Circuit Description - Kenwood TK-6110 Service Manual

1. Overview
The KENWOOD model TK-6110 is a VHF/FM 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 re-
ceiver, a transmitter, a phase-locked loop (PLL) frequency
synthesizer, power supply circuits, a control unit.
2. Circuit Configuration by Frequency
The receiver is a double-conversion superheterodyne
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.
The transmit signal is modulated PLL2-VCO2 (129.005
MHz) from the microphone. The transmit signal 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
MCF
1st MIX 128.55MHz
ANT
LPF
SW
29.7~
37.0MHz : K
TX MIX
35.0~
50.0MHz : K2
PA
TX
AMP
AMP
Fig. 1 Frequency configuration

CIRCUIT DESCRIPTION

CF
455kHz
FM IF AF
SYSTEM AMP
129.005
MHz
PLL2 MIC
AMP
VCO2
129.005
MHz
158.705~166.005MHz : K
164.005~179.005MHz : K2
PLL1
VCO1
158.25~165.55MHz : K
163.55~178.55MHz : K2
3. Receiver System
3-1. Front-End RF Amplifier
An incoming signal from the antenna is applied to a band-
pass filter (L202) after going through a low-pass filter and an
antenna switch (K1). The signal is then amplified by the RF
amplifier (Q201) and again filtered by another band-pass fil-
ter (L203, L206 and L207).
3-2. First Mixer
The signal from the band-pass filter is heterodyned with
the first local oscillator signal from the PLL frequency syn-
thesizer circuit at the first mixer (IC201) to become a
128.55MHz first intermediate frequency (IF) signal.
The first IF signal is fed through two monolithic crystal
filters (XF201) to further remove spurious signals.
3-3. IF Amplifier
The first IF signal is amplified by Q202 and Q205, and
then enters IC202 (FM processing IC). The signal is hetero-
dyned again with a second local oscillator signal
(129.005MHz) with in IC202 to become a 455kHz second IF
signal. The second IF signal is fed through a 455kHz ce-
ramic filter, CF201 and CF202 to further eliminate unwanted
signals before it is amplified and FM detected in IC202.
Q201
BPF RF AMP
SP
Q202
MCF
IF AMP 128.55MHz
MIC
XF201
Fig. 2 Receiver section
Item
Nominal center frequency
Pass bandwidth
Attenuation bandwidth
Ripple
Insertion loss
Guaranteed attenuation
Terminating impedance
Table 1 Crystal filter (L71-0560-05)
(TX-RX unit XF201)
TK-6110
IC201
1st MIX
BPF BPF LPF
Q205
IF AMP
IC202
FM IF SYSTEM
CF201,202
129.005MHz 455kHz
Rating
128.55MHz
7.5kHz or more at 3dB
35kHz or less at 40dB
1.0dB or less
5dB or less
70dB or more at fo 910kHz
1000
D502
T/R
SW
13