Motorola Gm Series Low Band Info Manual
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Professional Radio GM Series LB1 (29.6 - 36.0MHz) LB2 (36.0 - 42.0MHz) LB3 (42.0 - 50.0MHz) Service Information Issue: August 2002
ii Computer Software Copyrights The Motorola products described in this manual may include copyrighted Motorola computer programs stored in semiconductor memories or other media. Laws in the United States and other countries preserve for Motorola certain exclusive rights for copyrighted computer programs, including the exclusive right to copy or reproduce in any form, the copyrighted computer program. 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 products shall not be deemed to grant, either directly or by implication, estoppel or otherwise, any license under the copyrights, patents or patent applications of Motorola, except for the normal non-exclusive royalty- free license to use that arises by operation of law in the sale of a product.
iii 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 2.6 Extender (Noise Blanker) ............................................................................. 2-4 3.0 Low Band Transmitter Power Amplifier (PA) 25-60 W ........................................ 2-5 3.1 Power Controlled Stage .................................................................................. 2-5 3.2 Driver Stage .................................................................................................... 2-5 3.3 Final Stage...................................................................................................... 2-6 3.4 Antenna Switch............................................................................................... 2-6 3.5 Harmonic Filter ............................................................................................... 2-6 3.6 Power Control ................................................................................................. 2-6 3.7 TX Safety Switch ............................................................................................ 2-6 4.0 Low Band Frequency Synthesis ......................................................................... 2-7 4.1 Fractional-N Synthesizer ................................................................................ 2-7 4.2 Voltage Controlled Oscillator (VCO) ............................................................... 2-9 4.3 Synthesizer Operation .................................................................................. 2-10 Chapter 3 TROUBLESHOOTING CHARTS 1.0 Troubleshooting Flow Chart for Transmitter ....................................................... 3-1 2.0 Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)...................................... 3-2 2.1 Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)...................................... 3-3 3.0 Troubleshooting Flow Chart for Synthesizer ........................................................ 3-4 4.0 Troubleshooting Flow Chart for VCO ................................................................. 3-5
iv 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 ......................................................... 4-28 4.0 LB3 25-60W PCB 8485908z03 / Schematics .................................................... 4-31 4.1 LB3 25-60W PCB 8485908z03 Parts List.......................................................... 4-41 5.0 LB1 25-60W PCB 8486206B08 / Schematics ................................................... 4-44 5.1 LB1 25-60W PCB 8486206B08 Parts List ......................................................... 4-48 6.0 LB2 25-60W PCB 8486207B07 / Schematics ................................................... 4-51 6.1 LB2 25-60W PCB 8486207B07 Parts List ......................................................... 4-53 7.0 LB3 25-60W PCB 8485908z04 / Schematics .................................................... 4-56 7.1 LB3 25-60W PCB 8485908z04 Parts List.......................................................... 4-58
Chapter 1 MODEL CHART AND TECHNICAL SPECIFICATIONS 1.0 GM360 Model Chart 2.0 Technical Specifications Data is specified for +25°C unless otherwise stated. GM Series Low Band 29-50 MHz Model Description MDM25BKF9AN5_EGM360 LB1, 29.0-36.0 MHz, 25-60W, 255 Ch MDM25CKF9AN5_E GM360 LB2, 36.0-42.0 MHz, 25-60W, 255 Ch MDM25DKF9AN5_EGM360 LB3, 42.0-50.0 MHz, 25-60W, 255 Ch Item Description XXXGCN6114_ Control Head, GM360 XIMUB6003_SField Replaceable Unit (Main Board) GM360 X IMUB6004_S Field Replaceable Unit (Main Board) GM360 XIMUB6005_SField Replaceable Unit (Main Board) GM360 XXXENBN4056_ Packaging, Waris Mobile XXXHKN9402_12V Power Cable XXXMDRMN4025_ Enhanced Compact Microphone XXXRLN4774_3 Point Mount XXX6864110B81_ User Guide, GM360 X = Indicates one of each is required General Specifications Channel Capacity GM360 255 Power Supply 13.2Vdc (10.8 - 15.6Vdc) Dimensions: H x W x D (mm) Height excluding knobsGM360 59mm x 179mm x 250mm (add 9mm for Volume Knob) Weight 2064gr Sealing:Withstands rain testing per MIL STD 810 C/D /E and IP54 Shock and Vibration:Protection provided via impact resistant housing exceeding MIL STD 810-C/D /E and TIA/EIA 603 Dust and Humidity:Protection provided via environment resistant housing exceeding MIL STD 810 C/D /E and TIA/EIA 603
1-2 MODEL CHART AND TECHNICAL SPECIFICATIONS *Availability subject to the laws and regulations of individual countries. Transmitter LB1 LB2 LB3 *Frequencies - Full BandsplitLB1 29.7-36.0 MHzLB2 36.0-42.0 MHzLB2 42.0-50.0 MHz Channel Spacing12.5/20/25 kHz12.5/20/25 kHz12.5/20/25 kHz Frequency Stability (-30°C to +60°C, +25° Ref.)±5.0 ppm±5.0 ppm±5.0 ppm Power 25-60W 25-60W 25-60W Modulation Limiting±2.5 @ 12.5 kHz ±4.0 @ 20 kHz ±5.0 @ 25 kHz±2.5 @ 12.5 kHz ±4.0 @ 20 kHz ±5.0 @ 25 kHz±2.5 @ 12.5 kHz ±4.0 @ 20 kHz ±5.0 @ 25 kHz FM Hum & Noise-40 dB @ 12.5kHz -45 dB @ 20/25kHz-40 dB @ 12.5kHz -45 dB @ 20/25kHz-40 dB @ 12.5kHz -45 dB @ 20/25kHz Conducted/Radiated Emission (ETS)-26 dBm-26 dBm-26 dBm Adjacent Channel Power-60 dB @ 12.5 kHz -70 dB @ 25 kHz-60 dB @ 12.5 kHz -70 dB @ 25 kHz-60 dB @ 12.5 kHz -70 dB @ 25 kHz Audio Response (300 - 3000 Hz)+1 to -3 dB+1 to -3 dB+1 to -3 dB Audio Distortion @1000Hz, 60% Rated Maximum Deviation65 dB Adjacent Channel Selectivity (ETS) 65 dB @ 12.5 kHz 75 dB @ 20 kHz 80 dB @ 25 kHz65 dB @ 12.5 kHz 75 dB @ 20 kHz 80 dB @ 25 kHz65 dB @ 12.5 kHz 75 dB @ 20 kHz 80 dB @ 25 kHz Spurious Rejection (ETS)75 dB @ 12.5 kHz 80 dB @ 20/25 kHz75 dB @ 12.5 kHz 80 dB @ 20/25 kHz75 dB @ 12.5 kHz 80 dB @ 20/25 kHz Rated Audio3W Internal 13W External3W Internal 13W External3W Internal 13W External Audio Distortion @ Rated Audio
Chapter 2 THEORY OF OPERATION 1.0 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.
2-2THEORY OF OPERATION 2.0 Low Band Receiver 2.1 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. The receiver consists of five major blocks: front-end bandpass filters and pre-amplifier, first mixer, high-IF and blanker switches, low-IF and receiver back- end, and “Extender” (noise blanker). Two fixed-tuned bandpass filters perform antenna signal pre- selection. A cross over quad diode mixer converts the signal to the high - IF of 10.7 MHz. High-side first injection is used. Figure 2-1 Low Band Receiver Block Diagram Demodulator Delay Filter Mixer Fixed Tuned Filter RF Amp Tuned Filter Pin Diode Antenna Switch RF Jack Antenna First LO RXINJ Recovered Audio RSSI IF Second LO Crystal Filter 455kHz Filter455kHz Filter 455kHz Filter (12.5kHz)455kHz Filter (12.5kHz)SwitchSwitchSwitchSwitch Limiter IF Amp IF Amp Filter Bank Selection from Synthesizer IC BlankerNoise Blanking Pulses GateBuffer Enable 1st Fixed (25/20kHz) BWSELECT (U1201 Pin 48)4-pole(25/20kHz)
Low Band Receiver2-3 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. 2.2 Front-End Band-Pass Filters & Pre-Amplifier The received signal from the radio’s antenna connector is first routed through the harmonic filter and antenna switch, which are part of the RF power amplifier circuitry, before being applied to the receiver 5-pole antenna filter (L1001-L1005 and associated components). This filter configuration provides more rapid attenuation above the passband to provide better rejection of the half-IF spurious response. A dual hot carrier diode (D1001) limits any inband signal to 0 dBm to prevent damage to the RF pre-amplifier The RF pre-amplifier is an SMD device (Q1001) with collector-base feedback to stabilize gain, impedance, and intermodulation. Transistor Q1002 compares the voltage drop across resistor R1005 with a fixed base voltage from divider R1006 and R1007, and adjusts the base current of Q1001 as necessary to maintain its collector current constant at 25 mA. Operating voltage is from the regulated 9.3V supply (9V3). During transmit, 9.1 volts (9T1) turns on both transistors in U1001, turning off Q1003 and therefore Q1001-2. This protects the RF pre-amplifier from excessive dissipation during transmit mode. A second 5-pole fixed-tuned bandpass filter provides additional filtering of the amplified signal. This filter configuration also provides steeper attenuation above its passband for best half-IF attenuation. 2.3 First Mixer The signal coming from the front-end is converted to the high-IF frequency of 10.7 MHz using a cross over quad diode mixer (U1051). The high-side injection signal (RXINJ) from the frequency synthesizer circuitry is filtered by a 7-pole low-pass filter (L1012-14 and associated circuitry) which removes second harmonic content from the injection signal and improves half-IF rejection. The 50- ohm output of the first mixer is applied to the input of the high-IF circuit block. 2.4 High Intermediate Frequency (IF) and Blanker Switches The first mixer IF output signal (IF) is applied to a diplexer network consisting of L1101, L1111 and associated components. This network has three functions: it terminates the mixer output at frequencies other than 10.7 MHz into 51-ohm resistor R1101; it matches the 50-ohm mixer output to the first IF amplifier (Q1101) input; and it provides bandpass filtering at 10.7 MHz to prevent the 5.35 MHz half-IF component of the mixer output from creating a second harmonic at 10.7 MHz in Q1101, which degrades half-IF rejection. The IF amplifier Q1101 uses ac and dc feedback to stabilize gain and quiescent current (approximately 28 mA). Operating voltage is from the regulated 9.3V supply (9V3). Its output is applied to a 10.7 MHz ceramic filter FL1101 which has a 3 dB bandwidth of 270 kHz and provides a time delay of 2.6 usec. This delay allows enough time for the “Extender” to respond to impulse noise present at the input of Q1101 and operate the blanker switches Q1102 and Q1103, muting the IF signal for the duration of the noise pulse. L1104 and L1105 also provide additional selectivity and time delay. Operation of the “Extender” circuit is explained in Section 8.5 below. When the blanker switches turn “on” to mute the IF signal, they momentarily change the impedance of resonant circuits L1104 and L1105 from high to very low. This abrupt impedance change, if
2-4THEORY 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. Q1104 has unity voltage gain in this configuration. Crystal filters FL1102 and FL1103 are 2-pole, 10.7 MHz units configured to provide an overall 4- pole response having a 3 dB bandwidth of approximately 12 kHz. The output is amplified by second IF amplifier Q1106 and applied to the low-IF circuitry, pin 1 of IF IC (U1103). A dual hot carrier diode (D1101) limits the amplifier output voltage swing to prevent overdriving the IF IC at RF input levels above -27 dBm. 2.5 Low Intermediate Frequency (IF) and Receiver Back End The 10.7 MHz high-IF signal from the second IF amplifier feeds the IF IC (U1103) at pin1. Within the IF IC, the 10.7 MHz high -IF signal mixes with the 10.245 MHz second local oscillator (2nd LO) to produce the low-IF signal at 455 kHz. The 2nd LO frequency is determined by crystal Y1101. The low -IF signal is amplified and filtered by external pairs of 455 kHz ceramic filters (FL1105 and FL1107 for 20 kHz channel spacing, or FL1104 and FL1106 for 12.5 kHz channel spacing). Selection of the appropriate filter pair is accomplished by U1101 and U1102, controlled by the BWSELECT line from pin 48 of the synthesizer IC U1201. The filtered output from the ceramic filters is applied to the limiter input pin of the IF IC (pin 14). The IF IC contains a quadrature detector using a ceramic phase-shift element (Y1102) to provide audio detection. Internal amplification provides an audio output level of 120 mV rms (at 60% deviation) from U1103 pin8 (AUDIOOUT) which is fed to the ASFIC_CMP (U0221) pin 2 (part of the Controller circuitry). A received signal strength indicator (RSSI) signal is available at U1103 pin 5, having a dynamic range of 70 dB. The RSSI signal is interpreted by the microprocessor (U0101 pin 63) and in addition is available at accessory connector J0501-15. 2.6 “Extender” (Noise Blanker) The 10.7 MHz output from the first mixer, which is present at the input of first IF amp Q1101, is also routed to the input of the “Extender” (noise blanker) circuitry and amplified by FET Q1610. The high input impedance of the FET stage minimizes loading of the signal in the receiver path. The output of Q1610 is further amplified by U1601, which is a wide-bandwidth, high gain differential amplifier (used in a single-ended configuration) incorporating an AGC gain control input. This gain block provides linear amplification of the instantaneous amplitude of the 10.7 MHz signal at the first mixer output. The output of U1601 is coupled to biased-detector Q1603. The bias is set so that noise impulses of a sufficient amplitude cause Q1603 to conduct. The following stages (Q1604 through Q1606) provide additional gain and pulse shaping which slows the turn-on and turn-off waveform applied to IF blanker switches Q1102 and Q1103. The result is that, for each noise impulse, the IF signal is smoothly ramped off and then on again, preventing the pulse from reaching the narrow IF selectivity, where ringing would cause an objectionable spike at the detector of a much longer duration than the original impulse. If the repetition rate of noise impulses is so rapid that the noise blanker can no longer blank them individually, as indicated by a large increase in high-frequency content at the output of Q1604, stage Q1607 amplifies this level and turns on level detector Q1609. Its output is highly filtered into a DC voltage level which is proportional to the repetition rate of the noise impulses, and this is applied to the AGC input pin 5 of U1601, reducing its gain and therefore the amount of noise pulses which are detected and processed.