Kenwood TK-2217 Service Manual page 28

(2) DTMF
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
(IC301). 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 IC301. And is routed to the VCO.
When encoding MSK, the microphone input signal is muted.
5. Power Supply
There are four 5V power supplies 5M,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 (IC405) and
its peripheral circuits. It controls the TX-RX unit and transfers
data to the Display unit. IC405 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.
(3) Sending frequency program data to the PLL.
(4) Controlling squelch on/off by the DC voltage from the
squelch circuit.
(5) Controlling the audio mute circuit by the decode data
input.
(6) Transmitting tone and encode data.
1) Frequency Shift Circuit
The microprocessor (IC405) operates at a clock of
7.3728MHz. This oscillator has a circuit that shifts the
frequency by beat shift switch (Q407,Q408).
A beat sound may be able to be evaded from generation if
"Beat Shift" is set to ON when it is generated in the internal
spurious transmission modulated sound of a transceiver.
CIRCUIT DESCRIPTION /
X3
Q408
H:OFF
L : ON
Fig. 8 Frequency shift circuit / 图 8 频率偏移电路
电路说明
(2) DTMF
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 (IC301)。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
IC301 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
有 4 个 5V 电源: 5M,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 4 0 5 )和外部电路构成。它控制
TX-RX 单元和传送数据到显示单元。IC405 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。
(3) 发送频率数据给 PLL。
(4) 根据静噪电路输出的 DC 电压来控制静噪的开启和关闭。
(5) 根据解码数据控制音频静音。
(6) 发射 Tone 及编码数据。
1) 频率偏移电路
微处理器 (IC405) 在 7.3728MHz 时钟下工作。此振荡器有可
以被拍频偏移开关 (Q407, Q408) 变换频率的电路。
如果"Beat Shift (拍频偏移)"被设定为 ON，可以避免产生拍
频声音。
11
XOUT
IC405
8
BSHIFT
Q407
H:OFF
L : ON
TK-2217
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