(a) Oscilloscope Type 561A is used with plug-in unit Type 3A72
Dual-Trace Amplifier for the vertical deflection, and plug-in Type 2B67 Time
Base for the horizontal deflection.
Connect all test equipment to the
circuit under test as indicated in figure 1-17.
(b) Set the FREQ control of oscillator #1 to 1,000 Hz, and the
AMPLITUDE control for an output of 0 dBm0 (normal signal level at the point
of measurement). Measure the received level at station B.
(c) Set the FREQ control of oscillator #2 to 1,000 Hz and adjust
the AMPLITUDE control for an output equal to the received level.
(d) Place the switch in position 2, feeding the oscillator #2
output to the vertical input of the oscilloscope. On the Time Base (figure
5 of IB 3321), set the SOURCE switch to EXT, and adjust the LEVEL control
for a stable display. Adjust the TIME/DIV controls so one cycle of the sine
Each division is then equal to 40.
waveform covers nine grid divisions.
With the POSITION control of the Type 3A72 plug-in, center the display on
(e) Place the test switch in position 1. This disconnects oscillator
#2 from the vertical input of the oscilloscope and in its place feeds the
received test signal to the vertical input.
However, the signal from
oscillator #2 continues to feed the horizontal input to the oscilloscope.
The pattern of the display should now be a straight line. Adjust the FREQ
control of oscillator #2 slightly until the oscilloscope waveform (straight
line) remains stationary. Phase jitter will cause smearing of the center of
the straight line where it crosses the graticle axis.
(f) Measure the amount of peak-to-peak phase jitter by measuring the
smearing length in grid divisions of the waveform's zero crossing on the
Divide the smearing length (grid division) by the total
length of a single cycle (nine grid divisions) on the horizontal axis and
multiply it by 360 as shown in the following formula: