Circuit Description - Kenwood TK-3360 Service Manual

1. Overview
The TK-3360 is a UHF portable transceiver designed to
operate in the frequency range of 450~520MHz. The unit
consists of a receiver, transmitter, phase-locked loop (PLL)
frequency synthesizer, base band parts, power supply and
control circuits.
TX/RX: 450~520MHz
ANT
ANT
SW
TX
AMP
3. Receiver System
The receiver system is shown in Figure 2.
ANT
BPF
ANT
SW
TUNE
3-1. Front End (RF Amplifi er) Circuit
The signal coming from the antenna passes through the
transmit / receive switching diode circuit (D201, D202, D203
and D204) and a BPF (L418 and L419), and is then amplifi ed
by the RF amplifi er (Q407).
The resulting signal passes through a BPF (L413, L414
and L440) and goes to the mixer. These BPFs are adjusted
by variable capacitors (D431, D410, D403, D404 and D405).
The input voltage to the variable capacitor is a regulated
voltage output from the DC amplifi er (IC811).

CIRCUIT DESCRIPTION

1st MIX MCF
RF
AMP
49.95MHz
400.05~
470.05MHz
RF
AMP
450~520MHz
Fig. 1 Frequency confi guration
Q407 Q406
RF AMP BPF 1st MIX
TUNE 1st Local
Fig. 2 Receiver system
2. Frequency Confi guration
The receiver utilizes double conversion. The first IF is
49.95MHz 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.
CF
450kHz
IF Audio
SYSTEM processor
50.4MHz
X3
TCXO
multiply
PLL
VCO
CF401
CF402
Q405
XF401 IF AMP
IC401
IF,MIX,DET
MCF
Q403
X3 multiply
2nd Local
3-2. First Mixer
The signal from the front end is mixed with the fi rst local
oscillator signal generated in the PLL circuit by Q406 to pro-
duce a fi rst IF frequency of 49.95 MHz.
The resulting signal passes through the XF401 MCF to
cut the adjacent spurious and provide the optimum charac-
teristics, such as adjacent frequency selectivity.
TK-3360
SP
AF
AMP
16.8MHz
MIC
MIC
AMP
IC815
IC812 AF PA
Audio
processor
X1
TCXO
16.8MHz
SP
9