Kenwood NXR-700H Service Manual

NXR-700H142-2. Transmitter reference 19.2MHz PLL circuitThe transmitter reference 19.2MHz PLL circuit producesa reference frequency signal for the transmitter modulation19.2MHz PLL circuit, the Receiver unit (X55-309) ReceiverDDS circuit and the Control Unit (X53-414) DSP IC.This circuit consists of Q401, Q402, Q412, Q415, Q416,Q417, X401, IC404, and IC407.The 5.99MHz or 10MHz signal produced by the internal/external reference circuit is amplified by IC407 and suppliedto the PLL IC (IC404) reference signal pin.The VCXO (X401) signal enters buffer amp Q417 and isamplified by Q415. The higher harmonic wave is attenuatedby LPF and returns to IC404. Its phase is compared withthat of the reference frequency 10kHz.The phase difference signal produced by the comparingphase is converted to a DC voltage by a lag-lead type loopfilter. This DC voltage is input to the X401 control voltageterminal for controlling the VCXO oscillating frequency.The DC voltage passes through the IC401 operational am-plifier, and is output as a voltage signal (CVT-REF) for moni-toring the reference 19.2MHz PLL circuit lock voltage.The stabilized 19.2MHz reference oscillating signal en-ters the Q417 buffer amplifier and is amplified by Q412 andQ416. The higher harmonic wave is attenuated by LPF, fedto IC302 and used as the reference frequency signal for thetransmitter modulation 19.2MHz PLL circuit.The 19.2MHz reference oscillating signal is also used asthe reference signal for the receiver unit (X55-309) and con-trol unit (X53-414).It enters the Q417 buffer amplifier for the receiver unit(X55-309) and is amplified by Q401. The higher harmonicwave is attenuated by LPF and is output from CN406.It enters the Q417 buffer amplifier for the control unit(X53-414) and is amplified by Q402. The higher harmonicwave is attenuated by LPF and is output from CN405.Q415Internal/ExternalRef circuit1/R1/NPDFref.=19.2MHzR=1920Fpd=10kHz8V #2Q417X4018V #2IC4075V #3Q4165V #1Q4015V #2Q4025V #2Q4125V #18V #25V #35V #319.2MHz 19.2MHzIC401OP-AMP2865.99MHzor10MHzIC404PLL ICCVT-REFTX Mod19.2MHzPLL circuitRX unitControlunitCN40619.2MHzCN40519.2MHzFig. 2 Transmitter reference 19.2MHz PLL circuit / 图 2 发射机基准 19.2MHz PLL 电路CIRCUIT DESCRIPTION / 电路说明2-2. 发射机基准 19.2MHz PLL 电路发射机基准 19.2M H z P L L 电路产生发射机调制 19.2M H zPLL 电路、接收机单元 (X55-309) 接收机 DDS 电路和控制单元(X53-414)DSP IC 的基准频率信号。该电路由 Q401、Q402、Q412、Q415、Q416、Q417、X401、IC404 和 IC407 组成。内部 / 外部基准电路产生的 5.99MHz 或 10MHz 信号由 IC407放大并提供给 PLL IC(IC404) 基准信号针脚。V C X O ( X401) 信号进入缓冲放大器 Q417，由 Q415 放大。较高的谐波由 LPF 衰减并返回 IC404。其相位与基准频率 10kHz的相位进行对比。通过相位对比产生的相位差信号由一个滞后超前式环路滤波器转换为 DC 电压。该 DC 电压被输入用于控制 VCXO 振荡频率的 X401 控制电压端子。DC 电压通过 IC401 运算放大器，输出为电压信号 (CVT-REF)，用于监测基准 19.2MHz PLL 电路锁定电压。经过稳定的 19.2M H z 基准振荡信号进入 Q417 缓冲放大器，由 Q412 和 Q416 放大。较高的谐波由 L P F 衰减，送入 I C302，并用作发射机调制 19.2MHz PLL 电路的基准频率信号。19.2M H z 基准振荡信号还用作接收机单元 ( X55-309) 和控制单元 (X53-414) 的基准信号。它进入接收机单元 (X55-309) 的 Q417 缓冲放大器，由 Q401放大。较高的谐波由 LPF 衰减，从 CN406 输出。它进入控制单元 ( X53-414) 的 Q417 缓冲放大器，由 Q402放大。较高的谐波由 LPF 衰减，从 CN405 输出。