TK-3501
6
1. Frequency Configuration
The receiver utilizes double conversion. The first IF is
38.85MHz and the second IF is 450kHz. The first Local os-
cillator is supplied from the PLL circuit.
The PLL circuit in the transmitter generates the neces-
sary frequencies.
CIRCUIT DESCRIPTION
2. Receiver System
The receiver system is shown in Figure 2.
Fig. 1 Frequency configuration
Fig. 2 Receiver system
2-1. Front End (RF Amplifier) Circuit
The signal coming from the antenna passes through the
transmit/receive switching diode circuit (D102 and D103)
and a BPF, and is then amplified by the RF amplifier (Q204).
The resulting signal passes through a BPF and goes to
the mixer.
2-2. First Mixer
The signal from the front end is mixed with the first local
oscillator signal generated in the PLL circuit by Q203 to pro-
duce a first IF frequency of 38.85 MHz.
The resulting signal passes through the XF200 MCF to
cut the adjacent spurious and provide the optimum charac-
teristics, such as adjacent frequency selectivity.
TX/RX: 446.00~446.10MHz
1st MIX
MCF
SP
MIC
CF
450kHz
ANT
ANT
SW
RF
AMP
IF
SYSTEM
X2
doubler
PLL
VCO
38.85MHz
38.4MHz
TX
AMP
RF
AMP
AF
AMP
MIC
AMP
AF
filter
TCXO
19.2MHz
407.15~407.25MHz
446.00~446.10MHz
EXT SP
ANT
IC200
IF,MIX,DET
Q203
1st MIX
IC303,
IC620
CF200
ANT
SW
Q201
X2 doubler
2nd Local
X1
TCXO
19.2MHz
BPF
Q204
RF AMP
XF200
MCF
Q202
IF AMP
IC302
AF PA
INT SP
IC601
AF PA
1st Local
BPF
AFfilter
VR500
