Antenna Fundamentals - Gain

Antenna Fundamentals - Gain

Do you really need all that gain ?

When looking for Antennas its easy to fall into the trap of “the bigger the better”, however in some situations this can be quite the opposite! In this blog we are going to address some of the very basics about antenna gain and things to look for and consider when making your selection. 

It’s very easy to see a manufacturer advertise a “high gain antenna” think it must obviously be better than the non-high gain version and that’s the one you want. But this really is dependent on your application, for example if you are mounting a directional antenna and know the source of the signal then great, the higher the gain the better for that specific scenario (in the real world this could be a television antenna). However if you’re looking for an omni-directional antenna for a mobile piece of equipment such as a smartphone that can be held in any orientation and can be in any position relative to the network tower then its preferred to have a low gain antenna.

Some of you reading are probably saying “Yes that’s all good and well but what is gain?”, well gain is what we call the increase in signal using an antenna to put it simply and we measure it in dBi. With an antenna the increase in signal is not due to some amplification of signal but the redistribution of the available Radio Frequency (RF) signal into a preferred direction. The base measurement of gain (dBi) is based on measurements for an isotropic radiator (this is an idealistic model that has the same value measured in all different directions).

So how does this apply? well as we briefly mentioned before it really does depend on your specific application and what results you are wanting. You can have an omni-directional antenna with high gain and this will push the radio frequency further creating a larger area of coverage which sounds great, however this will have a negative impact on users in closer proximity to the antenna causing slower speeds and an overall worse connection. And if for example you’re using this high gain antenna to generate a Wi-Fi hotspot at a public park then the mounting of this antenna would be crucial as when you reach higher gain the signal begins to radiate out more horizontally and reduce its vertical spread, so if the router and antenna is connected to the top of a lamp post then the signal might not be detected by any potential users!

Now we aren’t suggesting a high gain is bad, as in some situations will require a high gain in order to function. As mentioned before a directional antenna will typically benefit from having higher gain as they don’t radiate signal in a 360 degree area and are typically used when you know the source of the signal. This allows the directional antennas to reach signal from much further a field whereas if it was using a low gain it may not reach the signal at all!

To conclude we have some foundation on what sort of things we need to consider when selecting antennas and we have tried to provide some real world scenarios to help relate this new found understanding to your specific applications. However if you are still struggling to find the antenna for you or are uncertain between a few of your options then we are here to help!