Kenwood TK-3160 Service Manual page 16

3) APC Circuit
The APC circuit always monitors the current flowing through
the RF power amplifier (Q211) and keeps a constant current.
The voltage drop at R256, R257 and R261 is caused by the
current flowing through the RF power amplifier and this
voltage is applied to the differential amplifier IC201(1/2).
IC201(2/2) compares the output voltage of IC201(1/2) with
the reference voltage from IC805. The output of IC201(2/2)
controls the VG of the RF power amplifier, drive amplifier
and pre-drive amplifier to make both voltages the same.
The change of power high/low is carried out by the change
of the reference voltage.
4) Encode Signalling
(1) QT/DQT
QT,DQT data of the LSDTCXO Line is output from pin 22 of
the CPU. The signal passes through a low-pass CR filter
and goes to the TCXO(X1).
The QT,DQT data of the LSDVCO Line is output from pin
20 of the CPU. The signal passes through a low pass CR
filter, mixes with the audio signal, and goes to the VCO
modulation input. TX deviation is adjusted by the CPU.
(2) DTMF/2-tone
High-speed data is output from pin 2 of the CPU. The signal
passes through a low-pass CR filter, and provides a TX and
SP out tone, and is then applied to the audio processor
(IC601). The signal is mixed with the audio signal and goes
to the VCO.
TX deviation is adjusted by the CPU.
(3) MSK (Fleet Sync)
Fleet Sync utilizes 1200bps and 2400bps MSK signal is
output from pin 6 of IC601. And is routed to the VCO.
When encoding MSK, the microphone input signal is muted.
5. Power Supply
There are 3.5V power supply for PLL circuit and five 5V
power supplies 5M, 5MS, 5C, 5R, and 5T. 5M for
microprocessor is always output while the power is on. 5M is
always output, but turns off when the power is turned off to
prevent malfunction of the microprocessor.
5C is a common 5V and is output when SAVE is not set to
OFF.
5R is 5V for reception and output during reception.
5T is 5V for transmission and output during transmission.
6. Control Circuit
The control circuit consists of a microprocessor (IC805) and
its peripheral circuits. It controls the TX-RX unit. IC805 mainly
performs the following:
(1) Switching between transmission and reception by the
PTT signal input.
(2) Reading system, group, frequency, and program data
from the memory circuit.
CIRCUIT DESCRIPTION /
电路说明
3) 自动功率控制 (APC) 电路
APC 电路一直监视通过射频功率放大器 (Q211) 的电流并保
持电流稳定。经过射频功率放大器的电流的变化会引起
R256， R257和R261的电压降低， 此电压送到差分放大器 IC201
(1/2) 。
IC201 (2/2) 将IC201 (1/2) 的输出电压与来自IC805的参考电压
进行比较。
IC201 (2/2) 的输出电压控制射频功率放大器， 驱动放大器， 预
驱动放大器的 VG，使电压保持一致。
功率高 / 低的变化是通过变更参考电压来实现的。
4) 编码信令
(1) QT/DQT
LLSDTCXO 线的 QT,DQT 数据从 CPU 的 22 管脚输出。信号通
过低通 CR 滤波器，并且送到 TCXO (X1)。
LSDVCO 线的 QT, DQT 数据从 CPU 的 20 管脚输出。信号通过
低通 CR 滤波器，与音频信号混合，然后输入到 VCO。TX 频
偏被 CPU 调整。
(2) DTMF/2-tone
高速数据从 CPU 的 2 脚输出。 信号通过低通 CR 滤波器，提供
TX 和 SP 输出音频，并输入到音频处理器 (IC601)。信号与音
频信号混合，然后送到 VCO。
TX 频偏被 CPU 调整。
(3) MSK ( Fleet Sync)
FleetSync 使用 1200bps 和 2400bps 的 MSK 信号，这些信号从
IC601 的 6 脚输出。并且被发送到 VCO。当编码 MSK 时，话
筒输入信号被静音。
5 . 电源
本机用 3.5V 电源提供给 PLL 电路，并用 5 个 5V 电源提供给
5M, 5MS, 5C, 5R 和 5T。当电源接通时，微处理器用的 5M 一直
保持输出。5M 虽然为经常输出，但在关闭电源时也被关掉，防
止微处理器出现故障状态。
5C 为公共的 5V，在非省电状态时保持输出。
5R 为接收用的 5V，在接收期间保持输出。
5T 为发射用的 5V，在发射期间保持输出。
6 . 控制电路
控制电路是由微处理器( I C 8 0 5 ) 和外部电路构成。它控制
TX-RX 单元。IC805 的主要功能如下：
(1) 根据 PTT 的输入信号来转换发射和接收状态。
(2) 从存储电路读出系统，组，频率以及编程数据。
TK-3160
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