Creating/Correcting .ant Files
Radio Mobile Compatible antenna files (XXXXXX.ant) are text files.
Each line is a relative gain in dB, and are normally zero or negative values.
A complete antenna file should contain 720 rows.
The antenna gain is defined in your Coverage parameters, not in the antenna file.
The antenna gain entered in the Coverage is the maximum gain of the antenna. The values in antenna file are used to modify that value.
If the radio beam of a path does not correspond to the direction where the antenna is pointing, the program will use the values in the antenna file to calculate the correction needed.
The antenna file only contains values in the horizontal plane and vertical plane.
In the file, each plane has 360 values, the horizontal first, followed by the vertical.
If the link direction is outside those planes, the program will interpolate a value.
If the antenna pattern is complex, there is a chance that the interpolation can give erratic results when the beam is pointing away from the recorded values.
The values for the horizontal plane and vertical plane generate two curves that intersect at two places. In system, if the antenna azimuth is zero and the antenna elevation angle is zero, the antenna will point to the North. In that case, the horizontal plane would have all values at elevation angle zero and would start at azimuth zero, moving toward East, South, West, and back to North.
The vertical plane would start at the Zenith over your head and move down to the North, then under your feet, South, and back to the Zenith.
So, the horizontal curves and the vertical curves would intersect at two points: to the North and to the South, both at elevation angle zero. Those two points are at line 1 and line 181 for the horizontal pattern, and lines 451 and 631 for the vertical pattern. So, if line 1 is does not equal line 451 or line 181 does not equal line 631, then the file is not valid.
Creating Antenna Patterns using the 3D-360 degree plot accepting phased verticals spreadsheet
Instructions for use are included at the top of the spreadsheet, but are repeated here for reference purposes.
The sheet provides a chart display and also allows 0 dB values to be inserted if required in the Azimuth and Elevation data columns.
Actual Azimuth and Elevation gain data can be entered at 10° intervals by ignoring the 5° columns and leaving them blank. The 10° values will be interpolated.
Enter datasheet Azimuth gain data in the Green area with the plot being displayed on the Green chart. Make sure that you enter your actual antenna Azimuth gain at 0°.
Enter datasheet Elevation gain data in the Blue area with the plot being displayed on the Blue chart.
To save Full Azimuth and Elevation data use 'Ctrl+Q to copy the 'yellow + tan' data area to the clipboard.
Paste into Notepad, and save as ''your_name.ant', using 'All Files' option.
To generate an Omni Antenna Pattern, enter the same gain into all Green area cells - but if the Elevation plot has its maximum gain below 0°, make sure you enter the Elevation pattern 0° gain value as the Azimuth gain!
Check that your elevation data at 0° and 180° are the same value. If not, a full 360° Azimuth pattern will have to be entered to allow for this.
How to Correct Antenna Files
The first thing to check when adjusting values is whether or not the antenna has an electrical down tilt.
Adjusting antenna pattern can be performed using Notepad and a spreadsheet software:
- Make a backup copy of the antenna file.
- Open the antenna file with Notepad, select all text, and copy to the clipboard (CTRL-A and CTRL-C).
- Paste the clipboard contents to a column of an empty spreadsheet.
- Perform modifications to a destination column (Using spreadsheet simple math functions)
- Replace the Notepad contents by copying the destination column in the spreadsheet to the clipboard (as text, not as formula) and paste it back into Notepad.
- Save the corrected file.