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1. Overview
This transceiver is a VHF portable transceiver designed
to operate in the frequency range of 136 to 174MHz.
The unit consists of receiver, transmitter, phase-locked
loop (PLL) frequency synthesizer, base band parts, power
supply, and control circuits.
2. Frequency Configuration
The frequency configuration is shown in Figure 1 and
Table 1.
ANT
RX/TX:136 ~ 174MHz
MIX
RF
ANT SW
AMP
FINAL
PRE
DRIVE
DRIVE
Fig. 1 Frequency configuration
Double super heterodyne
Reception method
1st IF Frequency
2nd IF Frequency
Transmission method
VCO direct oscillation amplification
Modulation
Variable reactance phase modulation
Table 1 Basic configuration
3. Receiver
3-1-1.
Front-end RF Amplifier
The received signal from the antenna passes through a
low-pass filter and then through a transmission/reception
switching circuit (antenna switch) and enters the tuned
filter (L510).
The signal passing through the band-pass filter (L510) is
amplified by with an RF amplifier (Q505), passes through a
band-pass filter (L512, L542) and enters the first mixer
(Q506).
These band-pass filters are tuned to a desired frequency
by varicaps (D509, D510, D511,
A tuning voltage corresponding to the desired signal is
applied to each varicap through the VFO terminal (pin 60)
of the MPU (U206) to tune to the receive frequency.
3-1-2.
First Mixer
The received signal passing through the band-pass filter
CIRCUIT DESCRIPTION
CF
450KHz
MCF
AF
IF SYSTEM
AMP
38.850MHz
38.40MHz
Tripler
X3
19.200MHz
TCXO
MIC
PLL
AMP
VCO
38.85MHz (Upper)
450kHz (Lower)
D512).
(See Fig.2)
(L512, L542) is mixed with the first local signal generated
by the VCO by the first mixer (Q506) to produce a first IF
signal (38.85MHz) (Upper heterodyne).
The first IF signal passes through a MCF (Monolithic
crystal filter: XF500 and XF501) to remove unwanted
components.
The first IF signal passing through the MCF (XF500 and
XF501) is amplified by an IF amplifier (Q509) and the
resulting signal enters the FM IC
3-1-3.
IF Amplifier Circuit
The first IF signal (38.85MHz) amplified by the IF
SP
amplifier (Q509) and the second IF signal (45.9MHz)
generated by tripling the 19.200MHz reference oscillator
frequency of the TCXO (X500) by Q510, are mixed in the
FM IC to produce a second IF signal (450 kHz) (Lower
heterodyne).
MIC
The second IF signal passes through a ceramic filter
(CF500)
to remove unwanted components.
The second IF signal passing through the ceramic filter
(CF500) passes through the IF amplifier in the FM IC again
and is detected to produced an audio signal.(See Fig.2)
ANT
D503,D504
BPF
D517
ANT SW
CF500
IF,MIX,DET
U502
38.400MHz
X500
Q510
TCXO
Tri ple r X3
2nd Loca l OSC
3-1-4. Wide/Narrow Switching Circuit
Narrow and Wide settings can be made for each channel
by switching the demodulation level. The WIDE (low level)
and NARROW(high level) data is output from U206, pin 11.
When a WIDE (low level) data is received, Q507 turn on.
When a NARROW (high level) data is received, Q507
turn off.
Q507 turns on/off with the Wide/Narrow data and the U502
detector output level is switched to maintain a constant
output level during wide or narrow signals. (See Fig.3)
3
(U502).
(See Fig.2)
MI XER
MCF
RF AMP
BPF
Q506
XF500,XF501
Q506
VFO
1s t Local OSC
(PLL)
LV
Tuning vol tage
U206
VCO
PLL
MPU
AF PA AMP
U200
AQUA
U203B
AF AMP
19.200MHz
Fig.2
DJ-100
IF AMP
Q509
.
U205
SP
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