To fully understand Downstream Spectrum measurement mode results, you
should be familiar with the Downstream Spectrum graph and the viewing
options available in the Downstream Spectrum mode.
Arrow Keys
You can use the left and right arrows to move the marker. With each non-continuous
key press, the marker increments or decrements to the next or previous
frequency point in the span. Use the up and down arrows to adjust the
graph for best viewing of the signal level measurements. NOTE:
Each arrow key press changes the reference setting by one (1) dB. The
reference level range is -100 to +60 dBmV.
Softkeys
Three softkeys on the DOWNSTREAM SPECTRUM screen provide the following
options:
FILE
Save a completed test. You also can open an existing Downstream 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 Upstream Spectrum to display the Upstream Spectrum measurement
mode.
Select Pause to suspend measurement updates (Keystroke shortcut:
SHIFT 8).
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.
Settings
Select Center Frequency to set the center frequency of the Downstream
Spectrum span. Set the center frequency between 40 MHz and 1000
MHz by using the numeric keypad and then press the ENTER key.