Related Manuals for Motorola LB3 (42.0 - 50.0MHz)
Summary of Contents for Motorola LB3 (42.0 - 50.0MHz)
- Page 1 Professional Radio GM Series LB1 (29.6 - 36.0MHz) LB2 (36.0 - 42.0MHz) LB3 (42.0 - 50.0MHz) Service Information Issue: August 2002...
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Page 2: Computer Software Copyrights
Accordingly, any copyrighted Motorola computer programs contained in the Motorola products described in this manual may not be copied or reproduced in any manner without the express written permission of Motorola. Furthermore, the purchase of Motorola... -
Page 3: Table Of Contents
Table of Contents Chapter 1 MODEL CHART AND TECHNICAL SPECIFICATIONS 1.0 GM360 Model Chart.....................1-1 2.0 Technical Specifications ..................1-1 Chapter 2 THEORY OF OPERATION 1.0 Introduction ......................2-1 2.0 Low Band Receiver.....................2-2 2.1 Receiver Front-End ..................2-2 2.2 Front-End Band-Pass Filters & Pre-Amplifier ..........2-3 2.3 First Mixer ......................2-3 2.4 High Intermediate Frequency (IF) and Receiver Back End ......2-3 2.5 Low Intermediate Frequency (IF) and Receiver Back End......2-4... - Page 4 Chapter 4 Low Band PCB/SCHEMATICS/PARTS LISTS 1.0 Allocation of Schematics and Circuit Boards ............4-1 1.1 Controller Circuits ....................4-1 2.0 LB1 25-60W PCB 8486206B06 / Schematics ............. 4-5 2.1 LB1 25-60W PCB 8486206B06 Parts List ............4-15 3.0 LB2 25-60W PCB 8486207B05 / Schematics ........... 4-18 3.1 LB2 25-60W PCB 8486207B05 Parts List ............
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Page 5: Model Chart And Technical Specifications
Chapter 1 MODEL CHART AND TECHNICAL SPECIFICATIONS GM360 Model Chart GM Series Low Band 29-50 MHz Model Description MDM25BKF9AN5_E GM360 LB1, 29.0-36.0 MHz, 25-60W, 255 Ch MDM25CKF9AN5_E GM360 LB2, 36.0-42.0 MHz, 25-60W, 255 Ch MDM25DKF9AN5_E GM360 LB3, 42.0-50.0 MHz, 25-60W, 255 Ch Item Description GCN6114_... - Page 6 MODEL CHART AND TECHNICAL SPECIFICATIONS Transmitter *Frequencies - Full Bandsplit LB1 29.7-36.0 MHz LB2 36.0-42.0 MHz LB2 42.0-50.0 MHz Channel Spacing 12.5/20/25 kHz 12.5/20/25 kHz 12.5/20/25 kHz Frequency Stability ±5.0 ppm ±5.0 ppm ±5.0 ppm (-30°C to +60°C, +25° Ref.) Power 25-60W 25-60W...
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Page 7: Theory Of Operation
Chapter 2 THEORY OF OPERATION Introduction This Chapter provides a detailed theory of operation for the LowBand circuits in the radio. For details of the theory of operation and trouble shooting for the the associated Controller circuits refer to the Controller Section of this manual. -
Page 8: Low Band Receiver
THEORY OF OPERATION Low Band Receiver Receiver Front-End The low band receiver is bandsplit into three ranges depending on radio model, covering frequencies from 29.7 to 36.0 MHz, 36.0 to 42.0 MHz, or 42.0 to 50.0 MHz. The circuitry of the three models is identical except for component value differences. -
Page 9: Front-End Band-Pass Filters & Pre-Amplifier
Low Band Receiver There are two 2-pole 10.7 MHz crystal filters in the high-IF section and two switched pairs of 455 kHz ceramic filters in the low-IF section to provide the required adjacent channel selectivity. The second IF at 455 kHz is mixed, amplified and demodulated in the IF IC. The processing of the demodulated audio signal is performed by an audio processing IC located in the controller section. -
Page 10: Low Intermediate Frequency (If) And Receiver Back End
THEORY OF OPERATION presented to the high-Q crystal filters FL1102 and FL1103, would cause ringing of the filter response, stretching an otherwise narrow impulse into a long and audible output waveform. Therefore, source follower stage Q1104 isolates the blanker switches from the crystal filters, providing a consistent source impedance via matching network L1106, L1107 and associated components. -
Page 11: Low Band Transmitter Power Amplifier (Pa) 25-60 W
Low Band Transmitter Power Amplifier (PA) 25-60 W Low Band Transmitter Power Amplifier (PA) 25-60 W The radio’s 60 W PA is a three-stage amplifier used to amplify the output from the VCO to the radio transmit level. The line-up consists of three stages which utilize LDMOS technology. The first stage is pre-driver (U1401) that is controlled by pin 4 of PCIC (U1503) via Q1504 and Q1505 (CNTLVLTG). -
Page 12: Final Stage
THEORY OF OPERATION antenna of the radio. The variation in the driver’s output power is limited by controlling its DC current. The driver’s DC current is monitored by measuring the voltage drop across current-sense resistors R1473-6, and this voltage is compared to a reference voltage on pin 6 of U1402-2. If the current through the sense resistors decreases, the circuit increases the bias voltage on the gate of Q1401 via Q1404. -
Page 13: Tx Safety Switch
Low Band Frequency Synthesis current until equilibrium of the two compared voltages is reached. The current through Q1503 develops a voltage across R1513 which is exactly proportional to the DC current of the final stages. This voltage is applied to the RF IN port of the PCIC (pin 1). The PCIC has internal digital to analog converters (DACs) which provide a reference voltage of the control loop. - Page 14 THEORY OF OPERATION for low frequency digital modulation, a balance attenuator to balance the high frequency analog modulation and low frequency digital modulation, a 13V positive voltage multiplier, a serial interface for control, and finally a super filter for the regulated 9.3 volt supply. Regulated 9.3 volts DC applied to the super filter input (U1201 pin 30) delivers a very low noise output voltage of 8.3 volts DC (VSF) at pin 28.
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Page 15: Voltage Controlled Oscillator (Vco)
Low Band Frequency Synthesis Voltage Controlled Oscillator (VCO) Separate VCO and buffer circuits are used for receiver injection and transmitter carrier frequency generation. Since the receiver uses high-side injection, the receiver VCO frequency range is 10.7 MHz above the transmit VCO range. The VCO/buffers are bandsplit into three ranges depending on radio model, covering radio operating frequencies of 29.7 to 36.0 MHz, 36.0 to 42.0 MHz, or 42.0 to 50.0 MHz. -
Page 16: Synthesizer Operation
2-10 THEORY OF OPERATION The VCO output is taken from the source and applied to the first buffer transistor (Q1304 receive, Q1307 transmit). The first buffer output is further amplified by the second buffer transistor (Q1305 Rx, Q1308 Tx) before being applied to the receiver first mixer or transmitter first stage input. In TX mode the modulation signal coming from the LVFRAC-N synthesizer IC (MODOUT, U1201 pin 41) is superimposed on the DC steering line voltage by capacitive divider C1215, C1208 and C1212, causing modulation of the TX VCO using the same varactor as used for frequency control. -
Page 17: Troubleshooting Flow Chart For Transmitter
Chapter 3 LOW BAND TROUBLESHOOTING CHARTS Troubleshooting Flow Chart for Transmitter START No or Low Power Out Check Pressure Pad and/or Safety Switch Circuitry Switch Voltage > 1A < 1A @Drains of CURRENT Q1402 & Q1403 Look for <<18V pp short on RF @ Supply Line... -
Page 18: Troubleshooting Flow Chart For Receiver (Sheet 1 Of 2)
Low Band TROUBLESHOOTING CHARTS Troubleshooting Flow Chart for Receiver (Sheet 1 of 2) START Bad SINAD Bad 20dB Quieting No Recovered Audio Audio Check Controller (in the case of no audio). at pin 8 of U1103 Or else go to “B” Spray or inject 10.7MHz into XTAL Filter FL1102. -
Page 19: Troubleshooting Flow Chart For Receiver (Sheet 2 Of 2)
Troubleshooting Flow Chart for Receiver Troubleshooting Flow Chart for Receiver (Sheet 2 of 2) Inject RF into J1401 Trace IF signal Signal at signal at from C1036 to pin 2 of Q1106 Q1106. Check for U1051 collector bad XTAL filter. Before replacing U1103, check U1103 voltages. -
Page 20: Troubleshooting Flow Chart For Synthesizer
Low Band TROUBLESHOOTING CHARTS Troubleshooting Flow Chart for Synthesizer 5V at Check 5V U1201 pins 5, Regulator U1250, Start 13, 20, 24 & L1201 & R1201 36 ? Visual Check D3201, Correct check of the C3203, C3205, & Problem Board OK C3206 16.8MHz 16.8MHz... -
Page 21: Troubleshooting Flow Chart For Vco
Troubleshooting Flow Chart for VCO Troubleshooting Flow Chart for VCO RX - VCO TX - VCO Low or NO RF Signal Low or no RF Signal at Input to PA at U1051 Visual Check Visual Check Correct of Board of Board Problem Make sure Synthesizer is 8.5V DC... - Page 22 Low Band TROUBLESHOOTING CHARTS...
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Page 23: Allocation Of Schematics And Circuit Boards
Chapter 4 LOW BAND PCB/SCHEMATICS/PARTS LISTS Allocation of Schematics and Circuit Boards Controller Circuits The Low Band circuits are contained on the printed circuit board (PCB) which also contains the Controller circuits. This Chapter shows the schematics for the Low Band circuits only, refer to the Controller section for details of the related Controller circuits . - Page 24 Low band pcb/schematics/parts lists Table 4-3 LB3 25-60W Diagrams and Parts Lists PCB : 8485908z03 Main Board Top Side Page 4-31 8485908z03 Main Board Bottom Side Page 4-32 SCHEMATICS Power Amplifier 25-60W (Sheet 1 of 2) Page 4-33 Power Amplifier 25-60W (Sheet 2 of 2) Page 4-34 Voltage Controlled Oscillator Page 4-35...
- Page 25 Allocation of Schematics and Circuit Boards Table 4-5 LB2 25-60W Diagrams and Parts Lists PCB : 8486207B07 Main Board Top Side Page 4-51 8486207B07 Main Board Bottom Side Page 4-52 SCHEMATICS Power Amplifier 25-60W (Sheet 1 of 2) Page 4-20 Power Amplifier 25-60W (Sheet 2 of 2) Page 4-21 Voltage Controlled Oscillator...
- Page 26 Low band pcb/schematics/parts lists...