Kenwood TM-D700A Service Manual page 4

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
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