Kenwood TK-P701, Service Manual

Page: 7 / 38

TK-P701
7
1. Frequency Confi guration
The receiver utilizes double conversion. The first IF is
38.85MHz and the second IF is 450kHz. The fi rst 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 confi guration
Fig. 2 Receiver system
2-1. RF Amplifi er Circuit
The signal coming from the antenna passes through the
transmit/receive switching diode circuit (D101, D102, and
D103) and a BPF (L210), and is then amplifi ed by the RF
amplifi er (Q204).
The resulting signal passes through a BPF (L207, L208
and L215) and goes to the mixer. These BPFs are adjusted
by variable capacitors (D201,D202 and D204). The input
voltage to the variable capacitor is a regulated voltage out-
put from the DAC (IC300).
2-2. First Mixer
The signal from the front end is mixed with the fi rst local
oscillator signal generated in the PLL circuit by Q203 to pro-
duce a fi rst 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: 136~174MHz
174.85~
212.85MHz
136~174MHz
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 1 9 .2MHz
SP
ANT
IC200
IF,MIX,DET
Q203
1st MIX
IC303
CF200
ANT
SW
Q201
X2 doubler
2nd Local
X1
TCXO
1 9 .2MHz
BPF
BPF
Q204
RF AMP XF200
MCF
Q202
IF AMP
IC302
AF PA
BPF 1st Local
BPF AFfilter VR500