Tektronix 492 Operator's Handbook

SWEEPING THE DISPLAY
Horizontal
sweep for
the
display is
either
internal or
from an external sweep source . Sweep rate and source are
selected
by the
TIME / DIV
switch .
When the
TIME
/ DIV
switch is in the AUTO position , the sweep rate is
controlled by an internal microcomputer .
When the TIME / DIV is in the EXT position , a signal
source of
to +10
volts ,
applied to
the EXT
IN
HORIZ / TRIG connector , will sweep the crt beam the full
10
division graticule span
. The input
is dc
coupled ,
sensitivity is 1 V / div . External input impedance is about
10
ΚΩ .
The
beam can be
positioned by
the MANUAL SCAN
control when the TIME / DIV is in the MNL position ( see
Manual Scan of the Spectrum that follows ) .
MANUAL SCAN OF THE SPECTRUM
Manual scan is used to examine a particular point or
portion of a display such as one of the null points of a
frequency modulation spectrum or where a slow sweep of
the full span would take unnecessarily long . When the
3-6
TIME / DIV control is set in the MNL position , the display
may
be swept with
the
MANUAL SCAN control
. The sweep
scan
is
usually first
calibrated in
one of the timed
sweep
positions . Note that with a wide span / div and / or a narrow
resolution bandwidth setting , it is possible to scan too
rapidly to achieve an accurate display . Also , digital
storage
can
give
unpredictable
results
when
used with the
MNL SCAN mode . Digital storage is updated only when
scanning
toward
the
right .
REFERENCE LEVEL , RF ATTENUATION ,
AND
VERTICAL
DISPLAY
A
change
in the
REFERENCE
LEVEL
control requests
the
microcomputer to
change
the
display
reference
level the absolute amplitude represented by the top of
the
crt
graticule . The
microcomputer selects
the gain
distribution
( IF
gain and
input RF
attenuation
) for
the new
reference level
according to
the setting of
the FINE ,
VERTICAL
DISPLAY mode
, MIN RF
ATTEN
dB ,
and MIN
NOISE / MIN DISTORTION selectors .
The amount of attenuation between the RF INPUT and
the first mixer , set by the microcomputer , is based on the
reference level requested and the mode of the MIN RF
492
Operator's
Handbook
@

Tektronix 492 Specifications

General

Brand	Tektronix
Model	492
Category	Measuring Instruments
Language	English