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SDA-5500/SDA-5510 Sweep Configuration: Sweep History and Theory

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Another difference between forward and reverse sweep alignment is that

signals in a reverse path plant are TDMA digital channels: multiple

transmitters are sending to one receiver at the headend. For these systems

to work, the reverse carriers must be turned off when not in use. Accordingly,

the sweep methodology that allows accurate forward path sweep without

injecting any signal cannot be used here. Sweep pulses must be injected.

To prevent any chance of system interference, Acterna recommends that

you not put any sweep pulses within active return path channels. However,

due to the narrow frequency pulse used by the Stealth system, the edges of

channels can almost always be used without creating any interference

problem. For example, if two return path telephony carriers are located at

21.0 to 21.6MHz, and 21.6 to 22.2MHz, sweep points can be injected

between and around the two channels at 21MHz, 21.6MHz, and 22.2MHz.

Because cable systems are designed with appropriate spacing for the

forward high frequency range, the reverse path may not require amplification

at each station. In the cable, lower frequencies are attenuated less than

higher frequencies.

Productivity Tools

Stealth sweep incorporates several productivity tools, described below, that

help you work more effectively.

Markers and Limits

• Stealth sweep systems incorporate several Marker and Limit functions.

• Vertical markers: Two vertical markers enable you to check frequency

and level at specified points on the sweep. The display also shows the

difference values. These vertical markers define the minimum and

maximum frequency range to measure.

• Horizontal markers: Two horizontal markers can be turned on or off.

When they are enabled, the horizontal markers show the maximum and

minimum response values on the sweep curve between the vertical

markers. Use these to automate maximum/minimum testing to find a

system’s flatness.

• Sweep limits: You can set a limit value for the largest deviation from

flat, and the meter will automatically display whether the current test

point passes or fails. Activate this by selecting the Limit Check mode

within sweep, and then setting the Limit Value (in dB).

• Sweep Limit Variable: A common formula for system flatness is “N/

10+X.” This means that the response at the Nth amplifier in the system

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