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SEC-900型收录机是四波段双通道六扬声器立体声系统,它的整机电路原理图如图1所示。一、收音部分本机收音部分主要采用集成度较高的 TDA1220型集成块,它被用作调幅振荡、混频、中放、检波以及调频中放和鉴频,集成电路 LA3361被用作立体声解调。调频头由 Q_1(高放)和 Q_2(变频)组成。L_1C_5谐振回路与耦合电容器 C_1、C_6、L_2共同构成不调谐的天线输入回路。输入回路具有 Q 值低、频带宽的特性,并以98MHz 固定频率谐振,它的作用是使天线与高频放大器实现匹配和耦合。
SEC-900 type recorder is a four-band dual-channel six-speaker stereo system, its circuit diagram of the whole machine shown in Figure 1. First, the radio part of the main radio part of the main use of highly integrated TDA1220-type integrated block, which is used for amplitude modulation oscillation, mixing, release, detection and FM and Fangzhao frequency, integrated circuit LA3361 was used as a stereo solution Tune The FM tuner consists of Q_1 (High Amplifier) and Q_2 (Inverter). The L_1C_5 resonant circuit and the coupling capacitors C_1, C_6 and L_2 together form an un-tuned antenna input loop. The input circuit has the characteristics of low Q, wide bandwidth and resonates at a fixed frequency of 98 MHz. Its function is to match and couple the antenna with the high frequency amplifier.