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Setup – Home Flag Offset (IMA Software 1.04 or lesser) 5012-91 Installation Manual
8-1
Figure 8-1 Antenna stops In-line with Bow
8. Setup – Home Flag Offset (IMA Software 1.04 or lesser)
If you have IMA software version 1.05 or greater, please refer to the next chapter (Setup – Azimuth Trim.
In IMA software versions 1.04 and earlier Home Flag Offset is used to calibrate the relative azimuth value of the antenna to the
bow line of the ship. This assures that the encoder input increments/decrements from this initialization value so that the
encoder does not have to be precision aligned. When the antenna is pointed in-line with the bow (parallel to the bow) the
“Relative” display value should be 000.0 Relative (360.0 = 000.0). Good calibration is especially important if blockage mapping is
used, because the values entered into the AZ LIMIT parameters are entered in Relative Azimuth. The default Home Flag Offset
value saved in the ICU is 000.
The default mounting of the radome is with its bow reference
in-line with the bow and the base hatch in-line with the stern
(aft reference of the radome). There are valid reasons for
mounting the ADE in a different orientation than the default.
One of these would be that the hatch of radome needs to be
oriented inboard of the ship for safe entry into the dome (ie
ADE is mounted on the Port, or Starboard, edge of the ship and
safe entry is only available from inboard deck or inboard mast
rungs).
Observe initialization of the antenna. When Azimuth drives CW
and then stops at “Home” position, VISUALLY compare the
antennas pointing, while at Home position, to the bow-line of
the ship (parallel to the Bow).
If it appears to be very close to being parallel to the bow, you
will not need to change the HFO and should proceed with
Optimizing Targeting. When “Optimizing Targeting” small
variations (up to +/- 5.0 degrees) in Azimuth can be easily
corrected using the AZ TRIM feature.
If it is NOT close (stops before the bow or continues to drive
past the bow) Sea Tel recommends that HFO be adjusted to
calibrate the relative position of the antenna.
If the antenna is pointing to the LEFT of the bow line: If the antenna stops driving before the bow line, when targeting a
satellite it will fall short of the desired satellite by exactly the same number of degrees that it fell short of the bow line. You
must calibrate HFO using either of the methods below.
If the antenna is pointing to the RIGHT of the bow line: If the antenna continues to drive past the bow line, when targeting a
satellite it will overshoot the desired satellite by exactly the same number of degrees that it went past the bow line. You must
calibrate HFO using either of the methods below.
If you find that a large value of AZ TRIM parameter has been used to calibrate the antenna, This indicates that the Relative
position is incorrect and should be “calibrated” using the correct HFO value instead of an Azimuth Trim offset.
If the radome was purposely rotated, has a large value of AZ TRIM or was inaccurately installed (greater than +/- 5 degrees),
there are two ways of setting Home Flag to compensate for the mounting error. They are Electronic, or Mechanical, Calibration
of Relative Antenna Position (Home Flag Offset).
Above, you VISUALLY compared the antenna pointing, while at “Home” position, to the bow-line of the ship and found that the
antenna pointing was NOT close to being parallel to the bow-line. It stopped before the bow or went past the bow OR you
found AZ TRIM has been set to a large value, therefore, HFO needs to be adjusted.
Ascertain the exact amount of error using the appropriate procedure below, enter the HFO to calibrate the antenna to the ship,
save the value and re-initialize the antenna to begin using the new value.
8.1. You Found a Large AZ TRIM value:
If Targeting has been optimized by entering a large value of AZ TRIM; First, verify that you are able to repeatably
accurately target a desired satellite (/- 1.0 degrees). Then you can use the AZ TRIM value as the HFO value (so
you can set AZ TRIM to zero). Set Home Flag to the AZ Trim value that was calculated (and click SAVE) and then set
the AZ Trim value to zero (and click SAVE). Both AZ TRIM and Home Flag are entered as the number of degrees and
tenths of degrees.