QRAT ILLUM.
Inactive state, no graticule lights. Active
state, graticule lights.
BASELINE CLIP.
Inactive, no clipping of the display
baseline. Active, display intensity at the baseline is clipped
(subdued).
TRIGGERING.
Triggering mode is activated by pressing
one
of four push buttons. Pressing any one of the buttons
cancels
or deactivates the other mode.
FREE RUN.
Active, trace free runs.
INT.
Active, trace displayed when signal or noise level at
left edge is >2.0 divisions and risetime is faster than 24 ms
(15 Hz).
LINE.
Active, trace triggered at power line frequency.
EXT.
Active, trace runs when an external signal >1.0 V
peak or less is applied to the back panel EXT IN connector.
SINGLE SWEEP.
Pressing this button to activate single
sweep aborts the recurrent sweep; pressing the button
again arms the sweep generator and lights READY, which
remains lighted until the sweep completes. The analyzer
makes a single sweep of the selected spectrum when the
conditions determined by TRIGGERING are met. Single
sweep mode is cancelled when any TRIGGERING button is
pressed. The effect of SINGLE SWEEP may be more appar
ent if VIEW A, VIEW B, and B-SAVE A are off.
TIME/DIV.
Selects sweep rate and manual scan oper
ation. In MNL position, MANUAL SCAN control should vary
the crt beam across the full horizontal axis of the crt
graticule.
VERTICAL DISPLAY.
Display modes are activated by
three push buttons. Pressing any of these buttons cancels
the other mode.
10 dB/DIV.
Active, display is a calibrated
10 dB/division, 80 dB dynamic range. Calibration is
checked later in this procedure.
2 dB/DIV.
Active,
display
is
calibrated
2 dB/division, 16 dB dynamic range. Calibration is
checked later in this procedure.
LIN. Active, display is linear between the reference
level (top of graticule) and zero volt (bottom of graticule);
the crt VERT DISPLAY reads out in volts/division.
Calibration—492/492P Service Vol. 1 (SN B030000 & up)
Performance Check
PULSE STRETCHER.
Active, increases the fall time of
video signals to make narrow pulses on the display easier to
see. With FREQ SPAN/DIV at MAX, TIME/DIV.at 5 ms and
Digital Storage off, the markers should increase in bright
ness when PULSE STRETCHER is active.
VIDEO FILTER.
Two filters, independently selected to
provide WIDE (1/30th) or NARROW (1/300th) of the resolu
tion bandwidth for noise reduction.
DIGITAL STORAGE (Option
02). Either or both sections
of memory can be selected to provide digital storage. When
either or both are activated, signal amplitude should remain
constant. Vary the PEAK/AVERAGE control and note that
noise level below the PEAK/AVERAGE cursor is averaged.
VIEW A/VIEW B.
When SAVE A is off, either
VIEW A or VIEW B will display all data (1024 bits) in
memory. Both sections of memory are updated each
sweep. When SAVE A is activated, VIEW A displays
data saved in the A section of memory (512 bits) and
VIEW B displays data (512 bits) in the B section of mem
ory. B section is updated each sweep.
SAVE A.
Active, contents in A memory are saved
and not updated. Verify operation by changing REF LEV
EL and observe that the VIEW A display does not change
when VIEW B is inactive.
MAX HOLD.
Active, stores maximum signal ampli
tude at each memory location. Verify operation by chang
ing FREQUENCY or REF LEVEL and note that the
maximum level at each location is retained.
B-SAVE A.
Active, the difference between updat
ed data in B section of memory and that saved in A is
displayed. Verify by saving data in A, then changing the
refrence level and pressing B—SAVE A; only the differ
ence can be observed by cancelling VIEW A and VIEW B.
The reference (zero difference) level is normally set at
graticule center, but can be internally adjusted. See Ad
justment Procedure, step 15.
PEAK/AVERAGE.
When digital storage is activated
with VIEW A or VIEW B, this control positions a horizon
tal line or cursor on the display. Signals above the cursor
REV AUG 1981
3-5
