Is More Antenna Gain Better?

"Why Bigger Isn’t Always Better? ----- FMUSER "

#Directivity
The true answer to the question “is more gain better” lies in your application. 

For example, if you remove the reflector from your flashlight, have you made it better? Probably not, assuming that you still want a flashlight. However, if you wanted an omnidirectional light source to evenly illuminate a room, then you have made it better! What if you had a lens that concentrated all of the bulb’s light into a narrow laser-beam, would it be better? The answer is “yes”, if you want a laser pointer, “no” if you want a flashlight, and “definitely not” if you want to illuminate a room! This concentration of light is called directivity, and the amount of concentration is called gain.

Flashlight Directivity Examples

A basic light source (such as a candle or light bulb) tends to radiate omni-directionally. That is to say, it has no directivity, or preference for any direction. The same is true for many basic antennas. These omnidirectional sources are perfect for illuminating a dark room, or broadcasting a wireless signal in all directions. The same basic gain and directivity concepts apply to both antennas and light sources.

See Also: >> What's the difference between "dB", "dBm", and "dBi"?  

#Gain In Light Sources
The purpose of the flashlight reflector it to intensify the limited brightness of the light bulb. 

The apparent increase in brightness is not an amplification of light, but simply a collection and redistribution of available light into a preferred direction. This apparent increase in brightness is called “gain”, even though no new light is generated. 

This is done at the expense of most other directions, which lie in darkness. That is why you have to point a flashlight, it is inherently directional (has directivity). This apparent increase in brightness (compared to the bare bulb) is qualified as a ratio, called gain. 

If the flashlight beam is 100 times brighter than the bare bulb, it is said to have a gain of 100X. The laser pointer takes this directionality one step further. Gain is often expressed on the dB scale, and we have more information here.

Perhaps because we can literally see this light, the concepts of gain and directivity are self evident when we talk about flashlights. At our lab, we often make these antenna/flashlight comparisons to help customers understand basic antenna test results.

Increasing Gain and Directivity In Antennas

See Also: >> Field Intensity Units 

Gain In Antennas
Gain and directivity are no different in antennas. 

The fact that we can’t immediately see the RF waves confuses most people. Trying to understand antenna gain with mathematical expressions is no help either! To understand antenna gain and directivity, continue to visualize light sources. 

Then you can answer the question “is more gain better”? Once you know what gain really is, you can determine if more (or less) is better for any particular application. When you want to focus all of the light from a small bulb and direct it to a distant target, then the high gain from a flashlight reflector is definitely the best “antenna” choice. Flashlights and high gain antennas need to be pointed in a preferred direction. 

While we know that new RF power is not being created by the antenna, its directivity sends the RF signal to where it is desired. However, if you want to broadcast evenly to a whole room (or give omnidirectional access to your wireless signal), we do not want gain (or it’s directivity). Remember “gain” is simply stealing radiated energy from some directions to intensify others. This is true for both light or RF signals. Gain comes with directivity, and we don’t always want it. More gain is not automatically better, it depends on the application. If you don’t intend to point your antenna in a particular direction, then you don’t want gain.

See Also: >> Understanding Antenna Gain Basics

#Antenna Gain Patterns

The illustration of an antenna’s gain in various directions is called an antenna pattern. Our antenna patterns reveal gain and directivity. All sources have some directivity, and the variations in gain over various directions is the directivity of the antenna. 

Even an omnidirectional light source such as a candle flame, has a blind spot created by the candle wax. And even omnidirectional antennas have this “blind spot” or “nulls” in their radiation patterns.

 

Our anechoic chamber antenna testing is the only way to map these effects and visualize your antenna’s radiation patterns. High, medium, or “no” gain antennas are all patterned by us, to visualize the nature and amount of their directivity in their preferred direction. This insight will give you the confidence to choose which antenna is best!

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