**4nec2 optimization**

In my experience 4nec2's optimization some limitations.

First you need to understand how 4nec2 calculates it's figure of merit from the properties (e.g. gain, SWR). If you specify more than one property, it is important to scale the properties, i.e. an improvement of ? ohms is the same as 1dB. If you use the frequency sweep option, the comparison is done on the average figure of merit across the whole band. (Which doesn't always produce a flat response.) Unfortunately, the properties don't map directly to reception (net) gain.

Second you may need to tweak your variables. For example, take an SBGH with reflecting rods. The driven element has three variables: length of the horizontal wires, length of each of the angled wires, and the distance between the two sides. The reflecting rods add in more variables: distance between the drive element and the reflectors, gap between reflector halves, length of each reflector rods, and vertical placement of each reflector rod.

Whew! The problem comes in when you try to optimize multiple quasi-dependent variables simultaneously. For example, if you are optimizing the driven element, you probably want the vertical placement of the reflector rods to remain relatively the same. So for that you want your variable to be a percentage of the length of the angled wires instead of an absolute distance. (In the same way you should use a variable to calculate the number of segements per wire instead of using a fixed value.)

Finally, the optimizer is based on the assumption the figure of merit is a smooth function with only one maxima. This is kind of like a landscape with only one hill - as long as you always increase in altitude, you will eventually reach the top of the hill. Unfortunately, antenna response curves are much more complex. You may be on top of one hill, but that doesn't mean there isn't a bigger hill somewhere else. (Or, if you overshoot the top of the hill you're on that you won't land on a different hill.)

This is not to say 4nec2's Optimizer isn't usefull. Assuming you can create a reasonable figure of merit, it will happily tweak your design to the micrometer. But if you just feed in your design and click "Optimize" without a little foresight there's a chance you will end up with an even worse antenna.