Circuit Description - Kenwood TK-P701 Service Manual

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.
TX/RX: 136~174MHz
ANT
ANT
SW
TX
AMP
2. Receiver System
The receiver system is shown in Figure 2.
ANT
Q204
BPF RF AMP
ANT
SW
BPF
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).

CIRCUIT DESCRIPTION

1st MIX MCF
RF
AMP
38.85MHz
174.85~
212.85MHz
RF
AMP
136~174MHz
Fig. 1 Frequency confi guration
Q203
BPF 1st MIX XF200
MCF
BPF 1st Local
Fig. 2 Receiver system
CF
450kHz
IF AF
SYSTEM filter
38.4MHz
X2
TCXO 19.2MHz
doubler
PLL MIC
VCO AMP
CF200
Q202
IF AMP
IC200
IF,MIX,DET
Q201
X2 doubler
2nd Local
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.
TK-P701
SP
AF
AMP
MIC
IC303
IC302
AFfilter VR500 AF PA SP
X1
TCXO
19.2MHz
7