Kenwood NXR-800 User Manual

NXR-800
10
TX Mod
19.2MHz
PLL circuit
IC307
5V #2
5V #1
19.2MHz
Q211
CF201
5V #1
4.5MHz
Q212
5V #1
Q213
5V #1
TX main
PLL circuit
4.5MHz
IC202
DDS IC
ATT ATT
Fig. 4 Transmitter DDS circuit
2-5. Transmitter main PLL circuit
The transmitter main PLL circuit consists of the VCO
(Q102 and Q103), PLL IC (IC101), IC102, Q104 and Q106
and produces the transmitter frequency signal.
The VCO Q102 produces transmitter frequencies from
368.000MHz to 383.995MHz.
The VCO Q103 produces transmitter frequencies from
384.000MHz to 400.000MHz.
The signal produced by the VCO (Q102 or Q103) is fed
to the buffer amplifi er and is amplifi ed by Q106. The higher
harmonic wave is attenuated by LPF and returns to the PLL
IC (IC101).
IC101 divides the VCO oscillating frequency signal and
transmitter PLL reference signal (4.5MHz), and compares
the phase with the 100kHz comparison frequency.
The phase difference signal produced by the comparing
phase is converted to a DC voltage by a lag-lead type loop
fi lter.
The DC signal is applied to varicaps D101, D102, D107,
and D108 to lock the VCO oscillator frequency with the de-
sired oscillator frequency.
At the same time, the DC signal passes through the
IC102 operational amplifier for monitoring the transmitter
main PLL lock voltage.
The output from the VCO passes through the buffer am-
plifi er Q104 and is supplied to the drive circuit.
Fig. 5 Transmitter main PLL circuit
2-4. Transmitter DDS circuit
The transmitter DDS circuit produces the transmitter
main PLL reference frequency signal 4.5MHz.
This circuit consists of IC307, IC202, CF201, Q210,
Q211, Q212 and Q213.
The 19.2MHz signal from the transmitter modulation
19.2MHz PLL circuit is amplifi ed by IC307 and supplied to
the IC202 reference signal pin.
IC202 produces the transmitter main PLL 4.5MHz refer-
ence frequency signal based on 19.2MHz on signal.
The spurious output by IC202 is attenuated by CF201
and LPF, 4.5MHz reference frequency signal is amplifi ed by
Q211, Q212, and Q213, and fed to the transmitter main PLL.
The comparison frequency of the transmitter main PLL is
100kHz and the PLL frequency step is 100kHz.
However, minute frequency step such as 2.5kHz and
3.125kHz because the DDS output frequency is variable.
CIRCUIT DESCRIPTION
Q106
TX DDS
circuit
1/R
1/N
PD
Fref.=4.5MHz
R=45
Fpd=100kHz
5V #2
Q104Q102
9V’ 9V’
5V #2
5V #2
368~
383.995MHz
368~
400MHz
IC102
OP-AMP
49
6
4.5MHz
IC101
PLL IC
CVT
Driver
circuit
D108
D107D101
Q103
9V’
384~
308MHz
D102
ATT
ATT

Kenwood NXR-800 Specifications

General

Brand	Kenwood
Model	NXR-800
Category	Repeater
Language	English