Page 2 of 93
CONTENTS
1. INTRODUCTION ..........................................................................................................................5
1.1. M
ODEL
N
UMBERS
....................................................................................................................5
2. ITEMS SUPPLIED........................................................................................................................5
2.1. ACCESSORIES.....................................................................................................................6
3. OPERATING THE RADIO............................................................................................................7
4. THEORY OF OPERATION...........................................................................................................7
4.1. THE
MICROPROCESSOR....................................................................................................7
4.1.1. Microprocessor I/O Signals.............................................................................................8
4.1.2. Switch Operation ............................................................................................................8
4.1.3. Backlights.......................................................................................................................9
4.1.4. Microprocessor Clock and Beat Shift Function................................................................9
4.1.5. Microprocessor Reset.....................................................................................................9
4.1.6. Discrete Control Signals ...............................................................................................10
4.2. AUDIO
AND
TONE
SIGNALLING
CIRCUITS.......................................................................11
4.2.1. Received Voice Audio Processing................................................................................11
4.2.2. Received Tone Processing...........................................................................................12
4.2.3. Transmit Audio Processing...........................................................................................12
4.2.4. Transmit Tone Processing............................................................................................13
4.3. SYNTHESIZER
SECTION...................................................................................................14
4.3.1. Reference Oscillator.....................................................................................................14
4.3.2. Voltage Doubler............................................................................................................15
4.3.3. Loop Filter.....................................................................................................................15
4.3.4. Transmit VCO...............................................................................................................15
4.3.5. Receive VCO................................................................................................................15
4.3.6. VCO Power Switching and Buffering.............................................................................16
4.4. RECEIVER
SECTION..........................................................................................................17
4.4.1. Antenna Transmit/Receive switching circuit..................................................................17
4.4.2. First RF Filter................................................................................................................17
4.4.3. RF Amplifier..................................................................................................................17
4.4.4. Second RF Filter...........................................................................................................18
4.4.5. Mixer Circuit..................................................................................................................18
4.4.6. First IF Filter .................................................................................................................18
4.4.7. First IF Amplifier Circuit.................................................................................................18
4.4.8. Second LO Tripler Circuit..............................................................................................18
4.4.9. Second IF Circuit (FM IF IC).........................................................................................19
4.4.10. Noise Squelch Detector.............................................................................................19
4.5. TRANSMITTER
SECTION...................................................................................................21
4.5.1. Low Power Transmit Amplifier ......................................................................................21
4.5.2. Transmit Driver Amplifier ..............................................................................................21
4.5.3. Final Power Amplifier....................................................................................................21
4.5.4. PA Switching Circuit. ....................................................................................................22
4.6. POWER
SUPPLY................................................................................................................23
4.6.1. Battery connections and Protection circuit ....................................................................23
4.6.2. Main Regulator .............................................................................................................23
4.6.3. Transmit and Receive Power control circuit..................................................................23
4.7. MISCELLANEOUS
FUNCTIONS.........................................................................................23
4.7.1. Switches.......................................................................................................................23
4.7.2. Indicators......................................................................................................................23
4.7.3. Volume Control.............................................................................................................23
4.7.4. Battery Monitoring.........................................................................................................24
5. DISASSEMBLY..........................................................................................................................25
5.1. A
TTACHING AND
R
EMOVING THE
B
ATTERY
P
ACK
.....................................................................25
