TK-8150
12
CIRCUIT DESCRIPTION
1. Outline
The TK-8150 is a UHF/FM transceiver designed to operate
in the frequency range of 450 to 500MHz. Transmission out-
put power is 45 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 450MHz to
500MHz.
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 (D211 and
212), RF amplifier Q214, and latter BPF (D207, D208, D209
and D210). The BPF covers frequency ranges 450 to
500MHz.
The latter BPF (D207, D208, D209 and D210) 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 (Q210, Q211, Q212 and Q213) to be-
come a 73.05MHz 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 (73.505MHz) 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
73.05MHz
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
73.05MHz
1st MIX DBM
Q210~213
BPF
D207~210
RF AMP
Q214
BPF
D211,212
NOISE
AMP
Q204
QUD
FM SYSTEM IC : IC201
RSSI
DET
SQL
X201
73.505MHz
Q508
Buff AMP
Q513,515
RF AMP
Q208
RF AMP
Q209
LPF
f
RX
–73.05MHz
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
AFO
RXI
DAC
IC718
ASQ
RSSI
INT. SP
RX ANT
TX-RX UNIT (X57-658)
Fig. 1
Receiver circuit