Vaisala RVP900, User Manual, Page: 142 / 484

Major marks are small downward triangles that represent integer multiples of 5 MHz; minor
marks are in between and represent 1 MHz steps.
The power spectrum in the example is from a system with an intermediate frequency of
30MHz. The left edge of the plot begins at DC, and the graph is centered on the sixth major
tick, that is, 30 MHz.
Horizontal Line at the Top of the Plotting Area
The horizontal line at the top of the plotting area is marked with an upward pointing major
and minor tick to indicate the present value of the burst pulse frequency estimator.
The major tick is a triangle whose position along the horizontal axis corresponds directly to
the estimated frequency. It should always be positioned directly over the main lobe of
spectral power.
The minor tick gives finer scale resolution by indicating the fractional part of each 1 MHz
multiple.
It is helpful to read the minor tick relative to the 10 horizontal division lines visible on most
scopes. Motion of the minor tick is apparent even with very small changes in burst pulse
frequency; a change of just 5 KHz can easily be seen. This means that you can observe the
frequency drift of the magnetron in great detail, and watch the AFC behavior in real-time.
Horizontal line at the Top of the Display
The horizontal line at the top of the display (above the spectra plot) indicates the value of
the AFC control voltage.
The line contains an upward pointing major and minor tick, similar to the ones used to
represent the burst frequency estimate on the line below. However, the horizontal axis now
represents voltage rather than frequency, and the overall span is the complete range of the
AFC's digital-to-analog converter.
The major tick moves from the left edge to the right edge as the AFC varies from its
minimum to maximum value. The minor tick traverses the screen at 10 times this rate.
6.6.2
Ps
Subcommands
The Ps subcommands change the design of the matched FIR filter, help calibrate the AFC
loop, and alter the display format.
The list of subcommands is printed on the TTY:
RVP900 User Guide M211322EN-J
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