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REFLECTOMETER (TV & CATV): Reflectometer test is executed on TV and CATV distribution
systems. Connecting the meter in pair with a calibrated noise generator on the cable to be
tested, if the distribution is perfectly matched, the graph will show only the calibrated noise
generated.
Conversely, if there is any mismatch in the distribution (i.e. shorted cable, open or cut cable),
causing the impedance not to be 75Ω in one or more points, this will result in stationary waves
being generated, represented by negative peaks (going down to 0dB) in the graph.
The parameters to be set to perform the measurements are the following:
“CABLE”, that can be: coax with FOAM dielectric; coax with COMPACT dielectric or coax with
AIRSPACE dielectric. To each cable type corresponds the V.o.P. index (Velocity of
Propagation) expressed in percentage from 1 to 99% that can be set in the MENU & ?
contextual menu, once the cable type has been selected (set this value using a known test
cable, varying the value until the displayed “Distance” equals the length of the test cable).
“VERT.POS” which represents the RF level reference, from 60 to 130dBµV
“dB/DIV” which can be set from 1 to 10dB/div depending on the signal strength and peaks
measurement.
“SPAN”, exactly as for a standard spectrum analysis can be set from 1 to 500MHz or above
(VHF, UHF, FULL) to focus the measurement on the desired portion of the TV band.
Moving the markers to two consecutive negative peaks will give the user the exact distance
between these two reflections, thus identifying the position of the leakage in the distribution
system.
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