3 Spectrum Analyzer Mode
3.2 Swept SA Measurement
trace determined by the Marker Trace rules. However, if the selected marker was
Off, Marker Function Off had to be the selected function, and it remains so even
after the marker is thus turned on, although you may then change it.
Fixed marker functions
In the case of a Fixed marker, it is not possible to turn on or change a band function.
This is because a Fixed marker holds the value it had when it became fixed; the trace
it was on may keep on changing, so the function value, which depends on trace
data, could not be calculated on an ongoing basis.
It is possible to have a Marker Function on for a Fixed marker, in the case where a
function was already on when the marker became Fixed. In this case the function
value is retained in the marker. It is also possible to have a Marker Function on for a
Fixed marker in the case when the marker was off and was turned on as Fixed
because Delta was pressed to create a reference marker, in which case the marker
function, marker function width, Y Axis value and marker function result that the
Delta marker had when Delta was pressed are copied into the Fixed marker. If Delta
is pressed again, causing the fixed reference marker to move to the delta marker’s
position, the marker function, marker function width, Y Axis value and marker
function result that the Delta marker had when Delta was pressed are again copied
into the fixed reference marker.
If a Marker Function is on for a Fixed marker, the marker’s reported value is derived
by the function. Therefore, you cannot directly set the X or Y value of a Fixed marker
which has a marker function turned on. Indirect setting as detailed above or when a
Peak Search is performed is allowed, as the Fixed marker is always placed on a trace
and can derive its function value from the trace at the moment when it is placed.
Interval Markers
What is an interval marker?
The interval power marker measures the average power across some time interval in
zero span.
Interval Density is defined to be Interval Power divided by Bn. Bn is the noise
bandwidth of the RBW filter, as noted and used within the Band Power computation.
Offscreen Markers and Band Functions
If a Normal or Delta noise marker is so near to the left or right edge of the trace that
some of the band is off-screen, then it uses only that subset of the Band Width that
is on-trace.
Neither Band power nor Band density markers are defined if any part of the band is
off the screen (unless they are Fixed with a stored function value in them), except
that when the edges of the bandwidth are trivially off-screen, due to mathematical
Spectrum Analyzer Mode User's &Programmer's Reference 345
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