Technical data

5-7
Operating Concepts
Sweep Types
• logarithmic frequency sweep
• list frequency sweep
Linear Frequency Sweep (Hz)
The LIN FREQ softkey activates a linear frequency sweep that is displayed on a standard graticule with ten
equal horizontal divisions. This is the preset default sweep type.
For a linear sweep, sweep time is combined with the channel's frequency span to compute a source sweep
rate:
sweep rate = (frequency span) / (sweep time)
Since the sweep time may be affected by various factors, the equation provided here is merely an
indication of the ideal (fastest) sweep rate. If the user-specified sweep time is greater than 15 ms times the
number of points, the sweep changes from a continuous ramp sweep to a stepped CW sweep. Also, for 10
Hz or 30 Hz IF bandwidths, the sweep is automatically converted to a stepped CW sweep.
Logarithmic Frequency Sweep (Hz)
The LOG FREQ softkey activates a logarithmic frequency sweep mode. The source is stepped in
logarithmic increments and the data is displayed on a logarithmic graticule. This is slower than a
continuous sweep with the same number of points, and the entered sweep time may therefore be changed
automatically. For frequency spans of less than two octaves, the sweep type automatically reverts to linear
sweep.
Stepped List Frequency Sweep (Hz)
The LIST FREQ [STEPPED] softkey activates a stepped list frequency sweep, one of two list frequency
sweep modes. The stepped list mode allows the analyzer to sweep a list of arbitrary frequency points. This
list is defined and modified using the edit list menu and the edit subsweep menu. Up to 30 frequency
subsweeps (called "segments") of several different types can be specified, for a maximum total of 1601
points.
One list is common to both channels. Once a frequency list has been defined and a measurement
calibration performed on the full frequency list, one or all of the frequency segments can be measured and
displayed without loss of calibration.
When the LIST FREQ [STEPPED], key is pressed, the analyzer sorts all the defined frequency segments
into CW points in order of increasing frequency. It then measures each point and displays a single trace
that is a composite of all data taken. If duplicate frequencies exist, the analyzer makes multiple
measurements on identical points to maintain the specified number of points for each subsweep. Since the
frequency points may not be distributed evenly across the display, the display resolution may be uneven,
and more compressed in some parts of the trace than in others. However, the stimulus and response
readings of the markers are always accurate. Because the list frequency sweep is a stepped CW sweep, the
sweep time is slower than for a continuous sweep with the same number of points.
Segment Menu
The LIST FREQ [STEPPED], softkey provides access to the segment menu, which allows you to select
any single segment (SINGLE SEG SWEEP,) in the frequency list or all of the segments (ALL SEGS
SWEEP,) in the frequency list. See the following information on how to enter or modify the list