Fig. 6-36. Typical Video Filter integrated display of 200 MHz RF
division signal amplitude on the Type 491. Note the dBm
3 3 . Check Signal Amplitude at the TO
reading of the Signal Generator attenuator dial, Increase
RECORDER Connector
the variable output attenuation of the Signal Generator
a. Equipment setup is given in step 29.
50 dB. Adjust the GAIN control for a 8 division display.
b. Set the VERTICAL DISPLAY switch to the LIN position,
c. Check-Range of GAIN control must equal or exceed
adjust the Signal Generator output and the Type 491 GAIN
50 dB.
control for a signal amplitude of 6 divisions.
NOTE
c. Connect a 1 probe from the test oscilloscope to the
TO RECORDER connector on the back panel. Terminate the
If the IF GAIN control does not meet this require-
connector into a 600 W Ioad by connecting a 600 W resistor
ment, perform step 36 then recheck.
from the TO RECORDER lack to ground.
d. Check--Signal amplitude should equal or exceed 24
mV (≥4 mV division of displayed signal amplitude).
32. Check INTENSIFIER Control Range
a. Test equipment setup is given in step 29.
34. Check Video Filter Operation
b. Change the DISPERSION selector to 100 kHz/div.
Uncouple the RESOLUTION control and turn the control fully
a.
Equipment setup is given in step 33.
clockwise (maximum resolution bandwidth).
b. With the DISPERSION selector at 100 kHz/DIV and
c. Set the VERTICAL DISPLAY switch to LOG position than
the TIME/DIV at 5 ms, uncouple the RESOLUTION control
adjust the GAIN control and the Signal Generator output
and turn counterclockwise one position from the full clock-
for a signal amplitude of approximately 8 divisions.
wise position.
c. Turn the VIDEO FILTER switch ON.
d. Turn the INTENSIFIER control to the OFF position (fully
C C W). Set the INTENSIFIER control for a display of nominal
d. Check--The display should resemble Fig. 6-36.
brightness. Set the CONTRAST adjustment to midrange.
e. Decrease the TIME/DIV to .5 s position and check the
e. Turn the INTENSIFIER control fully C W. The intensified
display. There should be no appreciable change in the
portion of the signal should measure between 3.5 and 4.5
display, when the FILTER is switched ON or OFF, unless there
major divisions.
is noise in the display. Set the FILTER to the OFF position.
6-34
