Atec JDSU-DSM-6300 - Manual (Page 7)

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DSAM-6300 DigitAl Service AnAlySiS Meter
Sweepless Sweep® Mode
For fundamental forward-distribution network alignment, the Sweepless Sweep
mode provides an economical solution. This mode scans the entire forward spec-
trum, displaying all levels across all frequencies (as defined by meter configuration).
Technicians can adjust the reception of the node amplifier with this scan and then
normalize the display by saving a reference. The resultant display is a flat zero-level
trace. When the measurement point is moved to the output of the RF amplifier, any
changes due to the amplifier will show as deviations (deltas) from the reference dis-
play. Because the cable network is designed on the unity gain principle, the same
reference is used as technicians test downstream amplifiers to compensate for the
effects of each cable segment. To isolate the effects of headend changes in levels, or
to align portions of the spectrum where there are no active carriers to reference, the
forward sweep option should be considered.
Forward Sweep Option
The Forward Sweep option continuously references existing carriers to ensure an
accurate measurement result. The DSAM-6300 offers a fast forward sweep espe-
cially in systems with numerous digital channels. By referencing 64, 128, and 256
QAM signal types, the DSAM-6300 removes any worries about subscriber interfer-
ence because there is no need to inject sweep carriers in the guard bands. Referencing
active carriers, instead of transmitting sweep signals over active carriers, lets the
DSAM-6300 sweep without degrading service quality.
The SDA-5500 headend transceiver inserts sweep points in unoccupied spectrum
to test frequency response. To remove the effects of headend level drift, the instru-
ment monitors levels and transmits new reference information with every sweep.
This means that if signal levels change in the headend, they will not affect the sweep
response measurement.
Reverse Sweep Option
Because the return path can be problematic, it should be tended to at least as often as
the forward path; and, any impairments should promptly be fixed. One of the best
procedures for preserving a clean return path is to establish an active reverse-sweep
maintenance plan. A reverse sweep can uncover mismatch problems, revealed as
standing waves, or diplex filter roll-offs that can severely degrade the quality of ser-
vices carried in the reverse band. The DSAM-6300 built-in reverse sweep transmitter
eliminates the need for a separate, cumbersome carrier generator.
Headend Sweep Equipment
With the DSAM-6300, one person can perform forward- and reverse-path align-
ment simultaneously. For reverse testing with more than one field technician, the
rack-mounted SDA-5510 Headend Reverse Sweep Manager can perform reverse
sweep on the same cluster of nodes for up to 10 different technicians. The SDA-5500
transceiver used in conjunction with the SDA-5510 receiver provides a full forward-
and reverse-sweep alignment solution. The SDA-5510 can also stand alone in remote
hub sites for dedicated reverse-alignment applications.
Sweepless Sweep provides a quick method to
check cable system integrity using active channels
to sweep the forward path. Sweep points do not
need to be added and no forward-path headend
gear is required.
Forward sweep uses a unique referencing
method to accurately reveal any problems in the
system without interfering with any of the analog
or digital carriers.
Tight reverse sweep points in the sweep plan dis-
play the entire return path with better resolution
and help to find mismatches or other problems in
the upstream transmission path.