Kenwood TK-8180 - Manual (Page 16)

TK-8180
16
1. Outline
The TK-8180 is a UHF/FM transceiver designed to operate
in the frequency range of 450 to 520MHz. Transmission out-
put power is 30 watts (490~520MHz : 25W). The maximum
channel capacity is 512.
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
520MHz.
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 HPF (D107, D108,
D109 and D110), RF amplifier Q103, and latter BPF (D103,
D104, D105 and D106). The BPF covers frequency ranges
450 to 520MHz.
The latter BPF (D103, D104, D105 and D106) 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 (IC171) to become a 44.85MHz first in-
termediate frequency (IF) signal. The first IF signal is fed
through a monolithic crystal filter (XF171) to further remove
spurious signals.
2-3. IF Amplifier
The first IF signal is amplified by Q171 and Q172, and then
enters IC172 (FM system IC). The signal is heterodyned
again with a second local oscillator signal (44.395MHz) with
in IC172 to become a 455kHz second IF signal. The second
IF signal is fed through a 455kHz ceramic filters (CF172;
Wide, CF171; Narrow) to further eliminate unwanted signal,
and the quadrature detection circuit FM-detects the signal to
produce a base-band signal and output it from pin 9.
2-4. Audio Amplifier
The demodulated audio signal from IC172 goes to IC415
through the AF amplifier (IC412) and IC413. The audio signal
goes to an electronic volume (IC410) and is amplified to drive
a loudspeaker by an audio power amplifier (IC417). The audio
output can be provided to external 4
Ω speaker through the
speaker jack output (J401) on the rear panel. Q419 is a mute
switch.
IF AMP
Q172
IF AMP
Q171
SW
CFSW
CF171
(Narrow)
CF172
(Wide)
D171 D172
455kHz
DET
NOISE DET
D173
SW
W/N
Q178
SW
CFSW
44.85MHz
1st MIX DBM
IC171
BPF
D103~D106
RF AMP
Q103
HPF
D107~D110
NOISE
AMP
Q175
QUD
FM SYSTEM IC : IC172
RSSI
DET
SQL
X171
44.395MHz
Q306
Buff AMP
Q311
Buff AMP
Q313
LPF
f RX –44.85MHz
RX VCO
AMP
IC412 (B/2)
AQUA
-L
IC415
CPU
IC404
IC407
DEO
MUTE
Q419
AF
AMP
IC417
AFO
DAC
IC410
SW
IC413
DAC
IC410
ASQ
RSSI
INT. SP
450~520MHz
RX ANT
TX-RX UNIT (X57-699)
MCF MCF
XF171
(2/2)
XF171
(1/2)
405.15~475.15MHz
CIRCUIT DESCRIPTION
Fig. 1 Receiver circuit