User manual

Reference: Making Measurements
3–14
WFM 90 & WFM 91 User Manual
Differential Phase and Gain Measurement Box
Differential gain (dG) and differential phase (dϕ) measurements use
the graticule markings located at the outer edge of the B-Y or U axis
180° line. See Figure 3–6.
10
o
2°
dφ
dφ
Figure 3–6: Differential gain and phase measurement box
Making Vector Measurements
Chroma Bandwidth
The horizontal and vertical axes of the vector graticule contain
markings for checking chroma bandwidth. A subcarrier frequency
sine wave (whose amplitude places it on the outer compass rose) is
used as a reference. When the frequency is changed, the diameter of
the circle should reduce in size. At a point equal to 70.7% of full
amplitude (–3 dB), there are gaps in the horizontal and vertical axes.
This calibration aid makes it possible to check the –3 dB points of
the demodulator output amplifiers.