RC4500 Antenna Controller Chapter 5 MODES – In Depth Descriptions
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RUN: RUNAWAY SLOP <0.0 – 10.0 DEG, 0.0=OFF>
The pol_runaway_slop_item specifies the amount of movement that may be sensed before a runaway
condition is declared when the antenna is not supposed to be moving.
The unit of measure of the entered value is in hundredths of a degree (0.01 deg). If the installation has
pulse-based sensing this value will indicate the number of pulses the system may see before declaring a
runaway.
If the entered value is too low, normal noise from the fundamental position sensor or slight movement due
to wind may trigger a runaway. If the value is too high, it may take a long time to generate a runaway.
Setting this value to 0.0 will disable the runaway sensing
FDB: FAST ANTI-REV DEADBAND <0-9999 MSEC>
SDB: SLOW ANTI-REV DEADBAND <0-9999 MSEC>
The pol_fast_deadband_msec and azim_slow_deadband_msec items are used for the anti-reversal
system. To understand the purpose of these parameters, it is necessary to consider how position counts
are accumulated. The feedback from the azimuth and elevation position sensors is pulses. When a pulse
is received, the controller checks to see which way the antenna was last commanded to move. If the
antenna is moving, or last moved, counterclockwise, the polarization position count is decremented. If the
antenna is moving, or last moved, clockwise, the polarization position count is incremented.
In MANUAL mode, the user can jog the antenna. If the “POL CW” key is depressed, the antenna will
move polarization clockwise. If the user suddenly depresses the “POL CCW” key and the antenna drive
signals were instantaneously reversed, the antenna continues to move polarization clockwise for some
small period of time, then the antenna reverses direction and starts to move polarization counterclockwise.
This can cause position count errors. When the antenna drive signals are configured for counterclockwise
movement but the polarization is still moving clockwise, pulses which are received would cause the
polarization position count to decrement when the count should really be incremented because the
polarization is really still moving clockwise.
The anti-reversal system keeps the antenna axes from rapidly changing direction. If the polarization has
been moving in a given direction, the 'Deadband' CONFIG mode items specify the amount of time that the
system will wait before asserting the antenna drive lines to move the polarization in the opposite direction.
There are 2 different 'Deadband' values specified - there are unique fast and slow speed values. If the
polarization has been moving fast, the 'Fast Deadband' parameters specify the wait interval; if the antenna
has been moving slow, the 'Slow Deadband' parameters specify the wait interval. Both 'Deadband' values
are given in milliseconds.
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