USER’S MANUAL__________________________________________________________________
134 _________________________________________________________________ M211322EN-D
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 ±20 µsec; 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 35 MHz, then
choosing fifteen subintervals might be a good choice. The hunt procedure
would then be able to get within 2.3 MHz 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 RVP900 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, for example, 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,
To Next Page
Loading...