3.6.0 OSCILLOSCOPE/
SPECfRUM
ANALYZER/ MODULATION SCOPE SECTION
•or.
•INAU
'0•!11
DVM
It
A~
I'
'I
l
FIGURE
3-4-CLOSE
UP OF SCOPE CONTROLS
3.6.1 INTENSITY
The intensity control varies the brightness
of
the
scope
trace.
3.6.2 FOCUS
The
focus co
ntr
ol varies the s
harpn
ess
of
the scope
tr
ace.
3.6.3 HORIZ
This seven position rotary switch selects the horizontal
sweep ra
te
or
the external horizontal sweep
input
when
the osci
ll
oscope
fu
nction
is
being used. On the R-2400,
this same
control
is
used to select the dispersions
of
I,
.1,
and
.01
MH
z/div
when the spectrum analyzer func-
tion is selected with the function switch. The sweep rate
is automatically fixed when in the spectrum analyzer
mode.
3.6.4 HORIZ VERNIER
This potentiometer controls the horizontal sweep rate
when the oscilloscope functions is b
ei
ng used.
The
calibrated
po
sition is
the
fully clockwise position. This
cont
ro
l is disabled when the R-2400 spectrum analyzer
function is being used.
3.6.5 SOURCE
Th
e source control
is
a
three
po
sition ro
tar
y switch which
selec
ts
the
s
our
ce for the scope vertical input. "
MOD
"
(modulation)
will
display
the
out
go
in
g
RF
modulation
signal
or
th
e recovered modulation signa
l.
Th
e
"EXT
AC"
(external A C) position
se
lects
AC
coupled ext
erna
l
input from the BNC
connecto
r.
The
"EXT
D
C'
' (exter-
nal DC) position
se
lects the
DC
coupl
ed
external input
from the same BNC connector.
3.6.6 VERT
A four position rotary switch controls the
verLical
dis-
play. Oscilloscope
operat
i
on
uses values marked to the
right
of
the switch indicating volts per division. Va
lu
es
marked to the left
of
the
switch are used when modula-
tion
is
displayed
on
the oscilloscope. The right bezel
of
the oscilloscope has a numerical scale corresponding
to
values
of
.25 kHz, 2.5 kHz
and
25
kHz
p
er
division.
This allows deviation measurements
to
be made even
when the service monitor
LCD
display is not selected to
"DEY
/OJoA
M" and gi
ves
the technician the ability to
detect non-symmetric modul
at
ion. This switch
is
dis-
abled when the R-2400 spectrum analyzer is being u
se
d.
3.6.7 VERT VERNIER
The vertical vernier potentiometer
contro
ls the vertical
inputs to the osc
ill
oscope. The calibrated position is
fully clockwise.
NOTE:
Th
e vertical vernier potentiometer is also func-
tional when the R-2400 spectrum analyzer mode is being
used. It is
imponant
to have this control in the
"Ca
l" posi-
tion to ensure true
IOdB
/ div vertical accuracy.
FIGURE
3-5-CLOSEUP
OF
SCOPE TRACE
3.6.8
POSITION
The
stacked concentric potentiometers control the ver-
tical
and
h
or
izontal positions
of
the scope trace.
For
R-2400 spectrum analyzer operation, these con-
trols are also used to center the observed spectrum.
When entering the spectrum analyzer mode, use the
''Vert
Po
sition" control (innermost control)
to
set the
base
of
the noise floor
at
the bottom graticuJe. The
Horiz
Po
sition control is adjusted by first programm-
ing for an RF frequency
of
000.0000 Mhz (de
r
ef
erence), then with the dispersion control set for
lMhz
/ div, use
the
Horiz
Po
sition control (oute
rmo
st
potentiometer) to cen
te
r the observed spectrum display
horizontally
aro
und
the
center (5th) vertical graticule.
3-8
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