Kenwood NXR-700H Service Manual

NXR-700H24D9SWD13SWQ25SWQ32SWQ31SWQ26SWL46,52XF1L74,90XF3Q19 Q28Analog Wide8WR8WRD10SWD14SWL47,53XF2L75,91XF4Q20 Q29Analog NarrowNXDN NarrowNXDN Very-Narrow8NR8NR+8VIF_SW4-4. Demodulator circuitsThe desired signal that passed through the 1st-IF circuitspasses through the distributor consisting of LC parts and isfed to the IF system IC_IC12, IC13. The signal in Analog_Wide or Analog_Narrow mode is mixed with the secondlocal oscillator hetero signal by the mixer in IC12. 450kHz isproduced as the 2nd Intermediate Frequency (IF2).It passes through D15, CF2, D16, D19, CF5 and D20 pathif the modulation mode is Analog_Wide. It passes throughD15, CF3, D16 and D19, CF7 and D20 path if the modulationmode is Analog_Narrow. The base band signal FM-detectedby the quadrature detection circuit consisting of L128, Q57,and Q58 and is amplified to a signal level of approximately100mVrms by IC20 and is then transmitted to the controlunit (X53-413) from CN42 (pin12).The signal in NXDN_Narrow or NXDN_Very-Narrow modeis mixed with the second local oscillator hetero signal by themixer in IC13. 450kHz is produced as the 2nd IntermediateFrequency (IF2). Here, irrespective of modulation modes, itpasses through the CF4 and CF6 path. It is transmitted asthe base band signal via IC14 to the CN43 control unit, X53-414.CF2, CF3, CF4, CF5, CF6 and CF7 are hexode CeramicFilters. They are BPF for removing spurious noise occurringclose to the desired signal.4-5. Squelch circuitThe desired noise of the noise component output from IFsystem IC_IC12 (pin18) is extracted by the BPF. After pass-ing through Q40, it is DC-detected as the squelch voltage byD17, D18 and input to ADC_IC30 (pin11).The MPU mounted in the control unit (X53-413) comparesit with a predetermined reference voltage and turns the Au-dio signal on and off. The strength of the receiver signal in-put from CN5 is output as the RSSI voltage from IF systemIC_IC12 (pin21), and is input to_IC30 (ADC) pin12 via IC29A/2.CIRCUIT DESCRIPTION / 电路说明Fig. 18 1st-IF circuits / 图 18 第 1 IF 电路4-4. 解调器电路通过第 1 IF 电路的所需信号通过由 LC 部分组成的分配器，被送入 IF 系统 IC_IC12、IC13。模拟宽或模拟窄模式的信号由 I C12 中的混频器与第二本地振荡器外差信号混合。产生450kHz，作为第 2 中频 (IF2)。如果调制模式为模拟宽，则它通过 D15、C F2、D16、D19、C F5 和 D20 的路径。如果调制模式为模拟窄，则它通过 D15、C F3、D16 和 D19、C F7 和 D20 的路径。由 L128、Q57 和 Q58组成的积分检测电路 F M 检测的基带信号被 I C20 放大到约100m V r m s 的信号电平，然后从 C N42( 针脚 12) 传送到控制单元 (X53-413)。NXDN 窄或 NXDN 超窄模式的信号由 IC13 中的混频器与第二本地振荡器外差信号混合。产生 450kHz，作为第 2 中频 (IF2)。在此处，不论调制模式如何，它都通过 C F4 和 C F6 路径。它被作为基带信号经 IC14 发送到 CN43 控制单元、X53-414。C F2、C F3、C F4、C F5、C F6 和 C F7 是六极管陶瓷滤波器。它们是用于消除所需信号附近发生的寄生噪声的 BPF。4-5. 静噪电路从 I F 系统 I C _ I C12( 针脚 18) 输出的噪音分量的所需噪音由 BPF 提取。通过 Q40 后，D17、D18 对其进行 DC 检波作为静噪电压，并输入到 ADC_IC30( 针脚 11)。装于控制单元 ( X53-413) 上的 M P U 将其与预定的基准电压相比较，并打开和关闭音频信号。CN5 输出的接收机信号的强度作为 RSSI 电压从 IF 系统 IC_IC12( 针脚 21) 输出，经 IC29A/2 输入到 _IC30(ADC) 针脚 12。