7
Digital Services Activation Meter (DSAM)
www.jdsu.com/nse
Features
Signal Level Meter
The DSAM family performs extremely accurate JDSU digiCheck™
digital power level measurements, as well as traditional SLM test
functions for analog video and audio levels. Furthermore, the ability
to measure C/N on analog carriers comes standard. Also included are
MER and pre- and post-FEC BER as well as errored seconds/severely
errored seconds on 64/256 QAM carriers. These tests allow technicians
to verify the reception of digital services within margin and quality
specications. This includes deep interleave modulation (j=128, i=5)
on the DSAM-2000, -2300, -3300, and -6300. The DSAM can analyze
downstream carriers to a full 1 GHz.
On a digital channel, the level mode measures the signal level and MER, and
tracks the BER and errored seconds.
Miniscan and Full Scan Modes
With miniscan and full scan test modes, technicians can see high- and
low-frequency digital and analog signals, and with limits activated can
easily verify that there is adequate level headroom. In miniscan mode,
the DSAM can monitor up to 12 channels at a time. In full scan mode,
the DSAM can monitor the entire channel plan, up to 999 channels. The
display shows the scan results either as an easy-to-read bar graph or in
an informative table.
Miniscan measures signal strength of up to 12 channels simultaneously.
Tilt Mode
Tilt mode shows the forward channel level tilt at the low and high ends
of the frequency spectrum. The variances of the levels, displayed at the
bottom of the DSAM screen, provide a rough indicator of the degree
of amplitude versus frequency distortion. Based on these results,
technicians know which equalizer pad to select for optimum atness at
the end of the line.
Hum Analysis Mode
The hum analysis mode measures hum on non-scrambled
analog channels. Because the instrument is battery powered, the
measurement is independent of ground loops, isolating it from
the line (mains). Severe hum on an analog channel appears on a TV
as either single (60/50 Hz) or double (120/100 Hz) horizontal bars
across the video screen. The hum display indicates the composite
level of all frequency components below 1000 Hz as well as the
fundamental hum frequency. A frequency graph displays the lower
levels of adjacent frequencies as well as the fundamental. This display
is valuable in determining the hum source by displaying a telltale
signature of the hum generating source.
Digital Quality Index™
Unique to JDSU, DQI indicates the overall health of a QAM stream
and is helpful for tracking intermittent problems. It is an easy to
understand index rating from 0 to 10, with 10 being the highest
quality. The measurement’s highly sensitive advanced DQI algorithm
enables technicians to quickly and easily catch and isolate RF domain
problems that are aecting HDTV and HSD services. DQI also catches
errors that traditional measurements miss. The measurement results
appear on a 180 second historical graph, facilitating the identication
of intermittent problems.
DQI displays intermittent, short duration impairments missed by MER and BER
as well as steady state issues typically captured by MER and BER.
(10 Seiten)
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