Icom IC-E7 Service Manual

Also see for IC-E7: Instruction manual Service manual Instruction manual

Contents

SECTION 4 CIRCUIT DESCRIPTION4-1 RECEIVE CIRCUITS4-1-1RF CIRCUITS (MAIN UNIT)This transceiver has 4 RF circuits to provide wide receivingrange. The received signals from the antenna connector(CHASSIS; J1) are applied to each RF circuits for the frequencycoverage, and amplified within the frequency coverage.• While receiving 0.495–76 MHzThe 0.495–76 MHz band signals are passed through thethree low-pass filters (LPF; L32, L34, L39, L42, C284, C290,C294, C307, C314), then applied to the RF amplifier (Q38)via the band switches (D30, D43) and LPF or BPF.The 0.495–30 MHz band signals are passed through theLPF (L20, C241, C242, C247), the 30–76 MHz signals arepassed through the Bandpass Filter (BPF; D39, L21, L24,C238, C256) before being applied to the RF amplifier (Q38).The amplified signals are applied to the 1st mixer (IC16, pin1) via the band switch (D16).- 0.495–76 MHz -• While receiving 76–300 MHzThe 76–300 MHz band signals are passed through two LPFs(L39, L42, C307, C314) and a couple of High-pass Filter (HPF;L33, C287, C293) and LPF (L29, L31, C266, C269, C276,C283, C514, C516), then applied to the RF amplifier (Q42) viathe antenna switching circuit (D35, D38) and the LPF (D53,L44, C295, C303).The amplified signals are then applied to the 1st mixer (IC16, pin1) via the BPF (D27, D28, D31, D36, L10, L11, L22, L23, C208,C210, C216, C228, C233, C243) and band switch (D21).- 76–300 MHz -4 - 1ST)&SIGNALTOTHE&-)&)#)# PIN -(Z7&-$ &)&)1$-(Z!-&-2ECEIVEDSIGNALSFROMTHE2&CIRCUITSSIGNALSFROMTHE6#/SST)&AMP "0&"0&STMIXER)#to the1st mixer(IC16, pin 1)0.495–30 MHzD39D16D30Q38 D43 D4430–76 MHzfrom theantennaRFampLPFATTBPFLPFLPF3 LPF’sto the1st mixer(IC16, pin 1)D21D53D27, D28,D31, D36 Q42from theantennaBPF LPFLPFLPF HPFLPFRFamp2 LPF’sD35, D38ANTSW• While receiving 300–500 MHzThe 300–500 MHz band signals are passed through the LPF(L42, C314) and a couple of HPF (L38, C302, C306) andLPF (D41, D45, L26, L30, C255, C257, C262, C275, C282,C289, C515), then applied to the RF amplifier (Q43) via theantenna switching circuit (D34, D37) and the BPF (D55, L36,L106, C304, C522, C523).The amplified signals are then applied to the 1st mixer(IC16, pin 1) via the BPF (D26, D32, L13, L25, C204, C215,C222, C236, C244, C520, C521) and band switch (D22).- 300–500 MHz -to the1st mixer(IC16, pin 1)D55 D41, D45D26, D32D22 Q43LPFBPFBPF HPFLPF from theantennaRFampD34, D37ANTSW• While receiving 500–999 MHzThe 500–999 MHz band signals are passed through the HPF(L41, C311, C313) and band switch (D54), then applied tothe RF amplifier (Q45) via the attenuator (D46). The amplifiedRF signals are applied to another RF amplifier (Q39) via theBPF (D33, D40, L15, L27, L28, C229, C237, C245, C252,C261). The amplified RF signals are then applied to the 1stmixer (IC16, pin 1) via the band switch (D23).- 500–999 MHz -to the1st mixer(IC16, pin 1)D23 Q39 Q45 D54D46ATT from theantennaHPFBPFRFamp RFampD33, D404-1-2 1ST IF CIRCUITS (MAIN UNIT)The 1st IF circuits contain the 1st mixer, 1st IF amplifierand the 1st IF filter. The 1st IF mixer converts the receivedsignals into a fixed frequency of the 1st IntermediateFrequency (IF) signal. The converted 1st IF signal is filteredat the 1st IF filters, then amplified at the 1st IF amplifier.The received signals from the RF circuits are applied to the1st IF mixer (IC16, pin 1), and converted into the 46.35 MHz(AM/FM)/14.85 MHz (WFM) 1st IF signal by being mixedwith 1st Local Oscillator (LO) signals from the VCOs (VCOBOARD).While receiving 0.5–76 MHz band signals, the 1st LO signalsare generated at 50 MHz VCO (VCO BOARD; Q10, Q13,D7, D8), and for receiving 76–280 MHz band signals, the 1stLO signals are generated at 144 MHz VCO (VCO BOARD;Q9, Q12, D6).While receiving 280–999 MHz band signals, the 1st LOsignals are generated at 430 MHz VCO (VCO BOARD; Q8,Q11, D5). If the receiving frequency is 500 MHz and above,the VCO output signal is doubled at the doubler circuit (Q18)before being to applied to the 1st mixer (IC16, pin 3).The converted IF signal is passed through the 1st IF filterFI3 (AM/FM mode) or FI2 (WFM mode) to filter out theunwanted signal, then applied to the 1st IF amplifier (Q9).The amplified 1st IF signal is then applied to the FM IF IC(IC15, pin 16).• 1st IF CIRCUIT