Kenwood NXR-710 Service Manual

Also see for NEXEDGE NXR-710: Instruction manual Instruction manual Instruction manual Instruction manual Instruction manual

NXR-71011volume control circuit. The 2nd electronic volume controlcircuit adjusts the modulating signal and is fed to IC606.IC603 is an inverting amplifier for inverting the amplifi-cation of the modulating signal. The output of IC603 andthe charge pump output of IC602 (Transmitter modulation16.8MHz PLL IC) are synthesized by IC604 and is fed toVCXO (X600).IC606 is a non-inverting amplifier. The output of the 2ndelectronic volume control circuit is amplified by IC606 and isfed to the transmitter main PLL circuit.AMPIC604AMPIC606AMPIC603VREFIC605EVOLIC804X58-5080-10X600MBMODCN800MOOSC16.8MHzTX VCO/PLLFig. 5 Modulation level adjustment circuit2-5. Front-end circuitThe front-end circuit consists of LPF, L111, L112, L114,and L115 coils, former BPF tuning Variable CapacitanceDiodes (D105, D106, D107 and D108), RF amplifier Q101(LNA), L100, L101, L103, and L104 coils, and latter BPFtuning Variable Capacitance Diodes (D100, D101, D103 andD104). The BPF covers frequency ranges 136 to 174MHz.The LPF, former and latter BPF attenuate the unwantedsignals receiving from RX antenna (CN101) and only the de-sired signals transmit to the 1st-mixer.LNA AMPQ101BufferIC100BufferIC101136~174MHzBPFEVOLIC804BPF LPF RX ANTCN101136~174MHzFig. 6 Front-end circuit2-6. 1st-Mixer circuitThe signal passing the front-end circuit is heterodynedwith the first local oscillator signal from the PLL frequencysynthesizer circuit at the first mixer (IC300) to become a58.05 MHz first intermediate frequency (IF) signal.1st Local194.05~232.05MHzMixerIC300136~174MHzIF158.05MHzFig. 7 1st-Mixer circuit2-7. IF circuitThe first IF signal is amplifi ed by the IF Post Amp (Q301)and passed through a four-pole monolithic crystal filter(XF300) to reject adjacent channel signals. The filtered firstIF signal is amplified by the IF AGC amplifier (Q300) andthen applied to the IF system IC (IC403). The IF system ICSW450kHzRSSICN802AGC58.05MHzIF ICIC403IC405SWIC406 CF402CF403CF401SWIC408SWIC407CF400RSSIIF2AGCIF12nd Lo57.6MHzIF AMPIC404IF AMPIC400MCFXF300IF AGC AMPQ300POST AMPQ301Diff AMPIC401(B/2)AMPIC409(A/2,B/2)BufferIC401(A/2)BufferIC402Fig. 8 IF circuitCIRCUIT DESCRIPTION