Icom IC-F1000 Service Manual

Also see for IC-F1000 series: Instructions Operating guide Instructions Instructions Instructions

Contents

Icom IC-F1000 Service Manual Manual pdf 10 page image

4-3• TX AF CIRCUIT• MODULATION CIRCUITTo the modulation circuitVOL1R133MC1LPFIC11J1AMPLIMITAMP MICGAINIC2MODIC10 AFSWEMPH COMPSPLT HPFIC2IC4TX/RXSWD16Q27,D11,D12,D33FREQUENCYMODULATIOND13BUFFQ31BUFFQ30TX VCOFrom the TX AF circuitsTo the TX AMP circuits4-2 TRANSMIT CIRCUITSTX AF CIRCUITThe audio signal from the internal or external microphone(MIC signal) is passed through the MIC gain SW (IC2) andapplied to the baseband IC (IC4).The processed AF signal is passed through the AFSW (IC2) and LPF (IC11), and then applied to the D/Aconverter (IC10), which adjusts its level (=deviation). Thelevel-adjusted MIC signal is applied to the TX VCO as themodulation signal.MODULATION CIRCUITThe modulation signal from the TX AF circuits is appliedto D13 of the TX VCO (Q27, D11 to D13 and D33). Thefrequency-modulated signal from is amplified by two buffers(Q30 and Q31), and then applied to the TX AMP circuit,through the TX/RX SW (D16).• TX AMPLIFIERS AND APC CIRCUITLPFPWRDETD22,D23ANTSWD19,D27PWRAM PQ38APCAMPIC17DRIVEAM PQ36ANTFrom theTX VCOTo the RX circuitsAMPPREQ34TX AMP CIRCUITThe buffer amplified signal from the TX/RX SW (D16)is sequentially amplified by the pre-AMP (Q34), driveAMP (Q36) and power AMP (Q38). The power amplified TXsignal is passed through the antenna SW (D19) and LPF(L29 to L31, C333, C347 to C350, C352 and C403), andthen applied to the antenna.APC CIRCUITSAt the TX output power detector, the RF signal at the LPF(L26, C303, C330, C353 and C355) is rectified by thediodes (D22 and D23), and it is used as the TX power sens-ing voltage.The voltage is applied to the APC AMP (IC17), and theoutput voltage controls the bias voltages of the drive AMP(Q36) and power AMP (Q38) to keep the TX output powerconstant.• FREQUENCY SYNTHESIZER CIRCUITS4-4 VOLTAGE BLOCK DIAGRAM1st IF mixerTX/RXSWD16D17Q25D9,D10Q27D11,D12FILRIPPLEQ23VCOSWQ29FILLOOPPLLIC IC15X3Q26Q37BPFBUFFQ31BUFFQ30BUFFQ32X3CR-794TCXOLVADJD11LVADJD10BUFFIC7IF ICR5VRX VCOTX VCOIC16REFBAL15.3MHz45.9MHzLVLVA×2To the TX AMPsHPF** LPF*To the TX circuitsTo the RX circuitsTo both RX and TX circuitsTo both RX and TX circuitsTo the logical circuitsF11 2T5REGQ17REG+5VIC20REGS5Q15BATTERY_1BT1S5REGR5Q16CPU5REGIC6S5CVCCR5C+5VT5CS5VR5VPWONVCCCPU5T5V4-3 FREQUENCY SYNTHESIZER CIRCUITSThe RX VCO is composed of Q25, D9, D10 and D32. Theoutput signal is amplified by two buffers (Q31 and Q31) andapplied to the 1st IF mixer (Q37), through the LO SW (D17)and LO filter (LPF*: L41, C296 and C441, or HPF**: L21,L42 and C293).The TX VCO is composed of Q27, D11 to D13 and D33.The output signal is amplified by two buffers (Q30 and Q31)and applied to the pre-AMP (Q34), through the LO SW (D16).A portion of oscillated VCO output signal from each VCO isfed back to the PLL IC (IC15), through the buffer (Q32) andLPF (L11, C210 and C231).The applied VCO output signal is divided and phase-compared with a 15.3 MHz reference frequency signal fromthe TCXO (X3), which is also divided. The resulting signalis output from the PLL IC (IC15), and DC-converted by theloop filter, and then applied to the VCO as the lock voltage.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.*:For [EUR] and [UK] versions.**:For except [EUR] and [UK] versions.