Burst Parameters
If the frequency of the transmit burst increases when the AFC control voltage increases,
type Yes. Otherwise type No.
When the following parameter is set correctly, a numerical increase in the AFC drive (D–
Units) results in an increase in the estimated burst frequency. If the AFC loop is completely
unstable, try reversing this parameter.
Burst frequency increases with increasing AFC voltage: NO
The following parameter enables the burst pulse tracking algorithm (see 7.2.4 Burst Pulse
Tracking (page 177)). The characteristic settling times for the burst are
defined elsewhere
in this menu, and the tracking algorithm uses dynamic thresholds to control the feedback.
Enable Burst Pulse Tracking: YES
The following parameters 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. No further setup parameters are needed to define the hunting process in
time.
• For the hunt in frequency, the overall frequency range is always be the full -100 ...
+100% AFC span.
The number of sub-intervals 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% are tried, with
a one–quarter second wait time before checking for a valid burst at each AFC setting.
Enable Time/ Freq hunt for missing burst: No Number of frequency intervals to
search: 5 Settling time for each frequency hop: 0.25 sec
Choose the number of AFC intervals so the hunt procedure can deduce an initial AFC level
that is within a few MHz of the correct value. The normal AFC loop then takes over 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 15 sub-intervals 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 are suppressed in that case.
Chapter 5 – TTY Non-volatile Setups
99
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