HP 54520 Series - Page 178

- horiz magnify -
(on
7° Windau
|
Math/FFT Menu
FFT Softkeys
More Softkey
The more softkey selects the second level of the math menu when the FFT
function is selected.
Horiz Magnify Softkey
The horizontal magnify softkey allows expansion of the frequency
record. Use the magnify off mode for viewing the entire FFT spectrum.
Use the magnify on mode for looking at two frequencies that are close
together and for making maximum accuracy measurements. When on is
selected, the center freq softkey is available for centering on the desired
frequency. The center freq softkey uses software expansion to center
the frequency record to the desired frequency.
The number of points displayed on the screen for FFT functions is always
500, When magnify is off, a compression algorithm is used to compress all of
the FFT points into 500 points. The algorithm accurately displays peaks and
most noise. However, low points in the noise are occasionally missed. When
magnify is on, the actual FFT points are displayed, 500 points at a time.
Freq Span Softkey
The frequency span softkey controls the span, the maximum frequency,
of the FFT record when the horizontal magnify softkey is set to off
Changing the span of the FFT record with a channel source causes the time
base setting to change. The span is the sample frequency divided by two.
Because the sample frequency for memories is fixed, once a record is stored,
the span is also fixed and cannot be changed.
The keypad does not have keys for entering MHz or kHz. But, the keypad does
have a key for enter exponents, Eex. For example, to set the span frequency to
125 kHz, press the following keys: 1, 2, 5, Eex, 3, Enter.
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