Motorola Mtx Series Detailed Rev 6881088c46 E Manual
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Page 71
FMR-2045A-2December 26, 2003 VHF Theory of Operation: Frequency Generation Circuitry 71 Radio signal strength indicator, RSSI, a voltage signal, is used to drive Q3301 to saturation i.e. turned on. RSSI is produced by U3220 and is proportional to the gain of the RF amplifier and the input power to the radio. Resistors R3304 and R3305 are voltage dividers designed to turn on Q3301 at certain RSSI levels. In order to turn on Q3301 the voltage across R3305 must be greater or equal to the voltage across...
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December 26, 2003FMR-2045A-2 72VHF Theory of Operation: Synthesizer 7.4 Synthesizer (Refer to the VHF Synthesizer Schematic Diagram on page 82.) The Fractional-N Synthesizer uses a 16.8MHz crystal (Y3761) to provide a reference for the system. The LVFractN IC (U3701) further divides this to 2.1MHz, 2.225 MHz, and 2.4 MHz as reference frequencies. Together with C3761, C3762, C3763, R3761 and D3761, they build up the reference oscillator which is capable of 2.5ppm stability over temperatures of -30 to...
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FMR-2045A-2December 26, 2003 VHF Theory of Operation: Voltage-Controlled Oscillator (VCO) 73 7.5 Voltage-Controlled Oscillator (VCO) (Refer to the VHF Voltage-Controlled Oscillator Schematic Diagram on page 83.) Figure 7-5. VCO Block Diagram The VCOBIC (U3801) in conjunction with the Fractional-N synthesizer (U3701) generates RF in both the receive and the transmit modes of operation. The TRB line (U3801 pin 19) determines which oscillator and buffer will be enabled. A sample of the RF signal from the...
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December 26, 2003FMR-2045A-2 74VHF Theory of Operation: Voltage-Controlled Oscillator (VCO) The RF section of the VCOBIC(U3801) is operated at 4.54 V (VSF), while the control section of the VCOBIC and Fractional-N synthesizer (U3701) is operated at 3.3V. The operation logic is shown in Table 7-1. In receive mode, U3801 pin 19 is low or grounded. This activates the receive VCO by enabling the receive oscillator and the receive buffer of U3801. The RF signal at U3801 pin 8 is run through a matching...
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Chapter 8 VHF Circuit Board Layouts, Schematic Diagrams and Parts List 8.1 Notes For All Schematics and Circuit Boards * Component is frequency sensitive. Refer to the Electrical Parts List for value and usage. 1.Unless otherwise stated, resistances are in Ohms (k = 1000), and capacitances are in picofarads (pF) or microfarads (µF). 2.DC voltages are measured from point indicated to chassis ground using a Motorola DC multime- ter or equivalent. Transmitter measurements should be made with a 1.2 µH...
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December 26, 2003FMR-2045A-2 This Page Intentionally Left Blank 76VHF Circuit Board Layouts, Schematic Diagrams and Parts List: Notes For All Schematics and Circuit Boards
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Circuit Board/Schematic Diagrams and Parts List 77 FMR-2045A-2 December 26, 2003 8.2 Circuit Board/Schematic Diagrams and Parts List Figure 8-1. VHF (136-174MHz) Main Board Top Side PCB No. 8486473Z03 C502C505 C512 C513 Q502Q505 R505R506 VR501 123 5PB501 4 3 2 Y3204C521 C3225C3278 R3275 58 U3221 VR440 2 Y3202 Y3205 C3208 R3205 R3208 R3211 4C3206 L3200 L3203 123 5PB504VR444 43 2 Y3203 C3201 C3202 SH3203 2 3 4 56 Y3200123 5PB502 C522 B503B504 TP3701C523 123 5PB503 6 431 Y3761 C432 TP3702 C3706 C3710...
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78Circuit Board/Schematic Diagrams and Parts ListDecember 26, 2003FMR-2045A-2 Figure 8-2. VHF (136-174MHz) Main Board Bottom Side PCB No. 8486473Z03 C449 C458 C459C463 C466C4020C4021 E400 E401 E402E403 E404 E405 E406 1 7651 26 U409 C453 C456 L410 L411R409R411 R432 R457C431 C433 C436C437 3 FL401 R414 R415 R420 R426R463 C434C435 CR411 Q416R419 R460 R461R462 SH402 U410C328 C359C390 C3763D3761R373 R374R375 R377 R3781 4 5 8 U303 VR442 C3212 R3214 R3215 R3761 U3201 C337C358 C383 C3213C3215 CR501L505 R370 R371...
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Circuit Board/Schematic Diagrams and Parts List79FMR-2045A-2December 26, 2003 Figure 8-3. VHF Controls And Switches Schematic Diagram VOL MECH_SWB+ Vdda 6.8VVR501 HIGH TAB1 6 TAB2 7 2 mgc_comps 4 1LOW5 3S502 C502 0.47uF C505100pF UNSWB+ 1000pF1000pFC535 100pFC503 CR501VR439 10V2 124V F501 BATT_CODE SB1 EMER LI_ION VR506 6.8VL505 390nHB501 DATA NEG POS B503 B504.01uFC520 .01uFC521 1 2SWITCHPB505 VR440 NU6.8V PB501 1 2 SWITCH PB504 1 2 SWITCH NU 6.8V VR444 PTT PB502 1 2 SWITCH VR441 NU6.8VC522 .01uF SB2...
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80Circuit Board/Schematic Diagrams and Parts ListDecember 26, 2003FMR-2045A-2 Figure 8-4. VHF Receiver Front-End Schematic Diagram G UNSWB_PLUS_1_RX C3336 10uF UNSWB+UNSWB_PLUS_2_RX G L3301 12nH RX_INC3302 150pF RX_IN_1_FE 5.6pF C3301C3303 15pF D3301CR3303 L3303 12nHC3304 150pF 33KR3307 NU C3305 NU C3326 470pFC3338 470pF R3304 100KR3308 1.5K R3311 NU 7.5K R3309 5.1 R3312 0.1uF C3306 Q330239 R3313 L3304 470nH R3315 330 C3308 330pF 100pF C3307 2.7K R3310 16pF C3312 150pF C3311 R3314 27 D3302 NU...