Kenwood TK-3118 Service Manual

Also see for TK-3118: Service manual

14TK-3118TK-260 :K, K2Fig. 4 PLL circuit / 图4 锁相环电路3) UNLOCK DETECTORIf a pulse signal appears at the LD pin of IC1, an unlockcondition occurs, and the DC voltage obtained from D2, R4,and C12 causes the voltage applied to the UL pin of themicroprocessor to go low. When the microprocessor detectsthis condition, the transmitter is disabled, ignoring the push-to-talk switch input signal. ( See Fig.5)4. Transmitter1) Transmit audioThe modulation signal from the microphone is amplified byIC308 (A/4), passes through a preemphasis circuit, andamplified by the other IC308 (B/4) to perform IDC operation.The signal then passes through a low-pass filter (splatter fiIter)IC308 (C/4 and D/4) and cuts 3kHz and higher frequencies.The resulting signal goes to the VCO through the VCOmodulation terminal for direct FM modulation. (See Fig. 6)2) QT/DQT encoderA necessary signal for QT/DQT encoding is generated byIC300 and FM-modulated to the PLL reference signal. Sincethe reference OSC does not modulate the loop characteristicfrequency or higher, modulation is performed at the VCO sideby adjusting the balance. (See Fig. 6)Fig. 5 Unlock detector circuit / 图5 失锁检测器电路IC1LDPLL ICD2C12R45CIC300ULMPUPLL DATA12.8MHzREF OSCI/MI/NPLL IC IC1PHASECOMPARATORCHARGEPUMPLPF5kHz/6.25kHzD6, 9D7, 11Q5TX VCOQ4RX VCOQ7BUFF AMPQ3RF AMPQ8, 9T/R SW5kHz/6.25kHz2) VCOThe operating frequency is generated by Q5 in transmitmode and Q4 in receive mode. The oscillator frequency iscontrolled by applying the VCO control voltage, obtained fromthe phase comparator, to the varactor diodes (D6 and D9 intransmit mode and D7 and D11 in receive mode). The T/R pinis set high in receive mode causing Q8 and Q9 to turn Q5 off,and turn Q4 on . The T/R pin is set low in transmit mode. Theoutputs from Q4 and Q5 are amplified by Q7 and sent to thebuffer amplifiers.CIRCUIT DESCRIPTION / 电路说明2) 压控振荡器在发射模式中通过Q 5 产生操作频率，在接收模式中通过Q 4产生操作频率。通过相位比较器到变容二极管 ( 在发射模式中为D6和D9，在接收模式中为D7和D11) 采用压控振荡器控制电压来控制振荡频率。在接收模式中，由于Q 8 和Q 9 切断Q 5 并且导通Q 4 ，所以发射/ 接收管脚设置为高电平。在发射模式中，发射/接收管脚设置为低电平。Q4 和Q5 的输出通过Q7被放大并被发送到缓冲放大器。3) 失锁检测器如果IC1的LD管脚上出现高电平，则产生失锁状态，并从D2,R4获得直流电压，且C12产生的提供给微处理器UL管脚的电压降低。当微处理器检测到此情况时，不能进行发射，无视通话转换开关输入信号。(参见图5)4. 发射部1) 发射音频来自于话筒的调制信号通过IC308 (A/4) 被放大，经过一个预加重电路，并通过另一个IC308 (B/4) 放大后进行IDC处理。然后信号通过一个低通滤波器 (分离滤波器) IC308 (C/4和D/4) 并滤除比3kHz频率更高的部分。得到的信号进入压控振荡器直接进行调频调制。(参见图6)2) QT/DQT编码器QT/DQT编码所需的信号通过IC300产生，被锁相环电路的基准频率调整。由于基准振荡器不能对频率环路特性外的频率进行调制，因此通过分配器在压控振荡器一侧进行调制。(参见图6)