Circuit Description - Kenwood TK-5210G Service Manual

TK-5210
1. Overview
The KENWOOD model TK-5210(G) is a VHF/FM/P25 Por-
table transceiver designed to operate in the frequency range
of 136 to 174MHz.
The unit consists of a receiver, a transmitter, a phase-
locked loop (PLL) frequency synthesizer, a digital control
unit, power supply circuit.
ANT
TX/RX: 136~174MHz
ANT
SW
PA
AMP
3. Receiver System
3-1. Front-end RF Amplifi er
The signal is passed through an antenna matching coil,
where the high-frequency components are amplified by a
GaAs FET (Q202). The signals are then fed into band-passfi l-
ter that uses varactor diode tuning to reject unwanted signal
components, and is fed to the 1st mixer.
3-2. 1st Mixer
The 1st mixer is used the GaAs IC (IC202). The 1st mixer
mixes the signal with the 1st local oscillator frequency from
the VCO, and converts it to the 1st IF (49.95MHz). The sig-
nal then passes through monolithic crystal fi lter (XF201) to
remove unnecessary nearby frequency components. The
signal from the MCF is used as the 1st IF signal.
18
( G )

CIRCUIT DESCRIPTION

1st MIX
RF
AMP
49.95MHz
16.8MHz
VCXO
185.95~223.95MHz
TX
AMP
136~174MHz
Fig. 1 Frequency confi guration
2. Frequency Confi guration
The receiver is a double-conversion super heterodyne
using first intermediate frequency (IF) of 49.95MHz and
second IF of 450kHz. Incoming signals from the antenna are
mixed with the local signal from the PLL circuit to produce
the fi rst IF of 49.95MHz.
This is then mixed with the 50.4MHz second local signal
to produce the 450kHz second IF. This signal is detected to
give the demodulated signal in the DSP.
The transmit signal frequency is generated by the PLL
VCO, and modulated by the signal from the DSP. It is then
amplifi ed and fed to the antenna.
CF
450kHz
MCF
MIX
IF AMP
x3
50.4MHz
PLL
VCO
3-3. IF Amplifi er
The 1st IF signal is amplifi ed by the IF amplifi er (Q204)
and fed into the FM IC (IC204). The IF signal is then mixed
with the 2nd local oscillator frequency of 50.4MHz to gener-
ate the 2nd IF of 450kHz. The 450kHz signal is then passed
through a ceramic fi lter (CF201) and fed back into IC204 for
additional amplifi cation.
3-4. Wide/Narrow/P25 Switching Circuit
Wide, Narrow, and P25 settings can be made for each
channel by switching the ceramic filters CF203 (Wide),
CF204 (Narrow, P25), and there are controlled with the mul-
tiplexers (IC206, IC207).
When a W_/N Signal line is H, the 450kHz signal is
passed through a ceramic fi lter (CF203).
When a W_/N signal line is L, the 450kHz signal is
passed through a ceramic fi lter (CF204).
After that, the signal throughs ceramic fi lter (CF250) and
is fed into ASIC (IC10). And then, the signal is demodulated
in ASIC, the AF signal is dealed with DSP (IC3).
SP
AF
AMP
MIC
MIC
AMP