Kenwood TK-7150 - Manual (Page 12)

TK-7150
12
CIRCUIT DESCRIPTION
1. Outline
The TK-7150 is a VHF/FM transceiver designed to operate
in the frequency range of 136 to 174MHz. Transmission out-
put power is 50 watts. The maximum channel capacity is
128.
The unit consists of receiver, transmitter, phase-locked
loop (PLL) frequency synthesizer, and control circuits.
2. Receiver Circuit
The receiver is double conversion superheterodyne, de-
signed to operate in the frequency range of 136MHz to
174MHz.
The receiver circuit consists of the following : 2-1 front-
end circuit, 2-2 first mixer, 2-3 IF amplifier circuit, 2-4 audio
amplifier circuit, and 2-5 squelch circuit.
2-1. Front-end Circuit
The front-end circuit consists of former BPF (D209), RF
amplifier Q213, and latter BPF (D208 and D207). The BPF
covers frequency ranges 136 to 174MHz.
The latter BPF (D208 and D207) attenuates the unwanted
signals, and sends only the necessary signal to the first
mixer.
2-2. First Mixer
The signal from the BPF is heterodyned with the first local
oscillator signal from the PLL frequency synthesizer circuit at
the first mixer DBM (Q209, Q210, Q211 and Q212) to be-
come a 44.85MHz first intermediate frequency (IF) signal.
The first IF signal is fed through two monolithic crystal filters
(XF201; Wide, XF202; Narrow) to further remove spurious
signals.
2-3. IF Amplifier
The first IF signal is amplified by Q207 and Q206, and then
enters IC201 (FM system IC). The signal is heterodyned
again with a second local oscillator signal (44.395MHz) with
in IC201 to become a 455kHz second IF signal. The second
IF signal is fed through a 455kHz ceramic filters (CF201 and
CF203; Wide, CF202 and CF204; Narrow) to further eliminate
unwanted signal, and the quadrature detection circuit FM-de-
tects the signal to produce a base-band signal and output it
from pin 9.
SW
W/N
MCF (Narrow)
XF202
MCF (Wide)
XF201
IF AMP
Q207
D206 D205
IF AMP
Q206
44.850MHz
SW
W/N
SW
W/N
CF202,204
(Narrow)
CF201,203
(Wide)
D204 D203
455kHz
DET
NOISE DET
D202
SW
W/N
Q205
SW
W/N
SW SW AMP
44.85MHz
1st MIX DBM
Q209~212
BPF
D207,208
RF AMP
Q213
BPF
D209
NOISE
AMP
Q204
QUD
FM SYSTEM IC : IC201
RSSI
DET
SQL
X201
44.395MHz
Q509
Buff AMP
Q513,515
RF AMP
Q208
LPF
f RX +44.85MHz
RX VCO
AMP
IC712 (A/2)
AINR AOUTR
CODEC
IC713
CPU
IC701
IC714
DEO
LPF
IC716 (A/2) IC724 IC722
MUTE
Q711 IC717
AF
AMP
IC720
RXO RXI AFO
DAC
IC718
ASQ
RSSI
INT. SP
RX ANT
TX-RX UNIT (X57-657)
Fig. 1 Receiver circuit