RC4500 Antenna Controller Chapter 5 MODES – In Depth Descriptions
105
RUN: RUNAWAY SLOP <0.0-10.0 DEG, 0.0=OFF >
The elev_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 will disable the runaway sensing
FDB: FAST ANTI-REV DEADBAND <0-9999 MSEC>
SDB: SLOW ANTI-REV DEADBAND <0-9999 MSEC>
The elev_fast_deadband_msec and elev_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, east (down), the azimuth (elevation) position count is decremented. If
the antenna is moving, or last moved, west (up) the azimuth (elevation) position count is incremented.
In MANUAL mode, the user can jog the antenna. If the UP arrow key is depressed, the antenna will move
up. If the user suddenly depresses the DOWN arrow key and the antenna drive signals were
instantaneously reversed, the antenna continues to move up for some small period of time, then the
antenna reverses direction and starts to move down. This can cause position count errors. When the
antenna drive signals are configured for down movement but the antenna is still moving up, pulses which
are received would cause the elevation position count to decrement when the count should really be
incremented because the antenna is really still moving up.
The anti-reversal system keeps the antenna from rapidly changing direction. If the antenna 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 antenna in the opposite direction.
There are 2 different 'Deadband values specified - there are unique fast and slow speed values. If the
antenna 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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