Type 491
FINE RF CENTER FREQ
Centered
PHASE LOCK Controls
Display of nominal
INTENSITY
INT REF FREQ
OFF
brightness
Test Oscilloscope
Adjusted for optimum
FOCUS
and
ASTIGMATISM
display definition
Time/Cm
1 ms
OFF
INTENSIFIER
Volts/Cm
.5
As desired
SCALE ILLUM
Input Coupling
AC
Adjusted for a
POSITION (Horizontal
and
o
horizontally centered
21. Adjust MHz/DIV Dispersion and
Vertical)
sweep on the graticule
Linearity
baseline
20 ms
NOTE
TIME/DIV
CAL
VARIABLE
Dispersion accuracy is a measure of the frequency
TRIGGER
dispersion error within 8 divisions of a 10 division
SLOPE
+
display. It is measured by positioning the 1st fre-
Triggered sweep
LEVEL
quency marker on the 1st graticule line, then not-
LINE
SOURCE
ing the dispersion error as the distance the 9th
MHz/DIV
DISPERSION RANGE
marker is displaced from the 9th graticule line.
10 MHz/div
DISPERSION-COUPLED
See Fig. 6-20.
RESOLUTION
Linearity error is the measured distance any mark-
Midrange
DISPERSION CAL
er is displaced from its respective graticule line
Midrange
DISPERSION BAL
when compared over an 8 major division display.
All switches in off position
IF ATTENUATOR dB
See Fig. 6-21.
Midrange (000)
IF CENTER FREQ
Dispersion accuracy and the display linearity are
OFF
VIDEO FILTER
affected by the RF output amplitude, circuit con-
LIN
VERTICAL DISPLAY
stants, etc. DISPERSION CAL adjustment R208 pri-
Midrange
GAIN
marily affects the dispersion accuracy and C358
ON
POWER
the linearity. If these two adjustments will not
MIXER PEAKING
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