JRC NDR-91 User Manual

5.2.1
lst Local
Oscillator
,
This
circuit
is single-loop
synthesizer
which
generates
the
signal
of
70.545
to
I
0O.4S4g
MHz
(
100
Hz
step)
corresponding
to the
receiving
frequency
from
90
kHz
to 29
.9999 MHz
and
provides
that
frequency
to
lst
mixer.
The
circuit consists
of
variable
divider,
phase
comparator
and VCO.
Furthermore
the
variable divider
is
composed
of
integer
part
and fraction.
For
frequency
data,
digits
of
lOMHz
to l00kHz
are
preset
in the
integer
part
and
digits
of l0kHz
to 100H2
in
the
fraction.
The reference
frequency
is
12.5
kHz
obtained
by dividing
the standard
signal
of
5 MHz
by
400.
The
phase
comparator
compares
the
phase
between
this reference
signal
and
variable divider
output
and
VCO
is
controlled
by the
DC
voltage
corresponding
to
that
phase
difference.
5.2.2
2nd
Local
Oscillator
This
circuit
feeds
the
signal
of
70 MHz
to the 2nd
mixer.
This
circuit is
composed
of
analogue
type
phase
comparator,
70
MHz
variable
crystal
oscillator
(VXO)
and
LPF.
These
are in the
phase-lock
loop
(PLL).
The
phase
comparator
compares
directly
the
phases
between
the
standard
signal
of
5 MHz
and
70 MHz,
and
the 70
MHz
variable
crystal
oscillator
is
controlled by
the DC
voltage
corresponding
to
that
phase
difference.
Usually
in PLL,
the
phases
are compared
between
5 MHz
obtained
by dividingT0
MHz
signal
by 14
atrd
the
standard
signal
of
5 MHz.
But in
this
circuit,
by
comparing
the
pulse
of
the
wavetbrm of
the 5 MHz
standard
signal
(the
pulse
width
is I
12
cycle of
70 MHz)
and
70
MHz
signal
every l4
cycles of
the waveform
of 70 MHz
signal,
the
phases
of
5 MHz
standard
signal
and 70 MHz
siganl
are directly
compared.
5.2.3 BFO
Circuit
This
circuit operates in
CIV,
SSB
or
AUX
mode,
and
provides
the
BFO
signal
to
the
productdetector.ThefiequencyoftheBFosignalcanbeadjustedbythe@
CLARIFIEE
knob.
In
case of CW mode,
the frequency
of
455
kHz
can
be varied
by more
than
+2kHz,in
SSB
mode,
the
frequency
of
456.5
kHz
can be varied
by
more
than
+50
Hz,
and in
AUX
mode
(option),
the frequency
of xxxx
kHz
can
be
varied
by more
than
150
Hz.
xxxx
rneans
456.7 in
FSK
mode and 45
6.9 in
FAX
mode.
This
circuit operates
as the clarifier
in
SSB
and AUX
modes.
5.3
PANEL
SECTION
The
panel
section is
composed of liequency
indicator
circuit,
mode
and bandwidth
indicator
circuit,
S
meter
and controls.
They
are mounted
on one
printed
circuit
board.
The
frequency
indicator
circuit consists
of 6-digit
numerical
LEDs for
the
receiving
frequency
set by ttre
I
rvtHZ
knob u"o
lTUlVe I
knob.
Since bandwidth
and mode selector
switches
are
non-locked
type, the
switch
information is
latched,
and according
to this
latched output,
LEDs
for
bandwidth
and mode
light
up. At
the
same
time, this
output
controls the
IF
filter
selector
circuit in
the receiving
section and BFO
selector circuit
in the local
signal
generator
section.
S meter indicates
the
AGC
voltage
when
the
-t7-
switch
on the front
panel
is
set to

JRC NDR-91 Specifications

General

Brand	JRC
Model	NDR-91
Category	Receiver
Language	English