Icom IC-R9500 Service Manual

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Icom IC-R9500 Service Manual Manual pdf 11 page image

3 - 3-VIDEO AM-DEMODULATION- (except for USA version)The 2nd IF signal divide at the splitter is amplified and filtered, then converted into the 3rd IF (video IF) signal at 3rd mixer (IC2201).The converted video IF signal is amplified, then passed through the video IF filters. The filtered video IF signal is applied to thevideo demodulation IC and AM-demodulated.The demodulated video signals are passed through Band Eliminate Filter (BEF; as the trap) to remove unwanted beatcomponents. The fi ltered signal is buffer-amplifi ed and output from the video jack on the CONNECT-B UNIT.3-2 FREQUENCY SYNTHESIZEROSC UNITThe OSC UNIT supplies very high stability 10.000000 MHzstandard frequency signal generated by the OCXO (OvenControlled X’tal Oscillator). The oscillated referencefrequency signal is buffer-amplified and amplified and filteredto remove harmonic components at the LPF. The filteredreference frequency signal is applied to the PLL UNIT viathe buffer.The reference frequency signal is also available from theexternal reference frequency source (10.000000 MHz)via [REF I/O] (CONNECT-B UNIT; J201). The referencefrequency signal from the CONNECT-B UNIT is passedthrough the attenuators, BPF and switches, then buffer-amplifi ed before being applied to the PLL UNIT.BPFATTIFAMPQ1 IC101IC2201SPM5001IC201/IC203 IC202/IC204BUFFQ2ATT ATTIFAMPQ2101BPFBPFBUFFQ301IFAMPQ2181BPFBPFVIDEO48MHzAGCTPSCC4.5MBTPSCC5.5MBTPSCC6.0MBTR4_5MTR5_5MTR6_0M-10dBmTR4_5MTR5_5MTR6_0MTR6_5MTR6_5M TPSCC6.5MBSWFILTER FILTERSWTRAPTRAPTRAPTRAPDETECT2nd IF signalfrom the RF-A UNIT2nd LO signalfrom the PLL UNITComposit video signalto the J601 (CONNECT-B UNIT)• VIDEO AM-DEMODULATION CIRCUITBPFATTBUFFQ70LPF BUFF2SC4081Q21AMPQ61/Q62AMPQ22X1AMPQ42LPFEXT-REF OUT(10.000000MHz OCXO)EXT-REF IN10MHz10MHz10MHz• OSC CIRCUITSFrom [REF I/O] (CONNECT-B; J201)10.000.000 MHzStandard signalFILLOOPIC1001Q1201BUFFQ1102ATTATTAMPIC1351BUFFQ1202Q1101ATTBUFFQ1302ATTQ1301AMPIC1300PLLICIC1000Ref 500kHz514.35~639.35MHz317.8~391.3MHz389.35~521.3MHz10.5MHzLH1VLH2VLH3VDATACKPST1P6dBHYB317.8~639.35MHz317.8~639.35MHzVCO-CVCO-BVCO-ATo FIL1 BOARD1st LO signalsto RF-A UNITVCO1 BOARD• VCO-A, VCO-B, VCO-C LOOPPLL UNITPLL UNIT supplies the LO (Local Oscillator) signals(1st, 2nd, 3rd and 4th), still more the clock signals forDSP circuits. To obtain physical strength for the VCO1,VCO2, DOUBLER, FIL1 and FIL2 BOARDs, these circuitsare shielded and isolated perfectly, by being patternedseparately on different P.C. boards.VCO1 BOARDVCO1 BOARD has tree VCOs ;VCO-A, VCO-B and VCO-C.VCO-A (Q1301), as an example, is a colpitts-typed oscillatorcircuit, and its output signal is buffered by Q1302 and outputvia diode switch. Q1303 controls the power supply for theVCO, and the voltage of LH3V line adjusts the oscillationlevel for suitable LO signal level.The buffer-amplified VCO output signals are divided by thedivider, and applied to the LO amplifier via attenuator (asa pad). The amplified LO signals are applied to the RF-AUNIT or FIL1 BOARD as the 1st LO signals, via filters andamplifi ers.The VCO-A is mounted on the nearest to VCO1 board toreduce the signal loss. The resonators are employed striplines which had been used with SMD electric parts. Theoscillating frequency ranges are divide into three for wideoscillation frequency coverage.