Dual markers provide an on-screen readout of
frequency and level including difference values.
The markers can be set to specified frequency
values, scrolled across the screen, or set to automatically find peaks.
A peak tracking mode is also provided which will
track the highest peak in the sweep despite changing frequency.
Marker amplitude readout can be in graticule units (dBm
or dBuV) or in linear units (mV or uW).