Adding Radials to the Inverted L

An inverted L works against a ground circuit. You COULD put up the antenna and just pound a rod into the ground to complete the circuit, but for most of us, bare ground is a pretty poor conductor. We add a ground radial system in order to provide a good return path and minimize ground losses.

Ground losses reduce the efficiency of our antenna, in other words, power is lost to heating in the ground part of the antenna circuit. We have a problem here though. The antenna we’re modeling actually has buried radials (there are some pieces above ground, but the bulk consists of below ground wires. OOPS … NEC2 doesn’t handle wires below the surface of the ground.

NEC4 can handle buried radials and computer the results from using them properly, but NEC4 costs around $1000 to be licensed to use it, not including the front end for it. That takes it out of the range for most of us, so how can we come up with an acceptable model? Simple, we add another approximation! We’ll start with a very simple radial pattern and then experiment with it to see how sensitive our results are to changes in the radial pattern. If, for example, we change the number of radials or their length or their conductivity and we get no change in measurable parameters of the antenna, then we can be pretty sure that our model is ‘good enough’ to use.

FIRST … I added a simple radial pattern to see it’s effect. In this case, I modeled 8 50-foot wires spaced evenly around the feed point



Here is the wires table …


This is the 3D and elevation pattern which results

As you can see, results are approximately what we saw before. In the next post, we’ll take some time to look at actually creating the radials in the software.

NOTE: If you cannot read the figures, you should be able to see the larger ones by RIGHT CLICKING on the image and choosing VIEW IMAGE. If that doesn’t work, try going to the images directly:

Antenna & Radials
Wire Table
Elevation Pattern

Categories: Antenna Modeling