7.3.1 Setup
The following setup parameters are available:
Center Frequency (MHz) and Frequency Span (MHz)
The two selections are independent of each other and made on two separate settings.
The center frequency selection sets the frequency of the center of the scale to the chosen value - normally
where the signal to be monitored would be located. In this way, the main signal is in the center of the display
and the frequencies on either side can be monitored.
The span selection is the extent of the frequency coverage that is to be viewed or monitored on the display. Any
custom values can be entered. The display may show the default values of 2.4, 4.8, 7.2, and 9.6 MHz (for
values of less than 9.6MHz), however, the screen displays two vertical purple lines representing the entered
span's frequency boundaries.
Start Frequency (MHz) and Stop Frequency (MHz)
The CX380C allows the entry of Start and Stop frequency in place of the CF and Span. The entry mode can be changed by
tapping on the CF or START icon. The entry range is from 5MHz to 1000MHz.
Zero Span
Zero Span mode is typically used for measuring the level variation of an analog channel. There are two ways to enter
the Zero Span mode:
Select CF of an analog channel and enter 0Hz for the frequency span, or
Select Start and Stop frequencies to be the same as the CF of an analog channel.
The display can be set for Linear or Log mode.
Vertical scale (dB)
Sets the logarithmic scale to 1, 2, 5, 7, or 10dB per division.
Resolution Bandwidth (kHz, MHz)
Selectable filter sizes (100 kHz, 300 kHz, 1000 kHz, 3000 kHz)
Resolution bandwidth is the bandwidth of the IF filter, which determines the selectivity of the spectrum analyzer. A
wide resolution bandwidth is required for wide sweeps, while a narrow filter is used for narrow sweeps.
The narrower the RBW setting, the better the frequency resolution; however, narrower filter settings require more
measurement time
Wider filters are used when the display needs to be updated rapidly, or when wide modulation bandwidths are to be
displayed.
Reference Level (dB)
To ensure that the input stages of the analyzer are not overloaded, an RF attenuator is used. If input stages are
overloaded, spurious signals may be generated within the instrument, resulting in possible false readings. However, if
too much attenuation is inserted, additional gain is required in the later stages (IF gain) and the background noise level
is increased, which can sometimes mask lower level signals. Thus, a careful choice of the relevant gain levels within
the spectrum analyzer is needed to obtain optimum performance. Select the appropriate Reference Level from 0 dB to
70 dB, in 10 dB increments.
Signal
Select the appropriate Signal type for your test:
Burst
: Best for burst signals such as Return Path UCD / OFDMA or detecting intermittent interference.
Digital
: Best for QAM and OFDM power measurements.
Analog
: Best for Analog Channel measurements.
The
Dwell/Average
setting selections are dependent on the
Signal Type.
.
Resolution
Low
: uses 120 data points
Medium
: uses 240 data points (recommended)
High
: uses 480 data points
Marker
There are 4 markers available -- two verticals and two horizontal. They can be activated by tapping the MARKER
function key.
Signal levels, frequencies and deltas are displayed with color coding.
To move a marker, tap on the Circle associated to each marker. For fine tuning of the marker, use Up, Down, Left, and
Right arrow keys.
Vertical and horizontal markers can be paired and be moved together.
Search
The Peak or Min or both in the measured span can be searched automatically. The search is updated per sweep.
CX380C User Manual RevA00
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