REVERSE SWEEP (Optional Purchase
Required)
With reverse sweep, DSAM performs both as an active transceiver and as
an analysis receiver. 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. The measured results are returned to
the field DSAM over forward telemetry for comparison with the local DSAM
measurements. Only a single field user at a time can perform reverse sweep
with the SDA-5500. Larger networks typically will 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.
The reverse sweep plan, like the forward sweep plan, is configured in
the SDA headend/hub units and communicated to the DSAM field unit over
forward telemetry.
With reverse sweep 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 a single field user at a time
can perform reverse sweep with the SDA-5500. Larger networks typically
will 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.
Sweeping the reverse path is a little different from sweeping the forward
path. The lower reverse frequencies are not attenuated in cable as much
as the higher forward frequencies. In sweeping the forward path, the amplifier
is aligned so the amplifier compensates for the cable before it, i.e.
the cable segment between test point (the output of the amp) and the next
amp down the network. Sweeping the reverse path, the amplifier is aligned
so the response at the headend is within certain limits set by engineering.
The amplifier is aligned to compensate for loss characteristics in the
cable between the test point (input to amp) and the next amp closest to
the headend.
The following topics explain the user functions available within the Reverse
Sweep mode.
Softkeys
Four softkeys on the REVERSE SWEEP screen provide the following options
(same as FORWARD SWEEP screen):
FILE
Save Reference...
Saves the current measurement as a reference file.
Save File...
Saves the current measurement as a static measurement file. NOTE:
When a saved static measurement file is opened, the graph will be one
similar to the live measurement graph.
TIP: To assure exact measurement recording of current display, always
pause (SHIFT 8) measurement updates before saving or printing a measurement
file.
Load Reference...
Proceeds to a work folder associated with reverse sweep reference files.
Select a desired reference file. If the file selected is not compatible
with the current received sweep plan, a message will alert the user. NOTE: This feature allows you to display
the difference of the live data and the data stored in the file.
When a reference file has been chosen for display, the name of the reference
file appears in the subtitle bar in place of 'REF: NONE'.
The maximum length of the file name is 12 characters. When an additional
file is saved, the file name field in the "save a file" display
will contain the last label saved. This label may be appended, altered,
cleared or simply saved unchanged. If saved unchanged, an "overwrite?"
warning will be displayed that must be acknowledged.
NOTE: Since a reference file is essentially an average of the data
obtained from four previous sweeps, enough traces need to accumulate before
a file can be saved and used as a reference file. Thus, when the forward
sweep screen is accessed for the first time, the subtitle bar initially
displays a cross in place of the reference file name. Once enough traces
have accumulated "REF: NONE" or the current reference file
label is displayed.
Load File...
Loads a file as a static measurement file.
Clear Reference
Removes reference file from measurement and returns the subtitle bar to
"REF: NONE".
VIEW
Several viewing options are available to assist you with data assessment.
Press the VIEW softkey. Use the
arrow keys to choose the menu item you prefer and press ENTER
to make your selection.
Use the arrow keys to select Marker A
or Marker B as the active marker,
then press ENTER. Use the Left and Right
Arrows to move the marker.
Select Auto Reference to automatically
view measurement results in the best reference setting on the graph (Keystroke
shortcut: SHIFT 9). NOTE: For
best reference setting results you may have to select the Auto
Reference button more than once (up to three times).
Select 1 dB/div, 2 dB/div, 5 dB/div, or
10 dB/div to adjust the vertical resolution of the graph for the
best viewing.
Select (or deselect) Zoom to turn
on and off graph magnification. When selected, the Zoom feature produces
a display that has a frequency span that is defined by the position of
the markers in the original non-zoomed view.
Select Pause to suspend measurement
updates (Keystroke shortcut: SHIFT 8).
FORWARD or REVERSE
The third softkey toggles (changes) between FORWARD and REVERSE sweep modes.
Press this soft key to select the opposite direction sweep mode than what
you are currently viewing. If you are testing on directional test points
in the system, you will need both ports 1 and 2 on DSAM connected to the
test points to easily shift back and forth between the two modes.
SETTINGS
Test Point Comp...
Proceeds to the test point compensation configuration screen.
Changes are made and stored within the DSAM Configuration mode.
Telemetry Frequency...
Proceeds to the telemetry frequency screen.
Changes are made and saved within the active channel plan (label viewed
in upper right-hand corner of display).
Sweep Tilt and Limit ...
Proceeds to the sweep settings screen.
Changes are made and stored within the DSAM Configuration mode.