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Threshold - the need for alignment can be controlled by setting the amount by which a possible
image can rise above the noise floor. This can be set between 0dB and 12dB, higher values
reduce the need for alignment.
Normal (Manual) can be used if occasional interruption of the sweep is unacceptable. When the
instrument calculates that alignment is needed (as defined by the Threshold setting) a message
is displayed and the Manual Align key or Status hard key can be used to initiate the alignment.
D.C. Sweep Modes DC (data comparison) sweep modes provide a different balance between
sweep speed, image rejection and noise floor from the normal modes. They have the potential
to provide total image rejection combined with reduced general spurii. No alignment is required.
Disadvantages include slower sweep for narrow spans at narrow RBWs, and vulnerability to
image rejection loss for specific signal spacings and for rapidly changing signal levels.
D.C. Mode 1 provides perfect image rejection for constant level signals provided that there are
no signals spaced at 40MHz +/-(2xRBW) apart. Sweep speed reduction for narrow spans is
moderate.
D.C. Mode 2 retains rejection unless signals exist simultaneously at both 32MHz +/-(2xRBW)
and 40MHz +/-(2xRBW) apart. Sweep speed reduction is slightly greater than for Mode 1.
Signal images and image rejection ratio are explained in the full instruction manual.
4.4.7 Sweep/BW > Detector Type
This menu enables the type of signal detector used to be changed.
Default (Positive) by default the analyzer uses a Positive Peak detector. This gives
the most accurate results in the majority of situations.
Set Detector creates a pop-up menu that enables alternatives to positive peak to be
selected. These are Negative Peak, Alternate Peak, Sample, Linear Average, Log
Average or RMS.
Detector types are further explained in the full instruction manual.
4.5 Level/Limits
4.5.1 Level/Limits > Units/Graticule
Enables the level to be shown in either dBm or in dB microvolts. It also enables the
brightness of the graticule to be controlled.
dBm selects level measurement in dBm (decibels relative to 1mW into 50
Ohms). dBuV selects level measurement in dB micro volts.
Note that the measurement unit applies to both the graticule values and
to the marker level readout.
Graticule creates a pop-up menu enabling the graticule to be dimmed, set to levels
only (horizontal lines only) or turned off completely.
4.5.2 Level/Limits > Reference Level
Enables the reference measurement level to be changed via attenuators and gain
stages. The key markings change depending upon the measurement units that
have been chosen. The figure indicates the level in dBm or dBuV represented by the
top of the graticule.The choice is:
Units/
Graticule
dBm
dBuV
Graticule
Ref
Level
+20dBm
(127dBuV)
0dBm
(107dBuV)
-20dBm
(87dBuV)
-40dBm
(67dBuV)
Detector
Type
Default
(Postive)
Set
Detector