If you have a moderate understanding of antennas, you can use antenna modeling software to better understand how your antenna creations work.
When you build your own antenna system, you have two ways to estimate its performance. First, you can just use it and gather empirical data on its performance. For example, rotating a Yagi beam will give you a pretty good idea of its front to back performance. Or, you can compare an antenna with others and measure the results.
Second, you can use antenna modeling software to estimate what performance should be under ideal conditions. You will find two excellent antenna CAD programs available at no cost. These are MMANA-GAL Basic and 4NEC2.
Recently, I wrote about using MMANA to model the performance of my end fire active loop array on AM broadcast band. By changing the phasing between the two loops I was able to create very useful cardioid directional patterns in opposing directions. While my basic version of MMANA has some limitations, it has plenty of power to model most antennas, even phased arrays.
This week, I installed the free 4NEC2 software to model the same antenna. I was pleasantly surprised by the colorful 3D visualization you can see above. One each side of the picture are the actual loop models – one meter diameter loops at 2 meters above ground, spaced 30 meters apart on the E-W axis. You can see the out of phase signal sources in the lower segment of each loop.
The resulting radiation patterns demonstrates gain in the westerly direction at reasonable elevation angles. You can also spot the very sharp attenuation to the east.
Antenna Modeling Software – How It Works
Most antenna modeling software use some version of Numerical Electromagnetic Code. NEC started out as a mainframe program in the 1970’s where you designed your antenna system using Hollerith (hole punch) cards. In fact, you can still see the card paradigm maintained in the modern Windows versions of the product.
When run, NEC stimulates equations of electrical and magnetic fields along conductors and into free space. Your typical antenna model may contain dozens or hundreds of wire segments and millions of calculations. All of these take place after you design your antenna on a three-dimensional workspace by connecting wires together, and adding sources and loads to the elements.
Using NEC antenna modeling software is well within your reach if you have a moderate level of understanding about antennas, grounds and patterns. Have fun!