15
TK-2118
TK-260
:K, K2
Fig. 6 Transmit audio QT/DQT /
图6 发射音频QT/DQT
MUTE
VR302
MAX
DEV
BALANCE
X1, IC1
VR301
VCO
REFERENCE
OSC
(TCXO)
MIC
IC308 (A/4)
MIC
AMP
IC308 (B/4)
IDC
Q322
SW
PREEMPHASIS
IC308(C/4, D/4)
LPF
(SPLATTER FILTER)
IC300
TO
QT/DQT
CIRCUIT DESCRIPTION /
电路说明
3) VCO and RF amplifier
The transmit signal obtained from the VCO buffer amplifier
Q11, is amplified by Q15. This amplified signal is passed to
the power amplifier, Q18 and Q22, which consists of a 2-stage
FET amplifier and is capable of producing up to 5W of RF
power. (See Fig.7)
4) ANT switch and LPF
The RF amplifier output signal is passed through a low-
pass filter network and a transmit/receive switching circuit
before it is passed to the antenna terminal. The transmit/
receive switching circuit is comprised of D24, D25, D26 and
D27. D25 and D26 turned on (conductive) in transmit mode
and off (isolated) in receive mode.
Fig. 7 APC system /
图7 自动功率控制系统
AMP
Q15
DRIVE AMP
Q18
5T
B
DET
IC3
APC
5T
Q23
SW
Q16
SW
APC
5T
Q17
SW
RX
D25, 26
ANT SW
FINAL AMP
Q22
ANT SW
D24, 27
LPF
ANT
5T
SW
Q14
TH1
3) 压控振荡器和射频放大器
从压控振荡缓冲放大器(Q11)接收到的发送信号通过Q15被放
大。这个放大信号通过功率放大器，Q18和Q22 (包括一个二级
场效应管放大器)，并能产生５W射频功率。(参见图7)
4) 天线转换开关和LPF
在其到达天线终端之前，射频放大器输出信号通过一个低通
滤波器网络和一个发射/ 接收转换电路。发射/ 接收转换电路由
D24, D25, D26和D27构成。D25和D26在发射模式下开启 (通
导)，在接收模式下关闭 (隔离)。
