How Relative Gain From Antenna Patterns Are Applied in EDX

The EDX antenna pattern file format contains antenna pattern gain information for the horizontal (Azimuth) plane and one or more vertical (Elevation) planes.  The relative gain at a particular azimuth and elevation is then essentially the relative dB gain in each of the two planes added together. To read more about the specific EDX antenna pattern file format please review this article: https://edxwireless.atlassian.net/wiki/spaces/EWKB/pages/590053379

To understand how this is done we will start with a simple example of an antenna pattern file that contains information only for the Azimuth plane and the elevation plane at the 0 azimuth..  The antenna gains are entered in the pattern file either in relative field (>0.0) or dB.  Regardless of the units, the EDX program converts these values into dB and then normalizes them with respect to 0dB. Normalizing is the process of finding the maximum dB gain value in the file for that plane, converting it to 0 and then adjusting all other gain values accordingly.  For example, the azimuth information in an antenna pattern file contains the following listed values (second column).  The normalized values are shown in the third column.

Azimuth   File_gain  Normalized_gain
0                 13.0              0
45               10.0             -3
90                 8.0             -5
135              4.0             -9
180             -6.0            -19
225              4.0             -9
270              8.0            -5
315            10.0            -3

An example of an elevation plane is here:
Elevation   File_gain  Normalized_gain
4                 5.0                -8
2               10.0               -3
0               13.0                 0
-2             10.0                -3
-4               5.0                -8

Once the data for azimuth plane and all of the elevation planes have been normalized we simply determine the dB gain at the azimuth of interest (interpolating between known azimuth values as necessary) and the dB gain at the elevation angle (also interpolated) and add the two gains together.  In the above example pattern file, the gain at an azimuth of 45 degrees and an elevation of 4 degrees below the horizon would be -3dB plus -8dB or a relative gain of -11dB.  The program then adds this value to the transmitter's "Maximum ERP" value to get the ERP at that bearing and elevation.

If there is more than one Elevation plane (we call each of these planes a "slice" containing the +90 to -90 range of elevation angles at a particular azimuth) you will need to interpolate the elevation gains between two slices where the desired azimuth falls between the azimuth orientations of the two slices.  For example, a typical antenna pattern file has two "slices", one at 0 degrees azimuth and one at 180 degrees azimuth.  The vertical gain at an elevation at 90 degrees azimuth would be the average of the elevation gains found for that elevation angle in the two slices.