Kenwood NX-820 Service Manual

Also see for NEXEDGE NX-820: Instruction manual Technical details Instruction manual Instruction manual Quick start guide

Contents

NX-82027CIRCUIT DESCRIPTION / 电路说明8. Signaling Circuit8-1. Encode (QT/DQT/DTMF/2-tone/MSK)Each signaling data signal of the QT, DQT, DTMF, 2-toneand MSK is generated by the DSP circuit, superposed on amodulation signal and output from the ASIC (IC507). Eachdeviation of the TX QT, DQT, DTMF, 2-tone and MSK tonesare adjusted by changing the output level of the DSP (IC502)and the resulting signal is routed to the VCO and PLL.8-2. Decode (QT/DQT/DTMF/2-tone/MSK)The audio signal is removed from the FM detection signalsent to the DSP circuit and the resulting signal is decodedby the DSP.9. Compander CircuitThe term “compander” means compressor and expander.The compander reduces noise by utilizing a compressor andan expander. The DSP (IC502) performs this operation. TheCompander can be turned on or off using the FPU.8. 信令电路8-1. 编码 (QT/DQT/DTMF/2 音 /MSK)DSP 电路生成 QT、DQT、DTMF、2 音和 MSK 的各信令信号，这些信号被叠加到调制信号上并从 ASIC (IC507) 输出。TXQT、DQT、DTMF、2 音和 MSK 音各自的频偏通过改变 DSP (IC502)的输出电平进行调整，产生的信号被送至 VCO 和 PLL。8-2. 解码 (QT/DQT/DTMF/2 音 /MSK)音频信号从发送到 DSP 电路的 FM 检测信号中提取，产生的信号由 DSP 解码。9. 压扩器电路“Compander”一词表示压缩器和扩展器。压扩器利用压缩器和扩展器减低噪音。DSP (IC502) 用以执行此操作。可用FPU 开启或关闭压扩器。