Icom IC-F5012 Service Manual

Also see for IC-F5011: Price list Instructions

Contents

5 - 45-3 FREQUENCY SYNTHSIZER CIRCUITSVCOs (MAIN-A UNIT)The TX VCO which generates the TX signal is composedby Q13, D16, D31, L25, L38, etc., and the frequencymodulation is carried out by applying modulation signals toD18.The RX VCO which generates the 1st LO signals iscomposed by Q14, D33, D34, L26, L39, etc.These two VCOs are switched by the VCO SW (Q15, 16)using “RXC” signal.The output signal from each VCO is amplified by the bufferAMP (Q11) and LO AMP (Q10), and then applied to the TXor RX circuits.A portion of generated signals is applied to the PLL IC (IC4)via buffer AMP (Q12).• FREQUENCY SYNTHESIZER CIRCUITS5-4 VOLTAGE DIAGRAMVoltage from the power supply is routed to the whole of the transceiver via regulators and switches.PLL (MAIN-A UNIT)The applied VCO output is divided according to the serialdata including divide ratio from the CPU, at the prescalerand programmable divider. In the same way, the referencefrequency signal from the reference frequency signaloscillator is applied to the PLL IC and divide so that theseare the same frequency.The frequency-matched signal is applied to the phasecomparator and phase-compared. The resulted phasedifference is detected as a phase-type signal, and level-adjusted at the charge pump then output. The output pulsetype signal is passed through the loop filter to be convertedinto the DC voltage (=Lock Voltage).Applying the lock voltage to the variable capacitors(VD) which composes a part of the resonator of VCO,the capacitance of VDs changes corresponding to theapplied lock voltage. This causes the change of resonationfrequency that determines the VCO oscillating frequency tokeep the VCO frequency constant.When the oscillation frequency drifts, its phase changesfrom that of the reference frequency, causing a lock voltagechange to compensate for the drift in the VCO oscillatingfrequency.LPFREFX2LOSWD14,D15Q14,D33,34Q13,D16,31FILRIPPLEQ17VCOSWQ15,16FILLOOPPLLICIC4X3Q34FMMODD18BPFBUFFQ10BUFFQ11LPFIC19AMPX2Q12BPFD54,55TLVADJD53RLVADJD52IF IC8VRXCRX VCOTX VCOIC1REF 15.3MHzClock,Data,Strobe45.9MHz182.35 MHz-220.35 MHz136/146 MHz-1740 MHzTXCT8VRLVATLVALVLVSWPOWERQ23,Q24+55VREGQ27,Q28+8REGIC9T8REGQ25,Q29,D23W2Power supply cableREGCPU5IC10Q26,Q30R8REGDrive AMP(Q9), APC AMP(IC2), etc.IF IC (IC1), PLL IC(IC4), etc.RF AMP(Q2), 1st IF AMP(Q4), 1st mixer(Q3), etc.External output(from J6)VCOs, FRONT UNITT8VR8V8VVCCTMUTRXCPWONHVCPU5CPU5VCC8V8V8VHPA module(IC3) HV