Icom ID-51E User Manual

Also see for ID-51A: Manual Manual Basic instructions Brochure & specs Basic instructions

Contents

Icom ID-51E User Manual Manual pdf 16 page image

4 - 74-3 FREQUENCY SYNTHESIZER CIRCUIT(MAIN UNIT)VCOsThe ID-51A/E has total of four VCOs; two VCOs for band Aand another two for band B.• Band AVHF VCO (VCO1 UNIT)The VHF VCO (Q311, D304–D306) generates both 1st LOsignal (for receiving a VHF signal on band A) and the VHFTX signal. The output of buffer (Q200) is amplifi ed by the LOAMP (Q201), and then used as the VHF TX/RX LO signal.While receiving, the LO signal is applied to the 1st IF mixer(Q820) for receiving a signal on the VHF band, through theRF SW (D821).While transmitting, the LO signal is applied to the TX AMPcircuits, through the LO SW (D14).UHF VCO (VCO1 UNIT)The UHF VCO (Q27, D10–D12) generates both 1st LO signal(for receiving a UHF signal on band A) and the UHF TX sig-nal. The output of buffer (Q200) is amplifi ed by the LO AMP(Q201), and then used as the UHF TX/RX LO signal.While receiving, the LO signal is applied to the 1st IF mixer(Q801) for receiving a signal on the UHF band, through theRF SW (D802).While transmitting, the LO signal is applied to the TX AMPcircuits, through the LO SW (D14).• Band BVHF VCO (VCO2 UNIT)The VHF VCO (Q311, D304–D306) generates the 1st LOsignal (for receiving a VHF signal on band B). The output ofbuffer (Q200) is amplifi ed by the LO AMP (Q201), and thenused as the 1st LO signal.While receiving, the LO signal is applied to the 1st IF mixer(MAIN UNIT: Q830) for receiving a signal on the VHF band,through the RF SW (MAIN UNIT: D831).UHF VCO (VCO1 UNIT)The UHF VCO (Q27, D10–D12) generates 1st LO signal(for receiving a UHF signal on band B). The output of buffer(Q200) is amplified by the LO AMP (Q201), and then used asthe UHF TX/RX LO signal.While receiving, the LO signal is applied to the 1st IF mixer(MAIN UNIT: Q811) for receiving a signal on the UHF band,through the RF SW (MAIN UNIT: D812).PLL• Band AA portion of VHF and UHF VCOs output signal is amplifi edby two buffers (VCO1 UNIT: Q200 and Q202) and passedthrough the LPF (VCO1 UNIT: L202, C209 to C211), andthen fed back to the PLL IC (IC6, pin 8).The PLL IC (IC6) phase-compares the output of referencefrequency oscillator (TCXO; X1) and VCO, and the phase dif-ference is output as the charge pump current. The current ispassed though the loop fi lter (R67, R71, R90, R93, C91, C92,C96 and C102) to be converted into the lock voltage, whichcontrols the oscillating frequency of VCO.When the oscillation frequency drifts, its phase changes fromthat of the reference frequency, causing a lock voltage changeto compensate for the drift in the VCO oscillating frequency.Band BA portion of VHF and UHF VCOs output signal is amplifi edby two buffers (VCO2 UNIT: Q200 and Q202) and passedthrough the LPF (VCO2 UNIT: L202, C209 to C211), andthen fed back to the PLL IC (IC6, pin 8).The PLL IC (IC6) phase-compares the output of referencefrequency oscillator (TCXO; X1) and VCO, and the phase dif-ference is output as the charge pump current. The currentis passed though the loop fi lter (R452, R454, R455, R457,C455, C457 to C460) to be converted into the lock voltage,which controls the oscillating frequency of VCO.When the oscillation frequency drifts, its phase changes fromthat of the reference frequency, causing a lock voltage changeto compensate for the drift in the VCO oscillating frequency.FINX1Q202Q311,D304,D305,D30615.3MHzIC6Q201Q200VCO1 UNITVCO2 UNITLOSWD14A_LOTX AMP circuit. ->B_LOQ811Q830D812,D831Q801Q820VHF 1st LOUHF 1st LOVHF 1st LOUHF 1st LOREFMODQ27,D10,D11,D12VHFUHFQ202Q200Q27,D10,D11,D12Q201UHFVHFFINIC450Q311,D304,D305,D306D802,D821A_LOOUTLPFFILLOOPVCO BUFFPLLICLOAMPRFSWRFSWVCOBUFFPLLICLPFVCOVCO BUFFAMPLOAMPFILLOOPVCOMOD• FREQUENCY SYNTHESIZER CIRCUIT