User's Manual

RVP8 User’s Manual
October 2005
TTY Nonvolatile Setups
3–30
Enable Burst Pulse Tracking: YES
This question enables the Burst Pulse Tracking algorithm that is described in Section
5.1.4. Remarkably, for such an intricate new feature, there are no additional
parameters to configure. The characteristic settling times for the burst are already
defined elsewhere in this menu, and the tracking algorithm uses dynamic thresholds
to control the feedback.
Enable Time/Freq hunt for missing burst: No
Number of frequency intervals to search: 5
Settling time for each frequency hop: 0.25 sec
Automatically hunt immediately after being reset: YES
Repeat auto hunt every: 60.00 sec
These questions configure the process of hunting for a missing burst pulse. The
trigger timing interval that is checked during Hunt Mode is always the maximum
+
20msec; hence no further setup questions are needed to define the hunting process in
time. The hunt in frequency is a different matter. The overall frequency range will
always be the full –100% to +100% AFC span; but the number of subintervals to
check must be specified, along with the STALO settling time after making each AFC
change. With the default values shown, AFC levels of –66%, –33%, 0%, +33%, and
+66% will be tried, with a one-quarter second wait time before checking for a valid
burst at each AFC setting.
You should choose the number of AFC intervals so that the hunt procedure can
deduce an initial AFC level that is within a few megaHertz of the correct value. The
normal AFC loop will then take over from there to keep the radar in tune. For
example, if your radar drifts considerably in frequency so that the AFC range had to
be as large as 35MHz, then choosing fifteen subintervals might be a good choice.
The hunt procedure would then be able to get within 2.3MHz of the correct AFC
level. The settling time can usually be fairly short, unless you have a STALO that
wobbles for a while after making a frequency change. Note that hunting in frequency
is not allowed for Motor/Integrator AFC loops, and the two AFC questions will be
suppressed in that case.
The RVP8 can optionally begin hunting for a missing burst pulse immediately after
being reset, but before any activity has been detected from the host computer. This
might be useful in systems that both drift a lot and generally have their transmitter
On. However, this option is really included just as a work around; the correct way
for a burst pulse hunt to occur is via an explicit request from the host computer which
“knows” when the pulse really should be present. Blindly hunting in the absence of
that knowledge can not be done because there are many reasons why the burst pulse
may legitimately be missing, e.g., during a radar calibration.
The automatic hunt for the burst pulse will always run at least once whenever the
feature is enabled. The automatic hunting ceases, however, as soon as any activity is
detected from the host computer. Only use this feature on radars with a serious drift
problem in their burst pulse timing.
Simulate burst pulse samples: NO
The RVP8 can simulate a one microsecond envelope of burst samples. This is useful
only as a testing and teaching aid, and should never be used in an operational system.