6. Check Saw Out Signal Amplitude
a. Requirement--SAW OUT signal amplitude is 70 to
100 kHz (fully cw)
b. Connect the test oscilloscope probe to the SAW OUT
connector on the rear panel of the Type 491. Adjust the
c. Measure the amplitude of the sawtooth waveform.
Must measure between 70 and 90 mV.
c. Adjust the GAIN control far a signal amplitude of
approximately 6 divisions.
7. Check External Triggering
d. Decrease the DISPERSION to 0, keeping the signal
centered on screen with the IF CENTER FREQ controls.
a. Requirement--Sweep circuit must trigger on an exter-
nally applied signal of 0.2 V within the frequency range of
e. Switch the SOURCE switch to INT position and adjust
20 Hz to 100 kHz.
the LEVEL control for a triggered display.
b. Apply the output of the Audio Signal Generator
f. Adjust the position control to position the 1st marker to
through a coaxial cable and T connector to the rear panel
the 1st graticule line (see Fig. 5-1), then check the sweep
TRIG IN connector. Monitor the applied signal with the test
timing for each position of the TIME/DIV selector. Marker
oscilloscope by connecting a coaxial cable between the T
input, TIME/DIV selector and type of display is listed in Table
connector and the oscilloscope vertical Input connector.
the output control for a signal amplitude of 0.2 V peak to
d. Change the Type 491 SOURCE switch to EXT position.
Adjust the LEVEL control and check for a triggered sweep
with the SLOPE switch in either the + or - positions. Must
trigger with a 20 Hz, 0.2 V externally applied signal.
e. Change the Signal Generator frequency to 100 kHz
and adjust the output control for a 0.2 volt peak to peak
f. Adjust the LEVEL control and check for a triggered
sweep with the SLOPE switch in either the + or - posi-
tions. Must trigger with a 100 kHz, 0.2 volt signal.
g. Remove the externally applied signal and T connector
from the Type 491 TRIG IN connector.
8. Check Line Triggering
a. Requirement-Sweep will trigger on LINE with the
LEVEL control centered and the SLOPE switch in either posi-
b. Set the SOURCE switch to LINE position.
c. Check for a triggered sweep with the LEVEL control
Fig. 5-1. Time markers aligned to check sweep timing.
centered and the SLOPE switch in either the + or - posi-
g. Return the TIME/DIV selector to 1 ms position, then
apply 10 ns and 5 ms markers to the Type 491.
9. Check Sweep Timing
h. Turn the VARIABLE control fully counterclockwise.
a. Requirement-Sweep timing accuracy must be within
3% of indicated TIME/DIV selector Position.
i. Check-A minimum of five (5 ms) markers should be
displayed within the 10 division graticule width. Variable
b. Apply 10 ns and 1 ms time markers from the Time-Mark
control range 2.5:1.
Generator through 40 dB attenuator to band A, RF INPUT
j. Return the VARIABLE control to the CAL position.
connector. Set the front panel controls as follows: