
3-7
Sweep
Sweep is the most complete way to measure the frequency response
of your cable network. SAM 4040D offers Sweepless
Sweep tool
to maximize the productivity of your troubleshooting time.
Sweepless
Sweep can be used to gain sweep information even
when there is no sweep transmitter available. See Chapter 4 for a
complete description of SAM 4040D’s sweep capability.
Sweepless
Sweep allows a technician to get sweep information
even if no transmitter is available. If a transmitter is ‘down’, or if
something is blocking the telemetry channel, Sweepless
Sweep
can still be used. In Sweepless
Sweep, a SAM 4040D unit
measures the stable carrier levels and memorizes them. These
levels can then be compared with the levels of the same carriers at a
different point in the network, and differences in frequency response
can be highlighted.
Proof-of-Performance Measurement Tools
SAM 4040D provides an extensive suite of tools for troubleshooting
and for performing proof-of-performance tests. Carrier-to-noise, hum
and depth of modulation are all calculated on analog video channels
in-service
and
in-channel. This allows technicians to measure the
performance customers really experience, all without any service
interruption. See Chapter 6 for more details.
•
Carrier-to-noise is measured using an advanced ‘quiet line’
algorithm. The SAM 4040D meter searches for a line of video
with no active signal (this typically happens on one or more lines
during vertical sync of an analog video channel). This allows the
noise measurement to be made in the middle of the channel
rather than in an unused side band. Thus, the reading reflects
what the CATV subscriber sees on the picture.
•
Hum is also measured in-service using DSP algorithms. Pre-
programmed filters help isolate power supply problems to 1-
times power-frequency, 2-times power-frequency, or all low
frequency components.
•
Depth-of-modulation can be measured in-service. This display
also allows the user to listen to either AM or FM audio carriers to
help identify a signal or troubleshoot some problems. If a steady