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Measurements
4–10
1780R-Series Operator’s Manual
The captured display remains on the screen even if the input signal is
removed. The display is lost when the DIFF GAIN menu is exited by
any method, including touching <GO TO DIFF PHASE>, pushing
any of the four front-panel menu buttons, pushing the front-panel
LINE SELECT button to enter Line Select mode, changing the
selected line if already in Line Select mode, or turning instrument
power off.
To exit Freeze mode, touch <FREEZE> again.
DIFF GAIN Measurement Information
The 1780R-Series provides two methods of making differential gain
measurements: single- and double-trace.
The single-trace method of differential gain measurement resembles
differential gain on the 520A-Series. This method requires the
operator to normalize the gains, but those settings will be stored and
recalled at next entry to DIFF GAIN mode. The amount of distortion
is read from the graticule scale.
The double-trace method of differential gain measurement resembles
double-trace differential phase in both 1780R-Series and R520A-Se-
ries. This method requires the operator to null the space between the
ends and individual steps of the two traces. This provides greater
accuracy than the single-trace method, and gives an on-screen
readout of the distortion measurement.
Single-Trace DIFF GAIN Measurement Procedure
1. Touch <SINGLE>.
2. Apply a staircase signal or a ramp signal with subcarrier to the
1780R-Series.
3. Use the vectorscope variable gain control to set the amplitude of
the chroma to be measured to the edge of the compass rose.
4. Use the large knob to set the phase of the chroma to be measured
to the nine o’clock position. See Figure 4–3.
5. Use the Waveform Vertical Position control to place the
beginning of the trace (waveform CRT) on a graticule reference
mark.
Measurements
4–10
1780R-Series Operator’s Manual
The captured display remains on the screen even if the input signal is
removed. The display is lost when the DIFF GAIN menu is exited by
any method, including touching <GO TO DIFF PHASE>, pushing
any of the four front-panel menu buttons, pushing the front-panel
LINE SELECT button to enter Line Select mode, changing the
selected line if already in Line Select mode, or turning instrument
power off.
To exit Freeze mode, touch <FREEZE> again.
DIFF GAIN Measurement Information
The 1780R-Series provides two methods of making differential gain
measurements: single- and double-trace.
The single-trace method of differential gain measurement resembles
differential gain on the 520A-Series. This method requires the
operator to normalize the gains, but those settings will be stored and
recalled at next entry to DIFF GAIN mode. The amount of distortion
is read from the graticule scale.
The double-trace method of differential gain measurement resembles
double-trace differential phase in both 1780R-Series and R520A-Se-
ries. This method requires the operator to null the space between the
ends and individual steps of the two traces. This provides greater
accuracy than the single-trace method, and gives an on-screen
readout of the distortion measurement.
Single-Trace DIFF GAIN Measurement Procedure
1. Touch <SINGLE>.
2. Apply a staircase signal or a ramp signal with subcarrier to the
1780R-Series.
3. Use the vectorscope variable gain control to set the amplitude of
the chroma to be measured to the edge of the compass rose.
4. Use the large knob to set the phase of the chroma to be measured
to the nine o’clock position. See Figure 4–3.
5. Use the Waveform Vertical Position control to place the
beginning of the trace (waveform CRT) on a graticule reference
mark.