Azimuth Elevation Calculator
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SeaTel DAC 2202 Antenna Menu

Antenna Menu | AZ: Azimuth | EL: Elevation | REL: Relative Azimuth | POL: Pol Angle | Save Parameters |
The Antenna or AZ-EL menu shows the direction that the antenna is pointing and the AGC or signal level received. This is the screen most commonly viewed while troubleshooting or controling the antenna manually.

The azimuth and elevation can be driven manually from this screen using the up and down arrows for elevation, and the left and right arrows for azimuth. This is useful for manually searching for a satellite while watching for an increase in AGC.

One can also drill down into the menu by pressing the ENTER button and enter the Azimuth, Elevation or Relative settings manually. 

The pol angle can also be manually adjusted in this menu if the polang type is set to manual (0009) in the setup menu.
Press ENTER from the main Antenna menu to go into the Azimuth menu. Only the Azimuth will be displayed in the top left corner and the AGC in the bottom left corner.

The azimuth is the horizontal direction of the satellite, or the direction of the antenna, in a clockwise direction from from true north. Azimuth includes the relative azimuth (angle from the bow) and the ships heading. 

Press the left arrow to enter edit mode so that the cursor appears below the digits.

Use the left and right arrows and up and down arrows to change the azimuth to the required setting, and then press enter to command the new azimuth.

The commands from the DAC to the antenna to change elevation or azimuth can be viewed flashing in the bottom left corner of this screen. The direction each number represents is similar to the layout of a telephone dialpad (2=UP, 8 =DOWN, 4=LEFT, 6=RIGHT). The numbers only appear when the DAC requires the azimuth or elevation to change in a certain direction, to peak the signal, for instance.

Pressing NEXT at any time, will return to the main Antenna menu.
Press ENTER again to move to the Elevation screen.  Only the elevation and AGC will be displayed.

Elevation is the angle of the antenna, or the satellite, in a vertical direction above the horizon.

To change to a specific elevation, use the left arrow to enter edit mode. Use the left and right arrows and up and down arrows to change the digits to the required elevation and ENTER to target the new elevation.

Pressing NEXT at any time will return to the main Antenna menu.
The REL or relative azimuth is the horizontal angle from the bow of the vessel. The relative azimuth plus the heading of the vessel combine to give the true azimuth.

On unlimited azimuth antennas the REL goes from 000 on the bow, clockwise through 360 degrees.

On limited azimuth antennas, like to SeaTel XX04 series, the relative azimuth rotates through almost two revolutions through 680 degrees, begining at 020 off the starboard bow, rotating clockwise to 360 degrees on the bow and continuing for a second rotation to 700 degees off the port bow before unwrapping. (see drawing)

In some cases the antenna may not be may not be mounted with 360 or 000 on the bow, due to mounting or access restrictions. With dual TV antennas, one antenna is usually mounted with REL 360 facing the stern, so that both antennas are not in unwrap mode at the same time.

With VSAT antennas the homeflag magnet can be rotated to set the homeflag on the bow. A homeflag offset can also be entered (so that the antenna knows the REL of the bow) or an azimuth trim can be entered. Neither method will actually change the REL reading, but they will compensate for the offset.

To change the REL on this screen use the left arrow to edit mode, edit the digits and press ENTER. This has the same effect as moving the azimuth but it does not include the heading.
From the REL menu press ENTER to access the POL menu.

The POL menu displays the current angle of the feed in whole degrees. This angle is a direct feedback from the polang pot. The POL display is independent of pol offset or skew settings and only changes when the feed physically moves. 

The Pol cannot be changed in this screen when the polang type is set to auto (0072). To change POL manually you need to set the polang type to manual (0009) in the setup menu. To adjust the POL use the left arrow to edit mode, and then use the up and down arrow to change the POL one click at a time or holding the button to rotate. It does not seem to make any difference which digit the cursor is under, the feed still moves at the same speed. Press enter after each adjustment and let the feed settle. This is best done is small increments. 

In manual mode one should be able to drive the feed through 180 degrees from about 0040 to 0222 which are the software limits. Some of the latest models can drive the feed lower to about 0023. 

With Polang Type in the setup menu set to AUTO (0072), the feed will automatically rotate to the correct angle for the targeted satellite. 

If the polang pot in the antenna is correctly aligned, the feed should be square (orthogonal) with the antenna when the POL reading in this screen reads about 130 for a VSAT and 120 for a TV antenna. This is the center of travel of the potentiometer. The easiest way to check this is to target an imaginary satellite at the ships own longitude, and inspect the feed to check that it is indeed at 90 or 180 degrees.
Parameters must saved to NVRAM after changes are made, otherwise the changes will be lost when the DAC is reset. 

To save parameters, briefly press the left and right arrows together until SAVE NEW PARAMETERS is displayed. Press the left  arrow again to edit mode, and ENTER.

PARAMETERS SAVED will be displayed. Press NEXT to return to the main menus.