88 Chapter3
Making EDGE (with GSM) Measurements
Making the Spectrum (Frequency Domain) Measurement
ADC Range - Allows you to access the following selection menu
to define one of the following ADC ranging functions:
• Auto - Select this to set the ADC range automatically. For
most FFT spectrum measurements, the auto feature should
not be selected. An exception is when measuring a signal
which is “bursty”, in which case auto can maximize the time
domain dynamic range, if FFT results are less important to
you than time domain results.
• Auto Peak - Select this to set the ADC range automatically to
the peak signal level. Auto peak is a compromise that works
well for both CW and burst signals.
• AutoPeakLock - Select this to hold the ADC range
automatically at the peak signal level. Auto peak lock is more
stable than auto peak for CW signals, but should not be used
for “bursty” signals.
• Manual - Allows you to access the selection menu:
−6dB, 0dB,
+6 dB, +12 dB, +18 dB, +24 dB, to set the ADC range level. Also
note that manual ranging is best for CW signals.
Data Packing - Allows you to access the following selection
menu to define one of the following data packing methods:
• Auto - Data is automatically packed. This is the default setting
and most recommended.
• Short (16 bit) - Data is packed by every 16 bits.
•
Medium (24 bit) - Data is packed by every 24 bits.
•
Long (32 bit) - Data is packed by every 32 bits.
ADC Dither - Allows you to toggle the ADC dither function between
Auto, On, and Off. When set to auto (the default), ADC dither will
be activated when a narrow bandwidth is being measured, and
deactivated when a wide bandwidth is being measured. “ADC
dither” refers to the introduction of noise to the digitized steps of
the analog-to-digital converter; the result is an improvement in
amplitude accuracy. Use of the ADC dither, however, reduces
dynamic range by approximately 3 dB.
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