9.49 Antenna-Pointing

The Antenna-Pointing logical device is a 'high level' driver for motor driven antennas. It is used together with a driver for the type of antenna controller used.

While the plain driver for the antenna controller simply supports to set the azimuth/elevation/pol-offset parameters of the antenna, the Antenna-Pointing logical device extends this with additional capabilities:

• It permits to set the antenna pointing by supplying a satellite orbit position. The Antenna-Pointing logical device computes the antenna pointing from the satellite position and sends these values to the low level antenna driver.
• It maintains a list of satellite names, stored together with the orbit position of each satellite and the (manually fine tuned) antenna pointing values for each satellite. The standard user interface for the Antenna-Pointing logical device contains a comfortable tool to handle this list.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

• --- Contains the antenna pointing values, the selected satellite name and the orbit position of this satellite. You should use this page if you want to move the antenna to a certain orbit position.
• --- The list of satellite positions. You can select a satellite to move the antenna to with this page and you can maintain the satellite list.
• --- The device info page.
• --- The maintenance page. The configuration parameters described below are set at this page.

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameters which must be set to make the Antenna-Pointing device work properly.

Operation modes

The Antenna-Pointing device knows three different modes of operation. This is to adapt the behaviour of the device to different types of antennas. By setting the azId, elId, polId and orbitId configuration parameter or leaving them empty you select the proper mode of operation for a particular antenna:

• Normal 3-axis antenna : For this antenna type, set the azId, elId and polId configuration parameters to the appropriate parameter identifiers. Leave the orbitId setting empty.In this operation mode, the device will control all three axes of the antenna and it will store complete (az/el/pol) pointing vectors in the satellite table. Only with this operation mode the device is capable to perform orbit position to antenna pointing calculations.
• Polarmount type antenna : For this antenna type, only set the azId configuration setting. Leave the other message ID parameters empty.The device will use the azimuth angle to control the antenna's orbit arc setting. This value together with a orbit position angle gets stored in the satellite table.
• Intelligent mobile SNG antenna : The third mode of operation is used with car mobile SNG antenna controllers which accept a satellite orbit position angle to point the antenna to this satellite. To enable this mode, leave the azId, elId and polId configuration settings empty and set the orbitId parameter to the appropriate value.The device will act as a simple satellite name to orbit position translator in this mode. Only the orbit position gets stored in the satellite table, the orbit position will be commanded to the antenna controller when a satellite is selected.

Polarization plane handling

The Antenna-Pointing device accepts an operational parameter called 'rxpolplane' (H/V). This parameter may be used to select a certain receive polarization plane by turning the feed (This works with 3-axis antennas only.)

The device translates the commanded polarization angle when forwarding it to the antenna. If horizontal polarization is selected (which is the default if the parameter isn't used), the angle is forwarded as it is. With vertical polarization, the device either adds or subtracts 90 degrees before the value gets forwarded. The device decides if to add or to subtract based on the range of the polarization angle given by antenna controller driver.

If the configuration parameter polPlaneId is set, the device will forward the polarization plane setting to the given device / parameter rather than shifting the polarization angle. The destination may be a switch selecting the polarization plane or a comparable parameter of the antenna controller itself. This "pass-through" mode may be used with all types of antenna controllers, as long as there is a parameter to select the polarization plane.

Remarks

1. To make the antenna move to a satellite already stored in the list, double click to the satellite's entry in the - page.
2. Pressing the right mouse button on a satellite's entry in the list opens a context menu offering all funktions to manage the satellite list.
3. When entering a new satellite to the list, first move the antenna to it's calculated position by entering the satellite's orbit position at the - page. Optimize the antenna pointing. Then switch to the - page, add a new entry to the list and update this entry with the current antenna pointing.

Satellite position file

The Antenna-Pointing device stores the satellite positions in a text file in the base directory of the M&C/VLC software. It is named "XXXX.txt" where XXXX is the name of the Antenna-Pointing logical device. The file contains the satellite list as a table of semicolon separated fields. It may be imported by common spread sheet programs this way. The table columns are defined as follows.

1. satellite name
2. orbit position (deg. east)
3. antenna azimuth
4. antenna elevation
5. antenna polarization offset Be aware, that the numeric values are stored with a decimal dot (##.###), regardless of the default locale of your computer.

Variables defined by this device driver