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21128026 R001 DSAM Help User Guide.book Page 272 Thursday, February 5, 2009 2:02 PM
Chapter 11 Measure Mode – Sweep Tab
Sweep Measurement Modes
Sweep Measurement Modes
Forward Sweep
Reverse Sweep
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The DSAM Sweep measurement displays the difference (delta) in
level from the headend to the field DSAM or vice versa. The main goal
is to measure the frequency response of the cable system distribution
network. This is done by injecting active sweep points (momentary
narrow test carriers) over a range of frequencies at the input of the
system. The level of each sweep point is measured at both the input
and the output of the system. At the receiving end (output) the two
values are compared and the difference is displayed on the DSAM,
thereby emphasizing any deviation caused by the network.
As an alternative to active test sweep points injected around a
channel, the actual broadcast video carrier can be used as a reference
carrier for that frequency. An optimized sweep plan includes both
active sweep points (representing unused frequency bands within the
network's spectrum), as well as reference carriers. This exclusive
Stealth Sweep™ technology is patented by JDSU and minimizes any
possibility of service interference.
Both directions of the network can be swept. A forward sweep is
performed with a transceiver and measurement system in the
headend or hub site, such as the SDA-5500 Stealth Sweep Trans-
ceiver. It transmits and measures active sweep points as well as
measures reference carriers.
You can use multiple field DSAMs at the same time with a common
SDA-5500. Typically, the Headend Technician or Network Engineer is
responsible for an accurate forward sweep plan within the SDA-5500
transceiver.
Reverse sweep is similar to forward sweep except that only active
sweep points are transmitted and measured by the DSAM field meter
and the SDA-5500 receives and measures the sweep points at the
headend or hub site. Only one field user at a time can perform reverse
sweep with the SDA-5500. Larger networks typically use a SDA-5510
Stealth Reverse Sweep Manager to handle only reverse sweep for
multiple field users and configure the SDA-5500 for only forward
sweep requirements.
DSAM Help User Guide
Rev. 001
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