are peak detected; signals below the cursor are
averaged. The cursor should position anywhere within
the graticule window.
IDENTIFY 500 kHz/ONLY. When active, the vertical po
sition of the display alternately shifts about one division.
Spurious signals shift horizontally on the alternate sweep,
true signals do not shift. Reduce FREQ SPAN/DIV to
500 kHz with a signal tuned to center screen, reduce
TIME/DIV to a slow sweep rate, and press the IDENTIFY
button. Note the display of the calibrator signal.
PHASELOCK (Option 03). Activated to reduce residual
FM when narrow spans are selected. The button lights
when active; pressing the button turns phaselock off. When
active, the microcomputer automatically selects phaselock
for a span/division of 50 kHz or below in bands 1 through 3,
100 kHz or below in band 4, and 200 kHz or below in bands
5 and above.
Calibration—492/492P Service Vol. 1 (SN B030000 & up)
Performance Check
AUTO RESOLUTION. When activated, RESOLUTION
BANDWIDTH changes so bandwidth is compatible with
FREQ SPAN/DIV selection. Check by changing FREQ
SPAN/DIV and noting that RESOLUTION BANDWIDTH
changes. UNCAL indicator should not light over the FREQ
SPAN/DIV range if TIME/DIV selector is in AUTO position.
FREQUENCY SPAN/DIV. As this control is rotated
clockwise, FREQ SPAN/DIV should change from 0 to MAX
in 1-2-5 sequence. Display should indicate this change.
Range of the Span/Div depends on Options (see Specifica
tion section).
RESOLUTION BANDWIDTH. As this control is rotated,
resolution bandwidth should change in decade steps from
1 MHz to 1 kHz (100 Hz Option 03).
AF. When activated, center frequency readout initializes
to 0 MHz. The frequency difference, to a desired signal or
point on the display, can now be determined by tuning that
point to center screen and noting the readout. Check by
measuring the difference between calibrator markers. If the
frequency is tuned below "0 ” , the readout will indicate mi
nus (-).
DEGAUSS. When pressed, residual magnetism build-up
in the local oscillator system is reduced. Switch FREQ
SPAN/DIV to 1 MHz and tune the calibrator marker to cen
ter screen. Note the signal position, then press the
DEGAUSS button. The signal should shift horizontally and
then return to a new location. Press again and the signal
should return to the same new location. Return FREQ
SPAN/DIV to 100 MHz.
FREQUENCY RANGE. Two push buttons that shift the
492/492P frequency bands. Press the Δ button and note the
up shift of bands; then press the V button and note that the
bands shift down to the 0 to 4.2 GHz range (0 to 1.8 GHz
Option 01).
CAL. Checked when performing Turn On Procedure.
REFERENCE LEVEL. Continuous control that requests
the microcomputer to change the reference level one step
for each detent. In the 10 dB/DIV Vertical Display mode, the
steps are 10 dB. When FINE is activated, the steps are
1 dB. In the 2 dB/DIV mode, the steps are 1 dB or 0.25 dB
for the FINE mode. When FINE is activated in the 2 dB/DIV
mode, the ΔΑ mode is operational. The REFERENCE LEV
EL goes to 0.00 dB then steps in 0.25 dB increments from
an initial 0.00 dB reference level.
Set the MIN RF ATTEN to 0 dB. Set the vertical display
to 10 dB/DIV, and rotate the REFERENCE LEVEL control
counterclockwise to +30 dBm then clockwise to
— 120 dBm. Note the change in the display. Return the REF
LEVEL to -20 dBm and note that 10 dB of RF ATTEN is
switched in at —20 dBm.
MIN RF ATTEN. Sets the minimum amount of RF attenu
ation. Changing RF LEVEL will not decrease RF attenuation
below that set by the MIN RF ATTEN selector.
FINE. When activated, REF LEVEL switches in 1 dB in
crements for 10 dB/DIV display mode, and 0.25 dB for
2 dB/DIV display mode. In the 2 dB/DIV display mode, FINE
actuates ΔΑ mode.
MIN NOISE/MIN DISTORTION. One of two algorithms is
selected to control attenuator and IF gain. MIN NOISE (but
ton illuminated) reduces the noise level by reducing attenu
ation 10 dB and decreasing IF gain 10 dB. MIN
DISTORTION reduces IM distortion due to input mixer over
load. To observe any change, the RF ATTEN, displayed by
the crt readout, must be 10 dB higher than that set by the
MIN RF ATTEN selector.
UNCAL. This light comes on when the display is
uncalibrated. Set the TIME/DIV to 50 ms, deactivate the
AUTO RESOLUTION, and set the RESOLUTION
BANDWIDTH to 10 kHz. UNCAL should light and remain lit
until the FREQ SPAN/DIV is reduced to 200 kHz or the
RESOLUTION BANDWIDTH is increased to 1 MHz. Return
the TIME/DIV to AUTO and activate the AUTO RESOLU
TION. Set the FREQ SPAN/DIV to 100 MHz.
3-6
REV AUG 1981
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