Circuit Description - Kenwood TK-3501 Service Manual

TK-3501
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.
TX/RX: 446.00~446.10MHz
ANT
ANT
SW
TX
AMP
2. Receiver System
The receiver system is shown in Figure 2.
ANT
BPF
ANT
SW
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.
6

CIRCUIT DESCRIPTION

1st MIX MCF
RF
AMP
38.85MHz
407.15~407.25MHz
RF
AMP
446.00~446.10MHz
Fig. 1 Frequency configuration
Q204 Q203
RF AMP BPF 1st MIX
1st Local
Fig. 2 Receiver system
CF
450kHz
IF AF
SYSTEM filter
38.4MHz
X2
TCXO
doubler
PLL
VCO
CF200
Q202
XF200 IF AMP
IC200
IF,MIX,DET
MCF
X1 Q201
TCXO X2 doubler
19.2MHz 2nd Local
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.
SP
AF
AMP
19.2MHz
MIC
MIC
AMP
IC303,
IC620 IC302
AFfilter AF PA EXT SP
VR500
IC601
AF PA INT SP