ADInstruments S7200 Operation Manual page 274

AD INSTRUMENTS S7200 TV Signal Analyzer Operation Manual
a quiet line inserter should be installed behind each modulator to be tested. The
advantage of using a quiet line inserter is that prior to inserting a quiet line, it
removes the line to be used for insertion of the quiet line first. Using this method,
making C/CTB measurements are "almost" undetectable by the end user
customer, where a low level audible sound will be heard, but this is an acceptable
trade-off to removing modulation completely, where the TV picture and sound
will completely shut down for the duration of the test. When performing a C/CTB
measurement with a quiet line inserter, (removing the line first) by
removing/inserting only one of the 2 video fields, the audible distortion coming
out of the speaker of your television is almost un-distinguishable. (if both fields
are used, the pitch of the audible distortion is higher, hence, more easily
distinguishable to the human ear).
TV Baseband Signal
Line Signal Remove Device
IF
Video
out in out in
RF Video IF Sound IF Video
out in out
in out
in
Analog TV modulator
To combiner
Figure 7-14 CTB quit line removing equipment connection
Quiet line inserter in this example: TVMS4200.
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