TABLE OF CONTENTS GENERAL INFORMATION SCOPE OF MANUAL EQUIPMENT DESCRIPTION. .. GENERAL nnn l= DM3474 SYNTHESIZER PROGRAMMING . TRANSCEIVER IDENTIFICATION . PART NUMBER BREAKDOWN .. ACCESSORIES FACTORY CUSTOMER SERVICE PRODUCT WARRANTY REPLACEMENT PARTS. FACTORY RETURNS INSTALLATION PER-INSTALLATION CHECKS INTERFACING WITH DATA EQUIPMENT. DM3474 ONLY PROGRAMMING INTRODUCTION DM3474 SYNTHESIZER DATA PI D-WORD . .
TABLE OF CONTENTS SECOND MIXER/DETECTOR (U241) TRANSMITTER CIRCUIT DESCRIPTION PER-DRIVER (Q501), DRIVER (Q521). -5V POWER CONTROL SUPPLY FINAL (Q541), POWER CONTROL (U542) . ANTENNA SWITCH (CR561, CR562) SERVICING GENERAL. . PERIODIC CHECKS SURFACE-MOUNTED COMPONENTS. SCHEMATIC DIAGRAMS AND COMPONENT LAYOUTS REPLACEMENT PARTS LIST... OTC MODULE NOT SERVICEABLE SYNTHESIZER SERVICING .. INTRODUCTION REFERENCE OSCILLATOR CO. SYNTHESIZER (US01). RECEIVER SERVICING .
1-1 LIST OF FIGURES DM3474 INTERFACE CABLE. ea 2:2 D-WORD 3-2 B-WORD 3-2 A-WORD .33 SERIAL INPUT WORD FORMAT cocaine .3-3 RX TO TX TIMING DIAGRAM TIMING DIAGRAM .34 DATA TRANSCEIVER BLOCK DIAGRAM . .42 U801 SYNTHESIZER BLOCK DIAGRAM. U241 BLOCK DIAGRAM... RECEIVER SERVICING FLOWCHART TRANSMITTER SERVICING FLOWCHART .. TRANSMITTER TEST SETUP nets ova rsa . 61 RECEIVER TEST .62 ALIGNMENT POINTS DIAGRAM . 6-4 VCO COMPONENT LAYOUT (COMPONENT SIDE cen .81 TRANSCEIVER COMPONENT LAYOUT (COMPONENT SIDE VIEW) .
ERs TRACTOR Ee TAA ASTRAL TA The following are general specifications intended for use in testing and servicing this transceiver. For current advertised specifications, refer to the specification sheet available from the Marketing Department. Specifications are subject to change without notice.
SECTION 2 INSTALLATION 2.1 PER-INSTALLATION CHECKS Field alignment should not be required before the 3474 is installed. However, it is still good practice to check the performance to ensure that no damage occurred during shipment. Performance tests are located in Section 6.2. 2.2 INTERFACING WITH DATA EQUIPMENT 22.1 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" square pins on 0.
SECTION 4 CIRCUIT DESCRIPTION 4.1 GENERAL 4.1.1 INTRODUCTION The main sub assemblies of this transceiver are the RF board, VCO board, OTC. 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. The 3474 is available with a reference oscillator stability of £1.5 PPM. The OTC (Temperature Compensated Crystal Oscillator) is soldered directly to the RF board. 4.
PROGRAMMING The Fractional-N increment (NF) is a 3-bit word that is channel dependent. NF is used to program the sub-channels below the 50 kHz Loop Reference frequency. FCM = 50 kHz and if MOD = 8, then the Fractional-N increment is: 50 kHz + 8 =6.25 kHz To program an 18.75 kHz channel: NF = 18.75 kHz + 6.
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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 SR CL line does not have to be changed until the last bit is sent. However, RX will cease as soon as it is changed. 3. The SYNTH ENABLE line should be held HIGH for 2 to 3 milliseconds after the last word is sent. This puts the frequency synthesizer in a SPEEDUP MODE and slightly improves lock times. 4.
jow impedance to RF; and when it is reverse biased, it presents a very high impedance. The capacities leg is switched in when in transmit and out when in receive. ‘When 1201, 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. With a low on the base of Q831 the transistor is off and the collector is high.
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Limiter-Amplifier The output of 2241/7242 is applied to a limiter amplifier circuit in U241. This circuit amplifies the 450 kHz signal and any noise present; then limits this signal to a specific value. When the 450 kHz signal level is high, noise pulses tend to get clipped off by the limiter; however, when the 450 kHz signal level is fow, the noise passes through. C242, C243 decouple the 450 kHz signal. Quadrature Detector From the limiter stage the signal is fed to the quadrature detector.
CIRCUIT DESCRIPTION The -2V applied to the VCO is derived from the OTC frequency that is amplified by Q833, rectified by CR831 and filtered by CB, C845, CB and C847 on the RF board. The VCO frequency is modulated using a similar method. The transmit candidate signal is applied across var actor diode CR852 which varies the VCO frequency at an audio rate. Series capacitors C856/ C870 set the amount of deviation produced along with CR853 and C858.
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.
CIRCUIT DESCRIPTION 4.32 MIXER (U221), FIRST LO AMPLIFIER Q301) First mixer U221 mixes the receive frequency with the first injection frequency to produce the 52.95 MHz first IF. Since high-side injection is used, the injection frequency is 52.95 MHz above the receive frequency. The RF signal is coupled to the mixer through C211. The first injection frequency from the VCO is coupled to the first local oscillator amplifier Q301 through C301. L301 and C302 match Q301 to the VCO.
5.3.3 RF AMPLIFIER (Q201) AND FIRST MIXER Qzz1) Refer to the schematic diagram for signal levels and test points for measuring levels. 53.4 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 uF coupling capacitor. 1f the stage is producing gain, the injection level on the input of a stage should be less than that required on the output to produce the same SIN AD at the receive output.
CIRCUIT DESCRIPTION The low-pass filter consists of L561, C561, L562, C562, L563, C563 and L564. The filter attenuates spurious frequencies occurring above the transmit frequency band. The transmit signal is then fed through the antenna switch 10 antenna jack J501. 4.4.5 ANTENNA SWITCH (CR561, CR562) The antenna switching circuit switches the antenna to the receiver in the receive mode and the transmitter in the transmit mode. In the transmit mode, +7.
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 Figure 2-1. This cable should include power and ground, a transmit keying switch that shorts the keying line to ground, data input and data output.
SERVICING Control Voltage Check the DC voltage at C815 with a channel near the center of the band. If the VCO is locked on frequency, this should be a steady DC voltage near 3V. Ileitis not locked on frequency, it should be near the lower or upper end of its range (0V or 5.5V). Output Frequency Check the VCO frequency at R851. If the VCO is locked on frequency, it should be stable on the transmit channel frequency. If the VCO is not locked on frequency, the VCO control voltage is probably near OV or 5.5V.
2. Measure the receive current drain. (Typically current should be <80 mA.) 3. Preset tuning slugs of 10 the full clockwise position (slug in all the’ way). 4. Preset C232 to center position (slot in-line with axis of part). 5. Readjust 1.224 counterclockwise 2 turns. 6.2.6 IF AND AUDIO ADJUSTMENTS 1. Load the synthesizer with the channel frequency. 2. Set the RF signal generator for this frequency with a 1 kHz tone (modulated output shown below) ata level of -47 dBm (1000 pV) and inject into J501. 1.
SECTÁRIO 7 PARTA LISTA SÍMBOLO PAR NUMERAR DESCRITIVO NUMERAR HIGH-SPEC DATA TRANSCREVER PAR NO.
ALIGNMENT PROCEDURE AND PERFORMANCE TESTS 6.2.3 LOW POWER ALIGNMENT 1. Connect the test setup shown in Figure 6-1. 2. Load the synthesizer with the center channel frequency. 3. Connect a voltmeter to the junction of R542/R543. 4. Adjust R542 clockwise for -1.5V DC DC). 5. Tune C527 clockwise for maximum power. 6. Tune C533 clockwise for minimum power. 7. Adjust R542 for the required power level. 8.
ALIGNMENT PROCEDURE AND PERFORMANCE TESTS R543/R542 1051 & £232 ) al oar R8Q7/R255% = = wo is Figure 6-3 ALIGNMENT POINTS DIAGRAM January 1996 Part No, 001-3474-001 6-4
SYMBOL PART NUMBER DESCRIPTIO NUMBER Z202 443 MHz heli cal filtr SMD 532-1005-042 (435-451 MHz) Z 202 459 MHz heli cal filtr SMD ~~ 532-1005-044 {450-466 MHz) Z202 472 MHz heli cal filtr SMD 532-1005-045 (464-430 MHz) Z221 52.95 MHz 4-pole § kHz BW 532-0009-011 (12.5 kHz sandwich) Z221 5295 MHz 4-opie 15 kHz BW 532-0009-009 (20 kHz and 25 kHz sandwich) Z222 52.95 MHz 4-pole § kHz BW 532-0009-011 (12.5 kHz sandwich) Z222 52.
PARTS LIST SYMBOL NUMBER DESCRIPTION 1.2 pF £0.1% NPO 0603 (464-480 MHz) 1.8 pF £0.1% NPO 0603 (480-496 MHz) 1 pF 0.1% NPO 0603 100 pF +5% NPO 0603 100 pF +5% NPO 0603 33 pF £0.1% NPO 0603 (403-419 MHz) 3.3 pF +0.1% NPO 0603 (419-435 MHz) 3.3 pF £0.1% NPO 0603 (435-496 MHz) 10 pF +0.1% NPO 0603 (403-419 MHz) 9.1 pF 30.1% NPO 0603 (419-435 MHz) 8.2 pF +0.1% NPO 0603 (435.496 MHz) 1.2 pF £0.1% NPO 0603 (403-435 MHz) 1 pF 0.1% NPO 0603 (435-496 MHz) 10 pF £0.