HP 8591C User Manual page 267

Test Descriptions
Carrier-to-Noise Ratio Test Description
Pressing CARRIER/NOISE can have different results depending on 2 keys in
the setup menu, GATING YES/NO and PAUSE YES/NO . GATING set to NO
and PAUSE set to YES are the best settings for initially becoming familiar
with carrier-to-noise test. GATING set to NO causes the carrier- to-noise
test to initially enter the first variation of the test as described above. At
this point you can observe the noise at the lower channel boundary. If
there is a composite second order product at the lower channel boundary,
the marker will move slightly above it. This noise value is the system noise
from the output of the headend to the point of measurement. It does not
include noise contributed by headend active components or converters. Thus
noise measured the lower channel boundary must be added to the noise
contributions of headend components and converters (if used).
To move from the non-gated to the gated test, press CONTINUE. Now,
depending on the setting of PAUSE (and option 107 being present) the
test will either stop with line 12 displayed, or move directly into the gated
C/N test. When PAUSE is set to YES, line 12 is displayed giving you the
opportunity to explore the vertical interval by changing the line and field
values. A different line from 12 can be selected. If PAUSE is set to NO, this
step is skipped unless the analyzer finds it cannot recognize a quiet line. It
begins looking for a quiet line on line 12, but if it finds line 12 to be not quiet,
it moves to line 10, searches both fields there and moves up through the lines
to 20 looking for a quiet line. Thus, when PAUSE is NO, it will still pause if it
cannot find a quiet line.
When GATING is set to YES, pressing CARRIER/NOISE results in bypassing
of variation 1. Then, if PAUSE is set to NO, the analyzer will move directly to
the gated test. It is intended that you will select this conEguration of GATING
and PAUSE after becoming familiar with the operation of the test.
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