The W8IO Antenna Site - 4NEC2 and TANT

(updated 21 October 2016)

TANT is a DOS program written by Sinisa, YT1NT. It computes a Far Field table output from a text file which contains the simulated beam antenna radiation pattern.  The radiation pattern file can be produced by either EZNEC or 4NEC2.  The TANT instruction manual goes into great detail regarding the use of EZNEC to generate this text file, but does not mention 4NEC2.  Here are specific instructions on how to use 4NEC2 with TANT. Please refer to the TANT V1.2 User Manual and Appendix for additional information on the use of TANT.
4NEC2 is a Windows program written by Arie Voors.  It combines an excellent GUI with the universal-standard NEC2 software.  Version 5.8.9 and later incorporates the means to export text files which are compatible with TANT.  If you haven't already done so, please make sure that you have the latest version of 4NEC2.  
As of this date, the latest version is 5.8.11.

Step 1:  Build your beam model in 4NEC2 such that
    X-axis = element position on the boom
    Y-axis = element length
The maximum gain of the beam must occur at elevation = 0 and azimuth = 0  (Theta = 90, Phi = 0).  This means that the antenna or antenna array is modeled in Free Space.

Step 2. Change the 4NEC2 settings

Under "Settings", select phi/azim unit = Azim(ccw_x)/EL.  The Theta and Phi settings will not work.  You can always reset this after export.
If you wish to set the pattern resolution to 1 degree, under Settings>Memory Usage>Max Nr of field-points, change this number to 140,000 or larger.

Step 3.  Calculate the pattern

Select CALCULATE > NEC Output Data
Select "Far Field Pattern", "Full", Frequency (e.g. 144.1), Resolution (1, 2 or 3) degrees
Press "Generate"

Step 4. Create the text file for TANT

In the Pattern Window, select "FFtab" > "Azimuth/Phi slices"
Save the text file in the standard 8x3 (DOS) format  (e.g. antenna1.txt) in the same folder as TANT.exe.

If you are using Windows XP, then running TANT is fairly straightforward.  Go to Accessories (under Programs) and select the Command Prompt (C:/).  This will get you to a DOS window with the C: prompt.  Change directories (folders) to the folder which contains TANT.exe.  (I'm not going to explain how to use DOS - this is up to you!)  Type in "tant", then press "Enter".   You should now see the Tant user instruction screen.  Press any key to continue.  

Press "1", then type in the file name which you previously created in 4NEC2. Press "Enter".  

Press "2" to set the Tsky.  For 144 MHz, use 200.  For 222 MHz, use 70.  For 432 MHz, use 20.

Press "3" to set the Tearth.  For 144 MHz, use 1000.  For 222 MHz, use 600.  For 432 MHz, use 350.

Press "4" to compute your output.  In DOSBox, press CTRL-F12 to speed up the calculations. The 30 degree line will be highlighted in Red.  This is what Lionel, VE7BQH, uses in his G/T tables. These tables contain the G/T of 4-bay arrays of popular long-boom yagi beams.

If you do not have Windows XP available to use (e.g. you are using Windows Vista, 7, 8 or 10), you will need to download and install DOSBox.  This software emulates the DOS CPU and allows old programs to run normally).  After installation, type "Mount C C:\tant" <enter> if you created a folder called Tant in the root directory.  Then type "C:" <enter> and "tant" <enter>.


Comments are welcome!

contact Roger: email to 

rgcox2 (at) gmail.com

Roger Cox - Spring Lake, MI