Tektronix 1730 Series, Инструкция по эксплуатации

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1730–Series Operating Instructions
2–22
100
80
60
40
20
–20
–40
NTSC
7.5
12.5%
0%
75%
100%
2% & 4% K FACTOR
Tek
Figure 2-16: NTSC graticule.
There are
$
2 IRE and
$
4 IRE markings at the center of the –40 IRE line (sync
tip) to assist in measuring sync amplitude. This scale is designed to be used with
the 2 line and 2 field sweep rates.
The scale on the right side of the graticule is for measuring depth of modulation.
The scale extends from 0% at the 120 IRE line to 100% at sync tip (–40 IRE
line).
The boxed area slightly to the right of center at the 100 IRE level is scaled in 2%
and 4% increments for precise tilt measurements. This structure is designed to
work with an 18
m
s half–amplitude duration (HAD), 2T bar. The set of solid and
short dashed lines to the left of the bar tilt measurement structure is used to
measure pulse–to–bar ratio; they are weighted to include K–Factor ratings of 2%
and 4%.
Making Measurements. To use the NTSC vertical scale to make line time
distortion and pulse–to–bar ratio measurements, set the signal blanking level at
the graticule blanking line (0 IRE) and position the leading edge of the Compos-
ite Test Signal bar to the ascending arrow (just right of graticule center). Check
to see if insertion gain is unity. If it is not, adjust the 1730–Series VAR for
exactly 100 IRE of signal amplitude from baseline to the middle of the white bar.
Check to see that the negative–going bar transition passes through the descend-
ing arrow.
To measure the K–Factor line time distortion, measure the largest deviation of
the bar top (tilt or rounding) within the structure. The structure is designed to
ignore the first and last 1
m
s of the bar where short–time distortions (ringing,
overshoot, undershoot, etc.) occur. The solid outer box equals a 4% K–Factor,
while the dashed line inner box equals a 2% K–Factor. (For signals with a bar