Circuit Description - Kenwood TK-3302 Service Manual

TK-3302
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 oscil-
lator signal is supplied from the PLL circuit.
The PLL circuit in the transmitter generates the neces-
sary frequencies. Fig. 1 shows the frequencies.
TX/RX :
ANT
1st MIX
RF
ANT
AMP
SW
38.85MHz
RX:
TX
AMP
TX:
Model Type
TK-3302 E,T 440~470MHz 440~470MHz
TK-3302 E3 400~430MHz 400~430MHz
Fig. 1 Frequency confi guration
2. Receiver
The frequency confi guration of the receiver is shown in
Fig. 2.
ANT RF AMP
BPF
Q204
ANT
SW
RCTV
CF201
IC201
IF, MIX, DET AQUA-L
Q2
X3 multiply TXCO
2nd Local 12.8MHz
Fig. 2 Receiver section
■ Front End (RF AMP)
The signal coming from the antenna passes through the
transmit/receive switching diode circuit, (D103, D104 and
D105) passes through a BPF (L213 and L212), and is ampli-
fi ed by the RF amplifi er (Q204).
8

CIRCUIT DESCRIPTION

CF
450kHz
MCF
IF AF
SYSTEM AMP
38.4MHz
X3
TCXO 12.8MHz
multiply
RF PLL
MIC
AMP
AMP VCO
q w
401.15~
431.15MHz
361.15~
391.15MHz
MIXER MCF
BPF
Q203 XF201
PCTV 1st Local
IC309
AF VOL SP
AF PA
IC308
X1
The resulting signal passes through a BPF (L209, L207
and L206) and goes to the mixer. These BPFs are adjusted
by variable capacitors (D201, D202, D203, D204 and D205).
The input voltage to the variable capacitor is regulated by
voltage output from the MCU (IC306).
■ 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 38.85MHz.
The resulting signal passes through the XF201 MCF to
SP
cut the adjacent spurious and provide the opitimun charac-
teristics, such as adjacent frequency selectivity.
■ IF Amplifi er Circuit
The fi rst IF signal is passed through a four-pole monolithic
crystal fi lter (XF201) to remove the adjacent channel signal.
MIC
The fi ltered fi rst IF signal is amplifi ed by the fi rst IF ampli-
fier (Q202) and then applied to the lF system IC (IC201).
The IF system IC provides a second mixer, limiting amplifi er,
quadrature detector and RSSI (Received Signal Strength In-
e
dicator). The second mixer mixes the fi rst IF signal with the
38.4MHz of the second local oscillator output (TCXO X1 and
Q2) and produces the second IF signal of 450kHz.
The second IF signal is passed through the ceramic fi lter
(CF201) to remove the adjacent channel signal. The fi ltered
second IF signal is amplified by the limiting amplifier and
demodulated by the quadrature detector with the ceramic
discriminator (CD201). The demodulated signal is routed to
the audio circuit.
■ Wide/Narrow Switching Circuit
Narrow and Wide settings can be made for each channel
by switching the demodulation level.
The WIDE (low level) and NARROW (high level) data is
IF AMP
output from IC306, pin 5. When a WIDE (low level) data is
Q202
received, Q201 turn on. When a NARROW (high level) data
is received, Q201 turn off.
Q201 turns on/off with the Wide/Narrow data and the
IC201 detector output level is switched to maintain a con-
stant output level during wide or narrow signals.
W/N
(IC306)
L : Wide
H: Narrow
Fig. 3 Wide/Narrow switching circuit
AFOUT
IC201
FM IF SYSTEM
QUAD IFOUT
R209
Q201
Q202
5R