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Johnson DM3474, Service Manual

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Johnson DM3474 Service Manual Download Page 14

GENERAL INFORMATION

1-6

Part No. 001-3474-002

Duty Cycle 

50%, 60 seconds maximum transmit

Transmitter Attack Time

< 7 ms (dependent on synthesizer implementation)

Spurious and Harmonic FM

-37 dBm

FM Hum and Noise

-40 dB 12.5 kHz, -45 dB 25 kHz

Audio Response

±

1.5 dB from DC to 5 kHz (reference to 1 kHz) 

Programmable to 

±

1 dB at the RF band edges via J201, pin 14.

Data Input Impedance

100k ohm

Modulation Response

±

1 dB from DC to 5 kHz (reference to 1 kHz)

Current Drain

< 800 mA at 2W, +7.5V DC

Summary of Contents for DM3474

Page 1: ...HIGH SPECIFICATION DATA TRANSCEIVER PART NO 242 3474 XX0 Second Printing August 1998 Part No 001 3474 002 8 98 Printed in U S A...

Page 2: ......

Page 3: ...FCC rules Operation is subject to the condition that this device does not cause harmful interference In addition changes or modification to this equipment not expressly approved by Johnson Data Telem...

Page 4: ......

Page 5: ...ECKS 2 1 2 2 INTERFACING WITH DATA EQUIPMENT 2 1 DM3474 ONLY 2 1 3 PROGRAMMING 3 1 INTRODUCTION 3 1 3 2 DM3474 SYNTHESIZER DATA PROTOCOL 3 1 D WORD 3 1 B WORD 3 2 A WORD 3 2 3 3 RECEIVE TO TRANSMIT SE...

Page 6: ...NENTS 5 1 SCHEMATIC DIAGRAMS AND COMPONENT LAYOUTS 5 1 REPLACEMENT PARTS LIST 5 1 TCXO MODULE NOT SERVICEABLE 5 1 5 2 SYNTHESIZER SERVICING 5 1 INTRODUCTION 5 1 REFERENCE OSCILLATOR 5 2 VCO 5 2 SYNTHE...

Page 7: ...6 TX TO RX TIMING DIAGRAM 3 7 4 1 DATA TRANSCEIVER BLOCK DIAGRAM 4 3 4 2 U801 SYNTHESIZER BLOCK DIAGRAM 4 4 4 3 U241 BLOCK DIAGRAM 4 9 5 1 RECEIVER SERVICING FLOWCHART 5 4 5 2 TRANSMITTER SERVICING FL...

Page 8: ...TABLE OF CONTENTS iv This page intentionally left blank...

Page 9: ...indicated in Section 1 4 The 3474 has a frequency stability of 1 5 PPM see Section The number of channels that can be selected with the DM3474 model is determined by the customer supplied synthesizer...

Page 10: ...y of local and factory repair facilities Customer Service hours are 7 30 a m 4 30 p m Central Time Monday Friday From within the continental United States the Customer Service Department can be reache...

Page 11: ...ion that may help solve your problem The mailing or email addresses are Johnson Data Telemetry Corporation Customer Service Department 299 Johnson Avenue P O Box 1733 Waseca MN 56093 0514 support john...

Page 12: ...rge by calling Customer Service see Section 1 6 Describe the problem in the space provided and note any prior physical damage to the equipment Include a form in the shipping container with each unit Y...

Page 13: ...cm 2 19 W 5 56 cm 0 64 H 1 70 cm Weight w o Loader Bd 2 3 oz 65 g FCC Compliance DM3474 customer must apply RECEIVER Bandwidth 16 MHz Frequency Stability 1 5 PPM Sensitivity 12 dB SINAD 0 45 V RF Inpu...

Page 14: ...zer implementation Spurious and Harmonic FM 37 dBm FM Hum and Noise 40 dB 12 5 kHz 45 dB 25 kHz Audio Response 1 5 dB from DC to 5 kHz reference to 1 kHz Programmable to 1 dB at the RF band edges via...

Page 15: ...5V DC in transmit mode only Pin 4 5V DC Receive Control Line This input should be 5V DC in the receive mode only 0 3 V DC in Tx input impedance 10k ohms Pin 5 5V DC Continuous This voltage should be...

Page 16: ...rength Indicator output provides a voltage that increases in proportion to the strength of the RF input signal Pin 13 Rx Output The data output level is 600 1200 millivolts P P 200 400 mV RMS with a m...

Page 17: ...ed in the 3474 The 24 and 32 bit words contain one or four address bits depending on the address bits the data is latched into registers When the A word is loaded the data of these temporary registers...

Page 18: ...nimized far below the levels needed to make ETSI 70 dB adjacent channel RX or TX specifications Example Model 3474 530 is a 450 466 MHz transceiver 458 MHz TX CN 88 01011000 Binary 458 MHz RX CN 98 01...

Page 19: ...er modulus equals 64 NM2 Number of main divider cycles when prescaler modulus equals 65 Example Calculate NM1 and NM2 to Receive 454 500 MHz LO 454 5 52 95 507 45 MHz 52 95 MHz IF with High Side Injec...

Page 20: ...PROGRAMMING 3 4 Part No 001 3474 002 Figure 3 2 B WORD Figure 3 3 A WORD...

Page 21: ...PROGRAMMING 3 5 Part No 001 3474 002 Figure 3 4 SERIAL INPUT WORD FORMAT...

Page 22: ...d slightly improves lock times 4 After the last word is strobed in 7 milliseconds worst case should elapse before 7 5 TX is turned ON This allows the synthesizer to come within 1 kHz of the desired fr...

Page 23: ...be held high for 2 to 3 millisec onds It MUST NOT be left high as the synthesizer in the SPEEDUP mode has poor noise performance and would degrade the RX performance Figure 3 6 TX TO RX TIMING DIAGRAM...

Page 24: ...PROGRAMMING 3 8 Part No 001 3474 002 This page intentionally left blank...

Page 25: ...eive frequency The frequency of this oscillator is controlled by a DC voltage produced by the phase detector in synthesizer chip U801 Channels are selected by programming counters in U801 to divide by...

Page 26: ...gure 4 2 As stated previously the synthesizer output signal is produced by a VCO voltage controlled oscillator The VCO frequency is controlled by a DC voltage produced by the phase detector in U801 Th...

Page 27: ...LOCK ENABLE DATA CLOCK AMPLIFIER 5V T R PS NEG SUP RECEIVER TRANSMITTER SYNTHESIZER VCO BUFFER RSSI ANTENNA LOW PASS FILTER RF OUT RF BPF RF BPF U221 Z221 Z222 52 95 MHz Q222 IF 450 kHz FILTER Q521 Q...

Page 28: ...ONTROL 3 FMOD NF FB SERIAL INPUT PROGRAM LATCHES VDD TEST IN REF EM EA REFERENCE DIVIDER 2 2 2 MAIN MAIN PHASE DETECTOR REFERENCE SELECT 2 SM EM REFERENCE SELECT 2 SA SECONDARY PHASE DETECTOR EA AUXIL...

Page 29: ...e L851 and L854 and decoupling capacitor C854 The amount of frequency change produced by CR854 CR855 CR856 CR851 is controlled by series capacitor C853 The 2V applied to the VCO is derived from the TC...

Page 30: ...ween the VCO and receiver and transmitter C868 provides matching between the amplifiers Bias for Q853 is provided by R871 R872 and R874 Inductor L856 and capacitor C873 provide impedance matching on t...

Page 31: ...the tank circuit This decreases the resonant frequency of the tank circuit 4 2 8 SYNTHESIZER INTEGRATED CIRCUIT U801 Introduction Synthesizer chip U801 is shown in Figure 4 2 This device contains the...

Page 32: ...on frequency is 52 95 MHz above the receive frequency The RF signal is coupled to the mixer through C206 The first injection frequency from the VCO is coupled to the first local oscillator amplifier Q...

Page 33: ...e amplifier is coupled to U241 pin 1 by C241 and C410 and L404 provided low frequency decoupling 4 3 5 SECOND MIXER DETECTOR U241 Oscillator and Mixer As shown in Figure 4 3 U241 contains the second o...

Page 34: ...s at an audio rate as does the phase of the shifted input The detector which has no output with a 90 phase shift converts this phase shift into an audio signal L242 is tuned to provide maximum undisto...

Page 35: ...ER CONTROL U542 Q541 is biased for Class C operation The output is matched to the low pass filter by L541 C552 and several capacitors The supply voltage is isolated from RF by ferrite bead EP541 Power...

Page 36: ...nded on one end the other end presents a high impedance to the quarter wave frequency This blocks the transmit signal from the receiver C569 matches the antenna to 50 ohms in transmit and receive In t...

Page 37: ...re replaced to prevent damage to the component or PC board Surface mounted components should not be reused because they may be damaged by the unsoldering process 5 1 3 SCHEMATIC DIAGRAMS AND COMPONENT...

Page 38: ...t is operating properly 5 2 2 REFERENCE OSCILLATOR Check the signal at U801 pin 8 It should be 17 5 MHz at a level of approximately 1 5V P P If the TCXO module is defective it is not serviceable and m...

Page 39: ...ly line to the transceiver and the following maximum currents should be measured Pin 4 10 mA Pin 5 50 mA 5 3 2 MIXER DETECTOR U201 Data Output Using a 01 F coupling capacitor inject at U241 pin 16 a 5...

Page 40: ...C voltages shown on the schematic diagram If they are normal inject a signal at the input and output of each stage using a 01 F coupling capacitor If the stage is producing gain the injection level on...

Page 41: ...0V DC while transmitting Pin 5 5 0V DC Pin 6 2 5V DC Transmit In 1 5V P P max Place a DC ammeter in the supply line to the transceiver and the following maximum currents should be measured Pin 2 650...

Page 42: ...SERVICING 5 6 Part No 001 3474 002 This page intentionally left blank...

Page 43: ...AGE CHECK 1 Connect the test setup shown in Figure 6 1 Set the power supply for 7 5V DC 2 Load the synthesizer with the channel frequency see Section 3 2 3 Connect a DC voltmeter at the junction of R8...

Page 44: ...Power output should be 1 6 2 4W and current less than 900 mA from 403 512 MHz 10 Monitor the frequency with a frequency counter and adjust TCXO Y801 for the channel frequency 100 Hz Figure 6 1 TRANSMI...

Page 45: ...n analyzer high pass filtering off and no less than a 15 kHz low pass filter 3 Adjust R810 for a flat square wave on the oscilloscope 4 Inject a 1 kHz sine wave on J201 pin 6 biased at 2 5V DC at the...

Page 46: ...rent should be 80 mA 3 Preset tuning slugs of L222 L224 to the full clockwise position slug in all the way 4 Preset C232 to center position slot in line with axis of part 5 Readjust L224 counterclockw...

Page 47: ...generator frequency back to channel center at 47 dBm with standard deviation level 8 Adjust L224 for minimum distortion 9 Set the RF signal generator to 105 dBm unmodulated 10 Adjust L222 for peak RS...

Page 48: ...ALIGNMENT PROCEDURE AND PERFORMANCE TESTS 6 6 Part No 001 3474 002 Figure 6 3 ALIGNMENT POINTS DIAGRAM R509...

Page 49: ...C 116 01MF X7R K 0603 CHPR 610 3675 103 C 117 1 0UFD 16V SMD TANT RL 610 2625 109 C 118 68pF 5 NPO 0603 610 3674 680 C 119 68pF 5 NPO 0603 610 3674 680 C 131 1 0UFD 16V SMD TANT RL 610 2625 109 C 132...

Page 50: ...C 401 01MF X7R K 0603 CHPR 610 3675 103 C 402 01MF X7R K 0603 CHPR 610 3675 103 C 403 01MF X7R K 0603 CHPR 610 3675 103 C 404 01MF X7R K 0603 CHPR 610 3675 103 C 405 82pF 5 NPO 0603 610 3674 820 C 40...

Page 51: ...10 3674 680 C 572 01MF X7R K 0603 CHPR 610 3675 103 C 573 1 0UFD 16V SMD TANT RL 610 2625 109 C 801 01MF X7R K 0603 CHPR 610 3675 103 C 802 01MF X7R K 0603 CHPR 610 3675 103 C 803 01MF X7R K 0603 CHPR...

Page 52: ...615 7110 214 J 501 STR TERM PCB 615 3013 030 L 201 INDUCT LL2012 F8 2N 0805 642 9003 826 L 202 22 NHY0805 SMD 10 INDUCT 642 9003 227 L 222 1 6 UH VAR IND 5MM 642 1012 015 L 223 0 82 MHY SMD INDUCTOR 6...

Page 53: ...4 R 131 100k OHMS J 063W 0603 CHI 669 0155 104 R 201 47 OHMS J 063W 0603 CHIP 669 0155 470 R 202 2 7K OHM J 063W 0603 CHIP 669 0155 272 R 203 750 OHM RES J 063W 0603 C 669 0155 751 R 204 330 OHMS J 06...

Page 54: ...155 100 R 551 10 OHMS J 063W 0603 CHIP 669 0155 100 R 562 RES 270R 0 75W 5 L07 669 0135 271 R 564 47K OHMS J 063W 0603 CHIP 669 0155 473 R 801 10K OHMS J 063W 0603 CHIP 669 0155 103 R 802 10K OHMS J 0...

Page 55: ...261 MC33172D SO8 OP AMP 644 2019 017 U 801 FRACTIONAL N SYNTHESIZER 644 3954 027 Y 801 17 5 MHZ TCXO 1 5 PPM 618 7009 521 Z 201 SMD HEL FLTR 459 MHZ 3 PO 632 1005 044 Z 202 SMD HEL FLTR 459 MHZ 3 PO 6...

Page 56: ...1 Q 853 NPN TRANS NE85619 SC90 676 0003 651 R 851 10K OHMS J 063W 0603 C 669 0155 103 R 852 47K OHMS J 063W 0603 C 669 0155 473 R 853 47K OHMS J 063W 0603 C 669 0155 473 R 854 10 OHMS J 063W 0603 CH 6...

Page 57: ...4 015 Z 242 450 KHZ 9 KHZ BW CERAMIC 632 2004 015 023 3474 521 C 225 39pF 5 NPO 0603 610 3674 390 C 227 10pF 1pF NPO 0603 610 3673 100 EP 200 MINI CER CRY PIN INSUL 010 0345 280 J 201 14P SGL ROW RCPT...

Page 58: ...017 2225 751 MP 802 TOP SHIELD 3474 XMIT 017 2225 761 MP 803 SHIELD 3474 BOTTOM XMIT 017 2225 762 MP 804 3474 SHIELD BOTTOM SYNTH 017 2225 763 MP 806 XTAL FLTR SHIELD 3472 017 2225 699 R 230 1 8K OHM...

Page 59: ...REFERENCE TABLE TRANSISTORS Part Number Basing Diagram Identification 676 0003 604 2 3604 676 0003 616 1 26 676 0003 621 1 74 676 0003 634 1 3B 676 0003 636 1 R25 676 0003 640 3 676 0003 651 1 24 676...

Page 60: ...SCHEMATICS AND COMPONENT LAYOUTS 8 2 Part No 001 3474 002 Figure 8 1 VCO COMPONENT LAYOUT COMPONENT SIDE VIEW...

Page 61: ...SCHEMATICS AND COMPONENT LAYOUTS 8 3 Part No 001 3474 002 Figure 8 2 TRANSCEIVER COMPONENT LAYOUT COMPONENT SIDE VIEW...

Page 62: ...SCHEMATICS AND COMPONENT LAYOUTS 8 4 Part No 001 3474 002 Figure 8 3 TRANSCEIVER COMPONENT LAYOUT OPPOSITE COMPONENT SIDE VIEW...

Page 63: ...SCHEMATICS AND COMPONENT LAYOUTS 8 5 Part No 001 3474 002 Figure 8 4 DM 3474 SCHEMATIC Company Confidential Copyright 1998 Johnson Data Telemetry Corporation...

Page 64: ...SCHEMATICS AND COMPONENT LAYOUTS 8 6 Part No 001 3474 002 This page intentionally left blank...

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