Kenwood NXR-800 User Manual

NXR-800
9
2-3. Transmitter modulation 19.2MHz PLL circuit
The transmitter modulation 19.2MHz PLL circuit produc-
es the reference frequency signal for the Transmitter DDS
circuit and modulates the low-frequency components.
The circuit consists of IC302, IC303, IC305, IC306, X301,
Q304, Q305, and Q307.
The signal generated by the VCXO (X301) is fed to the
buffer amplifi er Q307.
The VCXO (X301) signal enters buffer amplifier Q307
and is amplifi ed by Q305. The higher harmonic wave is at-
tenuated by the LPF and returns to IC303. Its phase is com-
pared with that of the reference frequency 5kHz.
The phase difference signal produced by the comparing
phase is converted to a DC voltage by a lag-lead type loop
fi lter. This DC voltage is input to the IC305 invert amplifi er
(B/2) and is synthesized with the modulating signal. This DC
voltage is input to the X301 control voltage terminal for con-
trolling the VCXO oscillating frequency 19.2MHz.
The DC voltage passes through the IC306 operational
amplifi er, and is output as a voltage signal (CVT-MOD) for
monitoring the modulating 19.2MHz PLL circuit lock voltage.
The 19.2MHz oscillating signal is fed to the Q307 buffer
amplifier and is amplified by Q304. The higher harmonic
wave is attenuated by the LPF, fed to IC307, and is used as
the reference frequency signal of the transmitter DDS circuit.
Q415
Internal
/External
Ref circuit
1/R
1/N
PD
Fref.=19.2MHz
R=1920
Fpd=10kHz
8V #2
Q417X401
8V #2
IC407
5V #3
Q416
5V #1
Q401
5V #2
Q412
5V #18V #2
5V #3
5V #3
19.2MHz
19.2MHz
IC401
OP-AMP
28
6
5.99MHz
or
10MHz
IC404
PLL IC
CVT-REF
TX Mod
19.2MHz
PLL circuit
RX unit
CN406
19.2MHz
Q402
5V #2
CN405
19.2MHz
Fig. 2 Transmitter reference 19.2MHz PLL circuit
Q305
TX Ref
19.2MHz
PLL circuit
1/R
1/N
PD
Fref.=19.2MHz
R=3840
Fpd=5kHz
8V #2
Q307X301
IC302
5V #2
IC305
5V #2 8V #2 8V #2
5V #2
5V #2
19.2MHz
IC306
OP-AMP
Q304
5V #2
28
6
19.2MHz
IC303
PLL IC
CVT-MOD
TX DDS
circuit
19.2MHz
Mod signal
Fig. 3 Transmitter modulation 19.2MHz PLL circuit
CIRCUIT DESCRIPTION

Kenwood NXR-800 Specifications

General

Brand	Kenwood
Model	NXR-800
Category	Repeater
Language	English