Upstream Spectrum measurement mode views and analyzes ingress and distortion
on the upstream path (return path). It identifies the frequency at which
ingress occurs and displays the level value. This level measurement can
be checked in relation to a user-configured limit to determine a pass
or fail status. Test results can be stored for later reference.
The graph continuously updates as each frequency is measured. This forms
a wavy measurement line (trace) across the entire frequency range. When
excessive ingress noise occurs at a specific frequency, the measurement
line develops a peak on the graph.
The frequency range in this mode is 4-45MHz (North America) or 4-65MHz
(International), with the start and stop frequencies indicated on the
horizontal bar at the bottom of the screen. As you move the marker (the
thin vertical bar) across the frequency range with the left or right arrow
key, the numeric frequency and level value is displayed below the graph.
Use the up and down arrow keys to adjust the reference level from -70
to +65 dBmV in 1dB increments.
Softkeys
Three softkeys on the SPECTRUM screen provide the following options:
FILE
Save a completed test. You also can open an existing Upstream Spectrum
measurement file to compare previously collected data. Use the arrow keys
to choose the menu item you prefer and press ENTER to make your
selection.
VIEW
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 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 10MHz span.
Select (or deselect) Peak Hold to turn on and off the Peak Hold
function, which persists the highest level trace at each frequency for
improved noise isolation.
Select (or deselect) Reset to manually reset the Peak Hold function.
Select Field View to display the Field View measurement mode.
Select Pause to suspend measurement updates (Keystroke shortcut:
SHIFT 8). Use the arrow keys to choose the menu item you prefer and press
ENTER to make your selection.
LIMITS
Select the set of measurement limits you prefer - Tap, Ground
Block, TV, Cable Modem, or Off. Or select Edit
to access the CONFIGURE MEASURE - LIMIT SETS configuration screen, where
you can edit limit-set parameters to meet your needs. Use the arrow keys
to choose the menu item you prefer and press ENTER to make your
selection. NOTE: When you select Edit, the limit-set parameters
you define will remain constant in all channel plans and measurement modes.