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Johnson DM3474 Service Manual

Uhf high specification data module transceiver
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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.

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  • 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 3 Copyright© 1998 by the Johnson Data Telemetry Corporation. The Johnson Data Telemetry Corporation designs and manufactures radios and radio modems to serve a wide variety of data communication needs. The Johnson Data Telemetry Corporation produces equipment for the fixed data market including SCADA systems for utilities, petrochemical, waste and fresh water management markets and RF boards for OEM applications in the Radio Frequency Data Capture market.

  • Page 5: Table Of Contents

    DM3474 SYNTHESIZER DATA PROTOCOL ........
  • Page 6 TABLE OF CONTENTS RECEIVER CIRCUIT DESCRIPTION ............4-8 HELICAL FILTER (Z201), RF AMPLIFIER (Q201) .
  • Page 7 TABLE OF CONTENTS SCHEMATICS AND COMPONENT LAYOUTS VCO COMPONENT LAYOUT ..............8-2 TRANSCEIVER COMPONENT LAYOUT-COMPONENT SIDE VIEW .
  • Page 8 TABLE OF CONTENTS This page intentionally left blank.

  • Page 9: General Information

    Versions of the 3474 covered in this manual are 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 loading circuitry. 1.2.2 DM3474 SYNTHESIZER PROGRAMMING The DM3474 requires customer supplied circuitry to load the synthesizer with channel information.

  • Page 10: Part Number Breakdown

    GENERAL INFORMATION 1.4 PART NUMBER BREAKDOWN The following is a breakdown of the part number used to identify this transceiver: 242-3474 - X Y Z 0 = Base 2 = Portable 1 = 12.5 kHz BW 2 = 20 kHz BW 3 = 25 kHz BW 8 = 12.5 kHz BW * 9 = 25 kHz BW *...

  • Page 11: Product Warranty

    FAX Machine - Cust Serv(507) 835-6969 You can contact the Customer Service Department by mail or email. Please include any information that may help solve your problem. The mailing or email addresses are: Johnson Data Telemetry Corporation Customer Service Department 299 Johnson Avenue P.O.

  • Page 12: If A Problem Arises

    1.9.1 FACTORY REPAIR Component level repair is not recommended on the DM3474 Transceiver. Surface mount technology is used to install many components that require specialized training and equipment to service board level components.

  • Page 13: General Specifications

    -30° to +60° C (-22° to +140° F) Maximum Dimensions 2.83" L (7.19 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 ±1.5 PPM Frequency Stability 0.45 µV...
  • Page 14 GENERAL INFORMATION 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 ±1.5 dB from DC to 5 kHz (reference to 1 kHz) Audio Response Programmable to ±1 dB at the RF band edges via J201, pin 14.

  • Page 15: Installation

    Performance tests are located in Section 6.2. 2.2 INTERFACING WITH DATA EQUIPMENT 2.2.1 DM3474 ONLY Connector J201 on the data transceiver PC board provides the interface with the data equipment. This is a 14- pin female connector with .025"...
  • Page 16 INSTALLATION Pin 11 (Carrier Detect) - This output is not used at this time. Pin 12 (RSSI Output) - The RSSI (Receive Signal Strength 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 modulation signal of 1 kHz at 60% of maximum deviation.

  • Page 17: Programming

    The information in Section 3.2 describes synthesizer programming protocol. This information can be used as a basis for designing the synthesizer programming hardware and software required. 3.2 DM3474 SYNTHESIZER DATA PROTOCOL Programming of the dividers and the charge pumps are performed on a 3-line bus; SYNTH ENABLE, SYNTH DATA, AND SYNTH CLK.

  • Page 18: B-Word

    PROGRAMMING 3.2.2 B-WORD The B-Word is 24-bits long (see Figure 3-2). It contains the Address, Charge Pump setting factor (CN), Binary Acceleration factors (CK, CL), and Prescaler Type (PR). The Charge Pump Current setting (CN) could be changed on a channel-by-channel basis for ultimate rejection of the Fraction N spurious responses close into the carrier frequency.
  • Page 19 PROGRAMMING NM1 and NM2 are calculated as follows: N = (NM1 + 2) x 64 + NM2 x 65 Where: N = total division ratio NM1 = Number of main divider cycles when prescaler modulus equals 64 NM2 = Number of main divider cycles when prescaler modulus equals 65 Example: Calculate NM1 and NM2 to Receive 454.500 MHz.
  • Page 20 PROGRAMMING Figure 3-2 B-WORD Figure 3-3 A-WORD Part No. 001-3474-002...

  • Page 21: Serial Input Word Format

    PROGRAMMING Figure 3-4 SERIAL INPUT WORD FORMAT Part No. 001-3474-002...

  • Page 22: Receive To Transmit Sequence

    PROGRAMMING 3.3 RECEIVE TO TRANSMIT SEQUENCE Refer to Figure 3-5. 1. Synthesizer is loaded (B and A 24-Bit words or one long 32-bit A-Word). 2. The state of the 5RCL line does not have to be changed until the last bit is sent. However, RX will cease as soon as it is changed.

  • Page 23: Transmit To Receive Sequence

    PROGRAMMING 3.4 TRANSMIT TO RECEIVE SEQUENCE Refer to Figure 3-6. 1. 7.5 TX is turned OFF. For best TX adjacent channel power performance this could be shaped. 2. The synthesizer load process could begin slightly before, but when the last bit is strobed in the synthesizer it will become unlocked.
  • Page 24 PROGRAMMING This page intentionally left blank. Part No. 001-3474-002...

  • Page 25: Circuit Description

    SECTION 4 CIRCUIT DESCRIPTION 4.1 GENERAL 4.1.1 INTRODUCTION The main subassemblies of this transceiver are the RF board, VCO board, and TCXO. A block diagram of the transceiver is located in Figure 4-1. The VCO board is enclosed by a metal shield and soldered directly to the RF board. The VCO is not serviceable.

  • Page 26: Synthesizer

    CIRCUIT DESCRIPTION 4.1.4 TRANSMITTER The transmitter produces a nominal RF power output of 2W adjustable to 500 mW (-XX0). Frequency modulation of the transmit signal occurs in the synthesizer. Transmit audio processing circuitry is contained in the customer-supplied equipment. 4.2 SYNTHESIZER 4.2.1 INTRODUCTION A block diagram of the synthesizer is shown in Figure 4-1 and a block diagram of Synthesizer IC U801 is shown in Figure 4-2.

  • Page 27: Data Transceiver Block Diagram

    CIRCUIT DESCRIPTION MIXER 52.95 MHz U221 BUFFER CRYSTAL FILTER IF AMP IF / 450 kHz FILTER RF BPF RF AMP RF BPF RSSI Z201 Q201 Z202 Q222 Z221/Z222 Q221 U241 RX AUDIO 2nd LO AMP 1st LO AMP RECEIVER Q301 Q401 U251 ANTENNA...

  • Page 28: U801 Synthesizer Block Diagram

    CIRCUIT DESCRIPTION CLOCK DATA SERIAL INPUT + PROGRAM LATCHES V DD STROBE FMOD PRESCALER 64/65/72 FRACTIONAL MAIN DIVIDERS MODULUS PRESCALER ACCUMULATOR CONTROL TEST NORMAL OUTPUT CHARGE MAIN PUMP PHASE DETECTOR SPEED-UP OUTPUT MAIN CHARGE REFERENCE PUMP SELECT EM+EA INTEGRAL REFERENCE DIVIDER OUTPUT CHARGE PUMP...

  • Page 29: Voltage-Controlled Oscillator

    CIRCUIT DESCRIPTION 4.2.2 VOLTAGE-CONTROLLED OSCILLATOR Oscillator (Q850) The VCO is formed by Q850, several capacitors and varactor diodes, and a ceramic resonator. It oscillates at the transmit frequency in transmit mode and first injection frequency in the receive mode (approximately 450 MHz in transmit and 500 MHz in receive).

  • Page 30: Vco And Reference Oscillator Modulation

    CIRCUIT DESCRIPTION 4.2.3 VCO AND REFERENCE OSCILLATOR MODULATION Both the VCO and reference oscillator (TCXO) are modulated in order to achieve the required frequency response. If only the VCO was modulated, the phase detector in U801 would sense the frequency change and increase or decrease the VCO control voltage to counteract the change (especially at the lower audio frequencies).

  • Page 31: Synthesizer Integrated Circuit (U801)

    CIRCUIT DESCRIPTION When J201, pin 4 is high in receive, Q834 is turned off, Q101 is turned on and the collector voltage goes low. A low on the base of Q102 turns the transistor on and the regulated +5.5V on the emitter is on the collector for the receive circuitry.

  • Page 32: Receiver Circuit Description

    CIRCUIT DESCRIPTION 4.3 RECEIVER CIRCUIT DESCRIPTION 4.3.1 HELICAL FILTER (Z201), RF AMPLIFIER (Q201) Capacitor C201 couples the receive signal from the antenna switch to helical filter Z201. (The antenna switch is described in Section 4.4.5.) Z201 is a bandpass filter tuned to pass only a narrow band of frequencies to the receiver.

  • Page 33: Second Lo Amp/Tripler (Q401), Second If Filter (Q901)

    CIRCUIT DESCRIPTION 4.3.4 SECOND LO AMP/TRIPLER (Q401), SECOND IF FILTER (Q901) The input frequency to Q401 is 17.5 MHz from TCXO Y801 coupled through C402. Bias for Q401 is provided by R401, R402, R403 and R404. C403, C404 decouple RF from the amplifier. L401, L402, C405, C406 and C407 pass the third harmonic of the input (52.5 MHz) to U241, pin 1.

  • Page 34: Transmitter Circuit Description

    CIRCUIT DESCRIPTION Second IF Filter The output of the internal double-balanced mixer is the difference between 52.95 MHz and 52.5 MHz which is 450 kHz. This 450 kHz signal is fed out on pin 3 and applied to second IF filters Z241 and Z242. These filters have passbands of 9 kHz (12.5 kHz BW), 15 kHz (20 kHz BW) or 20 kHz (25 kHz BW) at the -6 dB points and are used to attenuate wideband noise.

  • Page 35: Pre-Driver (Q501), Driver (Q521)

    CIRCUIT DESCRIPTION 4.4.2 PRE-DRIVER (Q501), DRIVER (Q521) Pre-driver Q501 is biased class A by R501 and R502 and R506. L501 and C502 match Q501 to Q851. C520 and C508 bypass RF from the DC line, and R503 provides supply voltage isolation. R507 ties the +7.5V supply to the circuit for high power applications and R508 ties the circuit to +5V for low power applications.
  • Page 36 CIRCUIT DESCRIPTION C567, L566, and C570 form a discrete quarter- wave line. When CR561 is forward biased, this quarter-wave line is effectively AC grounded on one end by C570. When a quarter-wave line is grounded on one end, the other end presents a high impedance to the quarter-wave frequency.

  • Page 37: Servicing

    SECTION 5 SERVICING 5.1 GENERAL 5.1.1 PERIODIC CHECKS This transceiver should be put on a regular maintenance schedule and an accurate performance record maintained. Important checks are receiver sensitivity and transmitter frequency, modulation, and power output. A procedure for these and other tests is located in Section 6. It is recommended that transceiver performance be checked annually even though periodic checks are not required by the FCC.

  • Page 38: Reference Oscillator

    SERVICING NOTE: The user-supplied circuitry must disable the transmitter and receiver when an out-of-lock condition is indicated. When the VCO is unlocked, the inputs to the phase detector are usually not in phase (see Section 4.1.2). The phase detector in U801 then causes the VCO control voltage to go to the high or low end of its operating range.

  • Page 39: Receiver Servicing

    SERVICING 5.3 RECEIVER SERVICING To isolate a receiver problem to a specific section, refer to the troubleshooting flowchart in Figure 5-1. Tests referenced in the flowchart are described in the following information. NOTE: Supply voltages are provided by the user. 5.3.1 SUPPLY VOLTAGES AND CURRENT Measure the supply voltages on the following pins at interface connector J201: Pin 4 - 5.0V DC Receive...

  • Page 40: Rf Amplifier (Q201) And First Mixer (Q221)

    SERVICING Figure 5-1 RECEIVER SERVICING FLOWCHART 5.3.3 RF AMPLIFIER (Q201) AND FIRST MIXER (Q221) Refer to the schematic diagram for signal levels and test points for measuring levels. 5.3.4 RF AND IF AMPLIFIERS, FIRST MIXER Check the DC voltages shown on the schematic diagram. If they are normal, inject a signal at the input and output of each stage using a .01 µF coupling capacitor.

  • Page 41: Transmitter Servicing Flowchart

    SERVICING Pin 2 - 7.5V DC Pin 3 - 7.5V DC Pin 4 - 0.0V 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 mA Pin 3 - 250 mA...
  • Page 42 SERVICING This page intentionally left blank. Part No. 001-3474-002...

  • Page 43: Alignment Procedure And Performance Tests

    SECTION 6 ALIGNMENT PROCEDURE AND PERFORMANCE TESTS 6.1 GENERAL Receiver or transmitter alignment may be necessary if repairs are made that could affect tuning. Alignment points diagrams are located in Figure 6-3 or component layouts are located in Section 8. Fabricate test cables by referring to Section 2.2, Interfacing with Data Equipment.

  • Page 44: Low Power Alignment

    ALIGNMENT PROCEDURE AND PERFORMANCE TESTS 6. Adjust R542 clockwise for 2.30V DC (+0/-0.1V DC). 7. Readjust C553 counterclockwise for minimum current. 8. Tune C527 clockwise for maximum power. 9. Tune C553 clockwise for 2.0W (±0.1W). Current should be less than 900 mA. (Power output should be 1.6-2.4W and current less than 900 mA from 403-512 MHz.) 10.

  • Page 45: Modulation Flatness Alignment

    ALIGNMENT PROCEDURE AND PERFORMANCE TESTS 6. Tune C553 clockwise for minimum power. 7. Adjust R542 for the required power level. 8. Tune C527 for power balance at frequencies which are as close as possible to ±5 MHz from the center of the channel frequency.

  • Page 46: Receiver Alignment

    ALIGNMENT PROCEDURE AND PERFORMANCE TESTS Figure 6-2 RECEIVER TEST SETUP 6.2.5 RECEIVER ALIGNMENT C A U T I O N: Do not key the transmitter with the generator connected! Severe generator damage may result. 1. Connect the test setup shown in Figure 6-2. Adjust the power supply for +7.5V DC. 2.
  • Page 47 ALIGNMENT PROCEDURE AND PERFORMANCE TESTS NOTE: Maintain these deviation levels throughout the test when measuring AC levels, SINAD and % distortion. 3. Adjust L242 for 2.5V DC (±0.05V DC) at the receive audio output. 4. Set the RF signal generator level to -105 dBm, “unmodulated”. 5.

  • Page 48: Alignment Points Diagram

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

  • Page 49: Parts List

    SECTION 7 PARTS LIST 023-3474-515 SYMBOL PART DESCRIPTION NUMBER NUMBER A 801 FINISHED 450-466 VCO(M9 023-3474-540 C 101 68pF 5% NPO 0603 610-3674-680 C 102 68pF 5% NPO 0603 610-3674-680 C 103 68pF 5% NPO 0603 610-3674-680 C 104 68pF 5% NPO 0603 610-3674-680 C 105 68pF 5% NPO 0603...
  • Page 50 PARTS LIST SYMBOL PART DESCRIPTION NUMBER NUMBER C 229 .01MF X7R K 0603 CHPR 610-3675-103 C 230 .01MF X7R K 0603 CHPR 610-3675-103 C 232 1.5-5PF SMD CERAMIC 612-1602-001 C 235 .01MF X7R K 0603 CHPR 610-3675-103 C 241 .01MF X7R K 0603 CHPR 610-3675-103 C 242 .1UFD X7R J 1206 RL...
  • Page 51 PARTS LIST SYMBOL PART DESCRIPTION NUMBER NUMBER C 541 68pF 5% NPO 0603 610-3674-680 C 542 470pF 5% NPO 0603 610-3674-471 C 546 68pF 5% NPO 0603 610-3674-680 C 547 68pF 5% NPO 0603 610-3674-680 C 548 1.0UFD 16V SMD TANT RL 610-2625-109 C 549 .01MF X7R K 0603 CHPR...
  • Page 52 PARTS LIST SYMBOL PART DESCRIPTION NUMBER NUMBER C 838 68pF 5% NPO 0603 610-3674-680 C 839 .01MF X7R K 0603 CHPR 610-3675-103 C 840 .01MF X7R K 0603 CHPR 610-3675-103 C 841 68pF 5% NPO 0603 610-3674-680 C 842 .01MF X7R K 0603 CHPR 610-3675-103 C 844 1.0UFD 16V SMD TANT RL...
  • Page 53 PARTS LIST SYMBOL PART DESCRIPTION NUMBER NUMBER MP 801 CAN-VCO 3474 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 PC 001 PCB DL 3474 MAIN (MUL6) 035-3474-030...
  • Page 54 PARTS LIST SYMBOL PART DESCRIPTION NUMBER NUMBER R 301 3.3K OHM J 063W 0603 CHIP 669-0155-332 R 302 1.8K OHMS J 063W 0603 CHI 669-0155-182 R 303 180 OHMS J 063W 0603 CHIP 669-0155-181 R 304 470 OHMS J 063W 0603 CHIP 669-0155-471 R 401 10 OHMS J 063W 0603 CHIP...
  • Page 55 PARTS LIST SYMBOL PART DESCRIPTION NUMBER NUMBER R 846 18 OHMS J 063W 0603 CHIP 669-0155-180 R 847 18 OHMS J 063W 0603 CHIP 669-0155-180 R 848 1.5K OHM J 063W 0603 CHIP 669-0155-152 R 851 150 OHMS J 063W 0603 CHIP 669-0155-151 R 852 39 OHM J 0603 CHIP/R...
  • Page 56 PARTS LIST SYMBOL PART DESCRIPTION NUMBER NUMBER C 873 100pF 5% NPO 0603 610-3674-101 C 874 3.3pF +/-.1pF NPO 0603 610-3673-339 C 876 8.2pF +/-.1pF NPO 0603 610-3673-829 C 877 1pF +/-.1pF NPO 0603 610-3673-109 C 878 10PF NPO J 0805 CHP RL 610-3601-100 CR 850 SOT PIN SW DIODE T/RL...
  • Page 57 PARTS LIST EP 200 MINI CER CRY PIN INSUL 010-0345-280 J 201 14P SGL ROW RCPT.1CNTR 615-7110-214 J 501 STR TERM PCB 615-3013-030 L 222 1+/-6%UH VAR. IND. 5MM 642-1012-015 L 224 1+/-6%UH VAR. IND. 5MM 642-1012-015 MP 801 CAN-VCO 3474 017-2225-751 MP 802 TOP SHIELD 3474 XMIT...
  • Page 58 PARTS LIST 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.1CNTR 615-7110-214 J 501 STR TERM PCB 615-3013-030 L 222 1+/-6%UH VAR. IND. 5MM 642-1012-015 L 224 1+/-6%UH VAR. IND. 5MM 642-1012-015 MP 801 CAN-VCO 3474...
  • Page 59 SECTION 8 SCHEMATIC AND COMPONENT LAYOUTS TRANSISTOR AND DIODE BASING REFERENCE TABLE TRANSISTORS Part Number Basing Diagram Identification 676-0003-604 3604 676-0003-616 676-0003-621 676-0003-634 676-0003-636 676-0003-640 676-0003-651 676-0006-450 676-0013-701 DIODES 623-1504-001 623-1504-002 623-1504-023 623-5005-020 623-5005-022 INTEGRATED CIRCUITS Part No. 001-3474-002...

  • Page 60: Schematics And Component Layouts

    SCHEMATICS AND COMPONENT LAYOUTS Figure 8-1 VCO COMPONENT LAYOUT (COMPONENT SIDE VIEW) Part No. 001-3474-002...

  • Page 61: Transceiver Component Layout (Component Side View)

    SCHEMATICS AND COMPONENT LAYOUTS Figure 8-2 TRANSCEIVER COMPONENT LAYOUT (COMPONENT SIDE VIEW) Part No. 001-3474-002...

  • Page 62: Transceiver Component Layout (Opposite Component Side View)

    SCHEMATICS AND COMPONENT LAYOUTS Figure 8-3 TRANSCEIVER COMPONENT LAYOUT (OPPOSITE COMPONENT SIDE VIEW) Part No. 001-3474-002...
  • Page 63 SCHEMATICS AND COMPONENT LAYOUTS Figure 8-4 DM-3474 SCHEMATIC Company Confidential Copyright 1998 Johnson Data Telemetry Corporation Part No. 001-3474-002...
  • Page 64 SCHEMATICS AND COMPONENT LAYOUTS This page intentionally left blank. Part No. 001-3474-002...

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