down
MONI A CH Number
MONI A:
Monitor Unmute-Momentary
MONI B CH Number
MONI B:
Monitor Unmute-Toggle
MONI C [Default] CH Number
MONI C:
Carrier Squelch-Momentary
PC Mode
Tuning Mode
Conventional ModeUser Mode
Model Set Mode
Clone Mode
Wired Clone Mode
Wireless Clone Mode

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MONI D CH Number
MONI D:
Carrier Squelch-Toggle
User Selectable Tone UST Number (0.-9.) CTCSS/CDCSS Signalling
Select 2-tone 2-tone Number (0.-9.) Select 2-Tone encode
TX Power CH Number Switch TX power
Scan ● Scan
Add/Delet ● Temporarily delete nuisance channel
Reverse CH Number Reverse frequency
Talk Around CH Number Talk Around
SEL SQL SQL Number (0.-9.) Select SQL
Home CH HomeCH Number(1-8) Home channel
Public Address P Public address
Scrambler CH Number Scrambler
Compander CH Number Compander
Emergency call EmergencyCH Number (1- 8) Emergency call
HDC Encode Call List Number HDC Call
Lone worker L. or L Lone worker
Whisper R. or R Whisper
AUX A None AUX A
AUX B None AUX B
2 [P2]
Off CH Number None
CH Up CH Number Channel up
CH Down CH Number Channel down
MONI A CH Number
MONI A:
Monitor Unmute-Momentary
MONI B CH Number
MONI B:
Monitor Unmute-Toggle
MONI C CH Number
MONI C:
Carrier Squelch-Momentary
MONI D CH Number
MONI D:
Carrier Squelch-Toggle
User Selectable Tone UST Number (0.-9.) CTCSS/CDCSS signalling
Sel 2-tone 2-tone Number (0.-9.) Select 2-Tone encode
Selectable TX Power CH Number Switch TX Power
Scan [Default] ● Scan
Add/Delet ● Temporarily Delete nuisance channel
Reverse CH Number Reverse
Talk Around CH Number Talk Around
SEL SQL SQL Number (0.-9.) Select SQL
Home CH HomeCH Number (1- 8) Home channel
Public Address P Public Address
Scrambler CH Number Scrambler
Compander CH Number Compander

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Emergency call EmergencyCH Number(1- 8) Emergency call
HDC Encode Call List Number HDC Call
Lone worker L. or L Lone worker
Whisper R. or R Whisper
AUX A None AUX A
AUX B None AUX B
3 [▲ ] ( [UP] )
Off CH Number None
CH Up [Default] CH Number Channel up
CH Down CH Number Channel down
MONI A CH Number
MONI A:
Monitor Unmute-Momentary
MONI B CH Number
MONI B:
Monitor Unmute-Toggle
MONI C CH Number
MONI C:
Carrier Squelch-Momentary
MONI D CH Number
MONI D:
Carrier Squelch-Toggle
User Selectable Tone UST Number(0.-9.) CTCSS/CDCSS signalling
Sel 2-tone 2-tone Number(0.-9.) Select 2-Tone encode
TX Power CH Number Switch TX Power
Scan ● Scan
Add/Delet ● Temporarily Delete nuisance channel
Reverse CH Number Reverse
Talk Around CH Number Talk Around
SEL SQL SQL Number(0.-9.) Select SQL
Home CH HomeCH Number (1-8) Home channel
Public Address P Public Address
Scrambler CH Number Scrambler
Compander CH Number Compander
Emergency call EmergencyCH Number(1- 8) Emergency call
HDC Encode Call List Number HDC Call
Lone worker L. or L Lone worker
Whisper R. or R Whisper
AUX A None AUX A
AUX B None AUX B
4[▼ ]([DOWN])
Off CH Number None
CH Up CH Number Channel up
CH Down [Default] CH Number Channel down
MONI A CH Number
MONI A:
Monitor Unmute-Momentary
MONI B CH Number
MONI B:
Monitor Unmute-Toggle

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MONI C CH Number
MONI C:
Carrier Squelch-Momentary
MONI D CH Number
MONI D:
Carrier Squelch-Toggle
User Selectable
Tone UST Number(0.-9.) CTCSS/CDCSS signalling
Sel 2-tone 2-tone Number(0.-9.) Select 2-Tone encode
TX Power CH Number Switch TX Power
Scan ● Scan
Add/Delet ● Temporarily Delete nuisance channel
Reverse CH Number Reverse
Talk Around CH Number Talk Around
SEL SQL SQL Number(0.-9.) Select SQL
Home CH HomeCH Number(1-8) Home channel
Public Address P Public Address
Scrambler CH Number Scrambler
Compander CH Number Compander
Emergency call EmergencyCH Number(1- 8) Emergency call
HDC Encode Call List Number HDC Call
Lone worker L. or L Lone worker
Whisper R. or R Whisper
AUX A None AUX A
AUX B None AUX B
5 Hook/Moni
Hook test CH Number Selected when using palm microphone.
Moni CH Number Selected when using desktop
microphone.
6 Selector Knob Volume knob CH Number Volume knob
Note: the above “CH Number”indicates any number between 1 and 8.
PC Mode
Connect the mobile radio with PC via programming cable. The data can be written to the radio from PC,
and then saved into the EEPROM. Data programming and radio tuning are accessible by programming
software.
(1) LED glows green when data is written to the radio and red when data is read from the radio. Radio
will restart automatically when programming is completed.
(2) The following parameters can be set through the programming software.
HighTX Power
Low TX Power
Maximum Frequency Deviation
CDCSS Balance
CTCSS Deviation（67.0Hz）
CTCSS Deviation（151.4Hz）
CTCSS Deviation（254.1Hz）
CDCSS Deviation
DTMF Deviation

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MSK Deviation
Single Tone Deviation
RX sensitivity
Squelch On Level 9
Squelch On Level 3
Squelch Off Level 9
Squelch Off Level 3
Clone Mode
Data can be transferred from radio to radio either by wired cloning or wireless cloning.
Wired Clone Mode
1) Press and hold down [P1] and [P2] simultaneously to power on the source radio. The radio enters
wired clone mode with “C”displayed on numeric display and LED flashes orange twice, or the radio
enters User Mode when Clone Mode is set by your local dealer.
2) Press [▲ ] to toggle between Dealer Clone and Factory Clone Mode. “C”or “C.”appears on the
display when the corresponding mode is selected.
3) Unlike Factory Clone Mode, tuning settings and embedded messages are not covered in Dealer
Clone Mode. Factory Clone Mode clones all data. Dealer Clone Mode is the default mode.
4) Connect the target radio with the source radio via programming cable and turn the target radio on.
5) Press [P2] to start cloning. The LED of source radio glows red and data is cloned to the target
radio.Target radio glows green when it is cloning. When all data is successfully received, the LED of
source radio goes down and the target radio automatically enters User Mode; otherwise, its LED
flashes red.
6) Press [P2] to return the source radio to Clone Mode and “C”or “C.”appears on the display. Repeat
the above steps to continue wired clone.
Wireless Clone Mode
1) Press and hold down [P1] and [P2] simultaneously to power on the source radio. The radio enters
Wired Clone mode with “C”displayed on the display and LED flashes orange twice, or the radio
enters User Mode when Clone Mode is set by your dealer.
2) Press [P1] to enter Wireless Clone Mode and “1”appears on numeric display. Press [P1] again to
exit and return to Wired Clone Mode.
3) Press [▲ ] to toggle between Dealer Clone and Factory Clone Mode. “1”or”1.”appears on the
display when the corresponding mode is selected. “1”indicates Dealer Mode while “1.”Indicates
Factory Mode. Press [▼ ] to select the channel for cloning and its channel number displayed on the
numeric LED. The dot beside right corner of “1”going out indicates that the current condition is
dealer clone; otherwise, it is factory clone mode.
Unlike Factory Clone Mode, tuning settings and embedded messages are not covered in Dealer
Clone Mode. Factory Clone Mode clones all data.
Dealer Clone Mode is the default mode.
4) Repeat step1-2 to operate the target radio, the frequency is set the same as that of source radio.
Press [P2] on the source radio to start cloning.
5) The LED of source radio glows red while that of target radio glows orange during cloning.
6) When data transmission is completed, the LED of source radio goes out. Repeat the steps above to
continue cloning. When all data is successfully received, the target radio automatically enters User
Mode; otherwise, its LED flashes red.

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Note: Clone Mode can be enabled/disabled by your local dealer. Wired clone is accessible only when
Clone Mode is enabled.
Tuning Mode
The operations of Tuning Mode are described as following:
1) Press [P1] to power on the radio. The radio enters Tuning Mode and its LED flashes red twice.
2) Use [▲ ] / [▼ ] to select setting items among 0-9, A-F and(0.-9., A.-F.)appears on the display.
3) Sub-item and corresponding display:
i. As for setting items 0-9 and A-B: Press [P2] to enter the item. Press [▲ ] / [▼ ] to tune the
parameter. Press [P2] again to save data and move to next item; or press [P1] to return to
previous menu without saving data.
ii. As for setting item C-F: Press [P2] to enter the item (operation of numeric LED display is the
same as i) and (0-4) appears on the display. Press [P2] again to automatically modify the
parameter. The display changes to (0-4). Press [P2] to save data and move to next item; or press
[P1] to return to previous menu without saving data.
Note: 0.: Center frequency; 1.: Low frequency; 2.: High frequency; 3.: Center frequency of medium band;
4.: Center frequency of narrow band; 5.: Low frequency of narrow band; 6.: High frequency of narrow
band; 7: Low-medium frequency; 8: Medium-high frequency.
Setting items and display
Setting item Main LCD Wideband/
Narrowband Frequency Sub LCD Description
Tx High Power 0 High frequency
Wideband
Center 0．No signalling
Low 1．No signalling
High 2．No signalling
Tx Low Power 1 Low frequency
Wideband
Center 0．No signalling, Low power
indicator on.
Low 1．No signalling, Low power
indicator lights.
High 2．No signalling, Low power
indicator lights.
Max Deviation 2
Wideband
Center 0．No signalling
Low 1．No signalling
High 2．No signalling
Medium Center 3．No signalling
Narrowband
Center 4．No signalling
Low 5．No signalling
High 6．No signalling
CDCSS
Balance 3
Wideband
Center 0．100Hz square wave
Low 1．100Hz square wave
High 2．100Hz square wave
Medium Center 3．100Hz square wave
Narrowband Center 4．100Hz square wave
CTCSS
Deviation 4 Wideband Center 0．CTCSS: 67.0Hz Low 1．CTCSS: 67.0Hz

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Medium Center 3．CTCSS: 67.0Hz
Narrowband Center 4．CTCSS: 67.0Hz
5
Wideband
Center 0．CTCSS: 151.4Hz
Low 1．CTCSS: 151.4Hz
High 2．CTCSS: 151.4Hz
Medium Center 3．CTCSS: 151.4Hz
Narrowband Center 4．CTCSS: 151.4Hz
6
Wideband
Center 0．CTCSS: 254.1Hz
Low 1．CTCSS: 254.1Hz
High 2．CTCSS: 254.1Hz
Medium Center 3．CTCSS: 254.1Hz
Narrowband Center 4．CTCSS: 254.1Hz
CDCSS
Deviation 7
Wideband
Center 0．CDCSS: 023N
Low 1．CDCSS: 023N
High 2．CDCSS: 023N
Medium Center 3．CDCSS: 023N
Narrowband Center 4．CDCSS: 023N
DTMF Deviation 8
Wideband
Center 0．DTMF: 9
Low 1．DTMF: 9
High 2．DTMF: 9
Medium Center 3．DTMF: 9
Narrowband Center 4．DTMF: 9
MSK Deviation 9
Wideband
Center 0．0XAAA…
Low 1．0XAAA…
High 2．0XAAA…
Medium Center 3．0XAAA…
Narrowband Center 4．0XAAA…
Single Tone
Deviation A
Wideband
Center 0．1KHz
Low 1．1KHz
High 2．1KHz
Medium Center 3．1KHz
Narrowband Center 4．1KHz
RX Sensitivity
B
- Low 1．No signalling,SQ off
-Low-medium
frequency 7．No signalling,SQ off
- Center 0．No signalling,SQ off
- Medium-high 8．No signalling,SQ off
- High 2．No signalling,SQ off
SQL On C
SQL 9
Wideband
Center 0．No signalling
Low 1．No signalling
High 2．No signalling
SQL 9 Medium Center 3．No signalling
SQL 9 Narrowband Center 4．No signalling
Low 5．No signalling

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High 6．No signalling
D
SQL 9 Wideband
Center 0．No signalling
Low 1．No signalling
High 2．No signalling
SQL 9 Medium Center 3．No signalling
SQL 9 Narrowband
Center 4．No signalling
Low 5．No signalling
High 6．No signalling
SQL Close
E
SQL 9 Wideband
Center 0．No signalling
Low 1．No signalling
High 2．No signalling
SQL 9 Medium Center 3．No signalling
SQL 9
Narrowband
Center 4．No signalling
Low 5．No signalling
High 6．No signalling
F
SQL 3 Wideband
Center 0．No signalling
Low 1．No signalling
High 2．No signalling
SQL 3 Medium Center 3．No signalling
SQL 3 Narrowband
Center 4．No signalling
Low 5．No signalling
High 6．No signalling
Model Set Mode
1. Press [P2] to turn the radio on. The radio enters Model Set Mode after the LED flashes green twice.
The selected model number is displayed by numeric LED.
2. Press [▲ ] / [▼ ] to choose model No. 0-5
3. Press [P2] to confirm. LED glows orange and the radio resets; then the radio enters User Mode after
reset.
Notes:
1. Once [P2] key is pressed to set the new model, the previously stored channel data (frequency,
CTCSS/CDCSS, channel function settings) will be cleared, and part of functions also changes.
Therefore, do not make this operation unless it’s very necessary.
2. Initialization Data Table and frequency range (FL: lowest frequency- FH: highest frequency -FC:
center frequency) of different models are shown in the following table.
Model RX/TX 1 ( C ) 2 ( L ) 3 ( H ) 4 5 6 7 8
0 RX(MHz) 155.15 136.15 173.85 145.55 164.50 155.00 155.20 155.40
(V) TX(MHz) 155.00 136.00 174.00 145.50 164.50 155.00 155.20 155.40
1 RX(MHz) 435.15 400.15 469.85 417.55 452.50 435.00 435.20 435.40
(U1) TX(MHz) 435.00 400.00 470.00 417.50 452.50 435.00 435.20 435.40
2 RX(MHz) 475.15 450.15 499.85 462.55 487.50 475.00 475.20 475.40
(U2) TX(MHz) 475.00 450.00 500.00 462.50 487.50 475.00 475.20 475.40
3 RX(MHz) 495.15 470.15 519.85 482.55 507.50 495.00 495.20 495.40
(U3) TX(MHz) 495.00 470.00 520.00 482.50 507.50 495.00 495.20 495.40

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4 RX(MHz) 375.15 350.15 399.85 362.55 387.50 375.00 375.20 375.40
(U4) TX(MHz) 375.00 350.00 400.00 362.50 387.50 375.00 375.20 375.40
5 RX(MHz) 455.15 440.15 469.85 447.55 462.50 455.00 455.20 455.40
(U5) TX(MHz) 455.00 440.00 470.00 447.50 462.50 455.00 455.20 455.40
TM-600 VHF:136-174MHz
TM-600 U1:400-470MHz
TM-600 U2:450-500MHz
TM-600 U3:470-520MHz
TM-600 U4:350-400MHz
TM-600 U5:440-470MHz
CH 1 2 3 4 5 6 7 8
CTCSS RX OFF OFF OFF OFF CTS67.0HZ DI454 151.4 DI454
CDCSS TX OFF OFF OFF OFF CTS67.0HZ DI454 151.4 DI454
PWR TX H H H L L L L L
CH
NAME
CH 1
Wide
CH 2
Wide
CH 3
Wide
CH 4
N
CH 5
Wide
CH 6
Wide
CH 7
N
CH 8
N

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Circuit Description
Frequency Configuration
The receiver utilizes double conversion superheterodyne. The first IF is 49.95MHz and the second is
450KHz. The first local oscillator signal is supplied by PLL circuit. The second (50.4MHz) is generated
from the frequency tripling of TCXO (16.8MHz). The PLL circuit generates the frequencies required for
transmission. (See Fig.1).
Frequency Range VHF:136MHz— 174MHz
UHF:400MHz— 470MHz；
450MHz— 500MHz；
470MHz— 520MHz；
350MHz— 400MHz；
440MHz— 470MHz；
Receiver Circuit
The receiver section configuration is shown as Fig. 1.
Fig 1 Receiver Circuit
1. High Frequency Bandpass Amplifier Circuit
It consists of BPF (LC resonant circuit where D107, D108 and D109 are located) and RF amplifier (Q111)
and the final-stage BPF(D110 and D111). The range of bandpass frequency is the frequency range of the
radio itself. The signal is filtered by the BPF to eliminate unwanted signals before going to the first mixer.
2. The First Mixer
The signal from BPF is mixed with the first local oscillator signal from PLL circuit at the first mixer (Q112)

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to become a 49.95MHz first IF signal. The first IF signal is then fed through crystal filter (IF200) to further
remove spurious signals.
3. IF Amplifier
The first IF signal is amplified by Q113 and then enters IC102 (TA31136FN), where the signal is mixed
again with the second local oscillator signal (50.4MHz) to become a 450KHz second IF signal. The
second IF signal is then fed through a ceramic filter (N: CF202; W: CF203) to eliminate unwanted signal.
The resulting signal then is detected by IC102 and output from Pin 9 as an Audio signal.
4. Audio Amplifier
The audio signal obtained from IC102 is amplified and filtered by IC402 before being amplified by IC401
(the received signalling inputted into CPU for decode). The processed signalling passes through Q406
(AF MUTE) and is amplified by IC405. The amplified signal is fed to K301 (volume control), Q511 (SP
MUTE) before entering Audio AMP (IC511). The outputted Audio signal drives the Speaker.
5. Squelch
The output Audio signal from IC102 passes through IC102 Pin8 and is amplified by IC102 again, then is
filtered and rectified to produce an SQL level. The SQL level is compared with the existing reference
level in CPU (IC502) to generate a level to control AF MUTE and SP MUTE, which determines whether
to output sounds from speaker by controlling Q406 and Q511.
Transmitter Circuit
The transmitter circuit is composed of MIC circuit, modulation circuit, RF driver, final-stage power
amplification circuit and APC circuit.
Fig 2 Transmitter Circuit
1. MIC and modulation circuit
The audio signal from MIC is amplified by IC405 before being pre-emphasized and encoded by IC401.
The output audio is added into signalling and then is fed through VCO for modulation.

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2. RF Driver and Final-stage Power Amplification Circuit
The TX-RF signal outputted from Q703 in VCO circuit is amplified by Q101, driver Q110 and Q109, The
amplified signal is then fed to IC101 (final-stage amplifier) and passes through LPF before reaching the
antenna terminal.
3. APC
The APC circuit stabilizes the output power at a predetermined level. D101 and D102 transform the
signal from detector to DC voltage, which is then compared with the reference voltage from CPU in
IC104 and outputted as DC control voltage. The DC control voltage controls the output power by
controlling the grid of IC101.
PLL Circuit
The frequency of the transmit signal and the receiver first local oscillator signal are generated by PLL
circuit. PLL circuit consists of TX frequency oscillator (Q701), RX frequency oscillator (Q702), buffer
amplifier (Q703), RF amplifier (Q102), PLL IC (IC801), LPF and TX/RX VCO control switch (Q704,
Q706).
In transmit mode, IC120 transmits the frequency data to PLL IC and drives PLL IC. Q704 is turned on to
activate TX VCO. The outputted signal is amplified by Q703, Q102, and then divided by PLL IC into
2.5KHz, 5KHz or 6.25KHz signal. The divided signal is compared with 2.5KHz, 5KHz or 6.25KHz
reference signal from 16.8MHz crystal oscillator (2.5 PPM frequency stability) in the phase comparator.
The frequency control voltage outputted from the phase comparator is sent to TX VCO after passing
through LPF (Q802, Q803). In the meantime, modulation signal (TX) is passed to TX VCO for frequency
modulation.
The working principle in receive mode is similar to that in transmit mode.
Fig 3 PLL Circuit
Control Circuit
The control circuit is composed of CPU, reset IC and power supply control circuit.
1. CPU
IC502 (CPU) operates at 9.8304MHz. CPU controls the data transmission among E2PROM (IC501), RX
circuit, TX circuit, control circuit, display circuit and peripheral circuit.

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Fig 4 Control Circuit
2. Power Supply
Power supply of the radio is derived from the battery which supplies battery B+. D135 and D137 are
over-voltage protection diodes. Power-on/off can be controlled by software.
Fig 5 Power Supply Circuit
Vout provides power supply for IC601, IC602 and IC803, which produces 8V, 5V, 3.3V voltage to the
circuit.

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Display Circuit
Display circuit is comprised of CPU (IC502), LCD module, 8-segment numeric LED, LED and other
components. Radio features are programmable by P1-P4. Data is displayed on the 8-segment LED in
alphanumeric form.
Fig 6. Display Circuit