Blanking Variation And Sync Variation - Tektronix VM700T User Manual

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Bar Top. The Bar Top level is the average of 12 consecutive sample values,
centered midway between the approximate 50% points of the leading and trailing
edges of the bar. This measurement is always expressed as % Carr and is not
made unless Zero Carrier is selected as an amplitude reference in the appropriate
Measurement Location file, and it is found on the designated line. Note that the
default setting does not use Zero Carrier as a reference.
Blanking Level. Blanking level is calculated as a function of the Peak Carrier and
Zero Carrier pulse amplitudes, which are determined with the method discussed
previously under Peak Carrier and Zero Carrier Pulse topic. Then,
Zero Carrier pulse amplitude
% Blanking Level =
x 100
Peak Carrier amplitude
This measurement is always expressed as % Carr and is not made unless Zero
Carrier is selected as an amplitude reference in the appropriate Measurement
Location file, and it is found on the designated line. Note that the default setting
does not use Zero Carrier as a reference.
Bar Amplitude. Bar amplitude is measured from blanking level to the center of
the Bar Top level (NTC-7, Section 3.2). The blanking level is the average of 12
consecutive samples. If FCC Composite VITS, then these samples are centered
around the point that is 2.1 s before the measured 50% point of the bar leading
edge. If NTC-7 Composite VITS, then these samples are centered around the
point that is 10.9 s after the measured 50% point of the bar trailing edge. Bar
amplitude is reported in IRE.
Sync Amplitude. Sync amplitude is measured from blanking level to the center of
the horizontal sync tip pulse. The blanking level is the average of 16 consecutive
sample values, centered around the sample that is 6.55 s after the 50% point of
the leading edge of the sync pulse (nominal center of burst). The sync tip level is
the average of eight consecutive sample values, centered midway between the
50% points of the leading and trailing edges of the sync pulse. Sync amplitude is
reported in % Bar (when bar is present on this line) or as IRE (when bar is not
present).
Blanking Variation and
(FCC Rules and Regulations Part 73.682)
Sync Variation
Blanking Variation and Sync Variation measurement results are expressed as
both % Carr and IRE.
Parts of the sync tip and the back porch are acquired from 85 different active
video lines in field 1. The samples are acquired from every third line, starting at
field 1, line 10, and ending with field 1, line 262. The hardware low-pass filter is
used.
3–3
VM700T Video Measurement Set Option 01 NTSC Measurements