Tektronix 1760 series, User Manual

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Basic Measurements
1760 Series Component Waveform/Vector Monitor User Manual
4-10
Making SC/H Phase Measurements
(Option SC Only)
The
SC/H
display provides a vector display of the subcarrier-
to-horizontal-sync phase relationship. The burst vector and
the phase of the 50% point of the leading edge of sync are
displayed.
NTSC
Dual-Dot Display
When
REF
is set to internal, the 1760 has a dual-dot
SC/H
display (Figure 4-6). The dots represent the 50% points of
horizontal sync.
To make a measurement, align the burst vector as shown in
Figure 4-6. The location of the horizontal sync dot is the
SC/H
phase of the signal. With the dual dots,
SC/H
phase
range is limited to 180
°
, because the SC/H phase of a single
signal referenced to itself can only vary
±
90
°
. At 180
°
, the
video signal again has a + field subcarrier phase sequence,
making it “
SC/H
phased.”
Single-Dot Display
When
REF
is set to
EXT
, the 1760 has a single-dot display
(Figure 4-7). This relative mode allows the comparison of
two signals, the selected
INPUT
and
EXT REF.
The phase shift
between the two subcarriers can extend from 0
°
to 360
°
A dot near 0
°
(relative to burst) indicates the input is perfect-
ly SC/H-phased with the
EXT REF
input, and that the color
frames are properly matched. A phase reading of 180
°
indi-
cates that the
INPUT
and
EXT REF
color frames are not proper-
ly matched.