User's Manual Part 2

Plot–Assisted Setups
RVP8 User’s Manual
April 2003
4–8
0.025 msec steps, and the uppercase commands shift in 1.000 msec
steps (approximately). The reason for shifting all six triggers at once
is that the relative timing among the triggers remains preserved.
However, the absolute timing (relative to range zero) will vary, and
this will cause the burst pulse A/D samples to move within the sample
window.
T/t The “T” command 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 The “Z” command 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”.
B/b These keys 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.
+ The “+” subcommand 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 can be found, then the previous trigger slew
and AFC are not changed.
4.4.3 TTY Information Lines Within “Pb”
The TTY information lines will resemble:
Zoom:x2, PlotSpan:5 usec, FIR:1.36 usec (49 Taps)
Freq:27.817 MHz, Pwr:–53.9 dBm, DC:0.14%, Trig#1:–5.00, BPT:0.00
Zoom Indicates the magnification (in amplitude) of the plotted samples. A
zoom level of “x1” means that a full scale A/D waveform exactly fills
the height of the sample window. Generally, the signal strength of the
burst pulse will not be quite this high. Thus, use larger zoom levels to
see the weaker samples more clearly. You may zoom in powers of two
up to x128.
PlotSpan Indicates the overall time span in microseconds of the complete scope
display, from left edge to right edge.
FIR Indicates the length of the impulse response of the matched FIR filter,
and hence, the duration of the burst pulse sample window. The length
is reported both as a number of taps, and as a time duration in
microseconds.
Freq Indicates the mean frequency of the burst, derived from a 4
th
order
correlation model. The control parameters for this model are set using
the “Mb” command (Section 3.3.6).