Table 35 Pb Subcommands
Command Description
I/i
Increments or decrements the length of the matched filter's impulse response. Each
keystroke raises or lowers the FIR length by one tap.
A/a & S/s
Raise/lower the aperture/start of the subwindow of burst pulse samples for AFC.
If you do not use these commands, the full FIR window is used.
Shortening the AFC interval results in two sample windows being drawn on the plot.
Position the smaller AFC window positioned in the center portion of the transmitted
pulse, where the burst amplitude and frequency are fairly stable.
L/l & R/r
Shift the group of RVP900 triggers left or right (earlier or later in time).
The lowercase commands shift in 0.025 μsec steps, and the uppercase commands shift
in 1.000 μsec steps (approximately).
The reason for shifting all 6 triggers at once is that the relative timing among the
triggers remains preserved. However, the absolute timing (relative to range zero) varies,
and this causes the burst pulse A/D samples to move within the sample window.
T/t
Increments or decrements the overall time span of the plot.
The available spans are 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000, and 5000
microseconds.
The value is reported on the TTY as PlotSpan.
Z/z
Zooms the amplitude of the burst pulse samples so that they can be seen more easily.
The value is reported on the TTY as Zoom.
> and <
The live plotted data can be logged to the $(IRIS_LOG)/rvp9–pb.log text file;
one line per plot.
%
Toggle between the IFDR IF-Input sources.
B/b
Temporarily disable or re-enable the burst pulse tracker.
The tracker must be disabled in order for the L/R keys to be used to shift the nominal
trigger timing.
The b key disables tracking and sets the trigger slew to zero; the B key re-enables
tracking starting from that zero value.
+
Initiates a hunt for the burst pulse.
Progress messages are printed as successive AFC values are tried, and the trigger slew
and AFC level are set according to where the pulse was found. If no burst pulse are
found, then the previous trigger slew and AFC are not changed.
6.5.3 TTY Information Lines In Pb
The TTY information lines resemble:
Zoom :x2, PlotSpan:5 usec, FIR:1.36 usec (49 Taps)
IF:Ch5(TXB) Freq:27.817 MHz, Pwr :–53.9 dBm, DC:0.14%,
Trig#1:–5.00, BPT:0.00
Chapter 6 – Plot-assisted Setups
135
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