Like all things, simplified sayings have meaning only if you are very careful. "Bigger is Better" is an antenna thumb rule with a long history, but you need to be careful about its application since bigger also changes things and it may not change them in a way that makes it better for you.
It is important to understand that you are working with an RF circuit and the Smartuner™ is matching an impedance at the feed point to the impedance of the feed line from the transceiver. The impedance to be matched will depend on the frequency, the geometry of the antenna system (not just the radiating element, but the ground radials as well), the environment the antenna is in, and a whole host of little factors like the type of wire and such. The gross effects (frequency, geometry, environment) can be predicted, but it’s usually easier to play with the antenna a bit to see what works best. There are no fixed, best answers. If you look at feed point impedance vs. frequency across the range of a Smartuner, you’ll find it varies quite a bit. For some antennas there will be large peaks and valleys in the curve that may be hard to match. For most people, the environment itself is relatively fixed (tree is only so high, can’t move the house, have to be in the attic, etc), and you want to operate at certain frequencies, so only the geometry of the antenna and RF grounding system are changeable when you have a matching problem.
All of the Smartuners are designed to match as wide a range as possible. The SG-239 has less range than the others, but it’s still wider than other products on the market. However, it’s not infinite. By being willing to experiment a bit, you can optimize your installation. The usual way is to change the antenna or the ground, which shifts the peaks and valleys by shifting the electrical balance at the feed point. With a little experimentation, you can almost always reach a point where you can establish a stable match on all the frequencies you’re interested in using. Sometimes, the best shift is actually to make your antenna shorter, but usually you will want to go longer. You might want to take a look at our technical notes on wire lengths and radial and counterpoises.
The important point here is that thumb rules are great as a starting point, but every situation is different and something that works well enough that people make a thumb rule about it may not work in your particular installation. SGC’s book "HF User’s Guide", has an overview of the issues related to HF installation and operation and includes a section on antennas. You can download a free copy in PDF format from our publications page.
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