Circuit Description - Kenwood TK-190 Service Manual

TK-190
1. Overview
The KENWOOD model TK-190 is a VHF/FM hand-held
transceiver designed to operate in the frequency range of
29.7 to 37MHz(K),35.0 to 50.0MHz(K2), the unit consists of
a receiver, a transmitter, a phase-locked loop(PLL) fre-
quency synthesizer, power supply circuit, a control unit.
2. Circuit Configuration by Frequency
The receiver is a double-conversion super-heterodyne
with a first intermediate frequency (IF) of 128.55MHz and a
second IF of 455kHz. Incoming a signals from the antenna
are mixed with the local signal from the PLL1 to produce the
first IF of 128.55MHz.
This is then mixed with the 129.005MHz seconds local
oscillator output to produce the 455kHz second IF. This is
detected to give the demodulated signal.
T h e t r a n s m i t s i g n a l i s m o d u l a t e d P L L 2 -
VCO2(129.005MHz) from the microphone. The transmit sig-
nal frequency is down-conversion with PLL2 and PLL1. It is
then amplified and sent to the antenna.
ANT
TX/RX
29.7~37.0MHz : K
35.0~50.0MHz : K2
1st MIX
ANT ANT
SW SW
158.25~165.55MHz : K
163.55~178.55MHz : K2
TX MIX
PA TX
AMP AMP
29.7~37.0MHz : K
35.0~50.0MHz : K2
Fig. 1 Frequency configuration
3. Receiver System
3-1. Front-end RF amplifier
The signal are then passed through an antenna matching
coil, where the high-frequency components are amplified by
a MES FET(Q200). The signals are then fed into band-pass
filter that uses varactor diode tuning to reject unwanted sig-
nal components, and is fed to the 1st mixer.
3-2. First mixer
The 1st mixer uses the GaAs IC (IC200). The 1st mixer
mixes the signal with the 1st local oscillator frequency from
the VCO1, and converts to the 1st IF (128.55MHz).
The signal then passes through monolithic crystal filter
(XF300) to remove unnecessary nearby frequency compo-
nents. The signal from the MCF is used as the 1st IF signal.
12

CIRCUIT DESCRIPTION

CF
455kHz
MCF
128.55MHz
FM IF AF
SYSTEM AMP
PLL2
VCO2
158.705 ~166.005MHz : K
164.005 ~179.005MHz : K2
129.005MHz
PLL1 MIC
VCO1 AMP
129.005MHz
3-3. IF amplifier
The 1st IF signal is amplified (Q302) and fed into IC300 in
the FM IC. The IF signal is then mixed with the 2nd local
oscillator frequency of 129.005MHz to generate the 2nd IF
of 455kHz. The 455kHz signal is then passed through a ce-
ramic filter (CF300) and fed back into IC300 for additional
amplification.
Q200
BPF RF AMP
MCF
128.55MHz
Fig. 2 Receiver section
Item
SP
Nominal center frequency
Pass band width
Attenuation band width
Ripple
Insertion loss
MIC
Guaranteed attenuation
Terminating impedance
Table 1 Crystal filter XF300 (L71-0559-05)
1st MIX
BPF BPF LPF
Q302
IF AMP
IC300
FM IF SYSTEM
CF300
455kHz
129.005MHz
Rating
128.55MHz
± 5~7kHz or more at 3dB
± 25kHz or less at 3dB
1.0dB or less
6dB or less
80dB or more at fo± 910kHz
40dB or more within fo± 1MHz
600Ω
D102
T/R
SW