Kenwood NX-220 Service Manual

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NX-22020by the current flowing through the RF power amplifier andthis voltage is applied to the differential amplifier (IC1011/2). IC101 (2/2) compares the output voltage of IC101 (1/2)with the reference voltage from IC610, and the output ofIC101 (2/2) controls the VGG of Q103 and Q104 to make theboth current constant. The change of power high/low is car-ried out by the change of the reference voltage. Q106, Q107and Q108 are turned on and Q105 and Q109 are turned offduring transmission and the APC circuit is active.Fig. 5 Drive and final amplifier and APC circuit / 图 5 驱动器和末级放大器和 APC 电路fromT/R SW (D413)DriveAMPPre-DriveAMPQ102 Q103FinalAMPQ104ANTSW LPFD102,D103ANTVGGIC101(1/2)IC101(2/2)R153R154R155+BReference voltagefrom IC610VCC for Pre-Drive AMPfrom PD SW (Q110)5. PLL Frequency Synthesizer5-1. TCXO (X401)The TCXO (X401) generates a reference frequency of16.8MHz for the PLL frequency synthesizer. This referencefrequency is applied to pin 9 of the PLL IC (IC403) and isconnected to the IF circuit as a 2nd local signal through theTripler (Q301).The frequency adjustment is achieved by switching theratio of dividing frequency. The resolution of the adjustingfrequency is approximately 4Hz.5-2. VCOThere is a RX VCO and a TX VCO.The TX VCO (Q402) generates a transmit carrier and theRX VCO (Q401) generates a 1st local signal. For the VCOoscillation frequency, the transmit carrier is 136 to 174MHzand the 1st local receive signal is 185.95 to 223.95MHz.The VCO oscillation frequency is determined by one sys-tem of operation switching terminal “T/R” and two systemsof voltage control terminals “CV” and “ASSIST”.The operation switching terminal, “T/R”, is controlled bythe control line (/T_R) output from the ASIC (IC610). Whenthe /T_R logic is low, the VCO outputs the transmit carrierand when it is high, it outputs a 1st local receive signal.The voltage control terminals, “CV” and “ASSIST”, arecontrolled by the PLL IC (IC403) and ASIC (IC610) and theoutput frequency changes continuously according to theapplied voltage. For the modulation input terminal, “VCO_MOD”, the output frequency changes according to theapplied voltage. This is used to modulate the VCO output.“VCO_MOD” works only when “/T_R” is low.CIRCUIT DESCRIPTION / 电路说明1/2) 上。I C101(2/2) 将 I C101(1/2) 的输出电压与 I C610 的基准电压进行比较，同时 I C101(2/2) 的输出信号对 Q103 和Q104 的 V G G 进行控制，使两者的电流保持恒定。功率高 / 低的变化通过基准电压的变化来执行。在发射时 Q106、Q107 及Q108 开启，Q105 和 Q109 关闭，同时 APC 电路激活。5. PLL 频率合成器5-1. TCXO(X401)TCXO(X401) 生成 16.8MHz PLL 频率合成器的基准频率。该基准频率作为第 2 本振信号通过三倍频器 ( Q301)，被加载到PLL IC(IC403) 的第 9 脚并送至 IF 电路。通过切换分频比进行频率调整。调整频率的分辨率约为4Hz。5-2. VCO设有一个 RX VCO 和一个 TX VCO。TX VCO(Q402) 生成发射载波，RX VCO(Q401) 生成第 1 本振信号。对于 V C O 震荡频率，发射载波为 136 至 174M H z，第 1本振接收信号为 185.95 至 223.95MHz。V C O 震荡频率由一个操作切换端子“T / R”系统和两个电压控制端子“CV”和“ASSIST”系统确定。操作切换端子“T/R”由 ASIC(IC610) 控制线路 (/T_R) 的输出信号进行控制。/T_R 逻辑低时，VCO 输出发射载波；高时，输出第 1 本振接收信号。电压控制端子“C V”和“A S S I S T”由 P L L I C ( I C403) 和A S I C ( I C610) 控制，输出频率根据加载的电压持续改变。对于调制输入端子“VCO_MOD”，输出频率根据加载的电压改变。籍此调制 VCO 输出。“VCO_MOD”仅在“/T_R”低时工作。