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Circuit description, Outline, Receiver circuit – Kenwood TK-8180 User Manual

Page 16: Tk-8180

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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