Kenwood TM-D700A Service Manual

TM-D700A/E
CIRCUIT DESCRIPTION
2. Receiver system
2-1.Main VHF Receiver
The incoming signal from the antenna passes through a
filter circuit and goes to the RF amplifier (Q205). The amplified
signal enters the helical resonator (L209, L207, L204). The
helical resonator is tuned to the desired frequency according to
the BPF voltage output from the CPU with the varicap (D206,
D205, D202). After the signal passes through a filter, it is
amplified by another RF amplifier (Q202) and goes to the
single balanced mixer (Q200, Q201). The frequency of the
ANT
Y LPF AF AMP BPF RF AMP
he Q205 mt
— 3SK239A aS
L209,L207,L204
D206
D205
D202
TUNE BY VOLTAGE
CPU
signal is converted by the first local oscillator (Upper
heterodyne) to generate a 38.85MH first IF signal. The signal
passes through the MCF (XF100), is amplified by the IF
amplifier (Q112) and enters the IF IC (IC100). Then the signal
is converted to the 450kHz second IF signal by the second
iocal oscillator, which is tripled 12.8MHz (Lower heterodyne).
Then it is detected to generate an audio signal.
SINGLE BALANCED
MIXER
IF AMP
> AF
Q102
2804649) x3
(N.P)
12.8BMHz
Fig.2 Main VHF Receiver circuit
2-2.Main UHF Receiver
The incoming signal from the antenna passes through a
filter circuit and enters the RF amplifier (Q508). The amplified
signal passes through the SAW filter (L517), is amplified by
another RF amplifier (Q505). Then it passes through the LC
filter (L508) and enters the single balanced mixer (Q501,
Q502). The frequency of the signal is converted by the first
LC BPF
local
oscillator
(Lower
heterodyne)
to
generate
a
45.05MHz
first
IF
signal.
The
signal
passes
through
the
MCF
(XF400),
is
amplified
by
the
IF
amplifier
(Q406)
and
enters
the
IF
IC
(IC400).
The
signal
is
converted
to
the
455kHz
second
IF
signal
by
the
second
local
oscillator
(Upper
heterodyne).
Then
itis
detected
to
generate
an
audio
signal.
SINGLE BALANCED
IXER
ANT
HPF LPF REAMP saweitteR REAMP
| | —~ ~h Q508 oo
eS PT 3SK239A =
b> AF
45.505MHz [7]
7
Fig.3 Main UHF Receiver circuit

Kenwood TM-D700A Specifications

General

Brand	Kenwood
Model	TM-D700A
Category	Transceiver
Language	English