 Hey everybody, it's Hostos with RF Alamance and today we're going to talk about my favorite subject, side lobes. The radiation diagram of an antenna tells us how strongly it radiates in any given direction. The main lobe has the highest gain and most antennas only have one main lobe. All the lobes other than the main lobe are considered side lobes. The size of the side lobes depends on the type, the size, and the construction of the antenna. It's important to understand that through side lobes, antennas transmit but also receive signals from unwanted directions. The requirements of side lobes vary depending on the application, but in general, side lobes are a huge no-no. For point-to-point applications, we want to deliver as much energy as possible to a single point and any side lobes means part of it is wasted. For area coverage applications like sector antennas, we want to avoid all side lobes outside the main lobe. Antennas side lobes are extremely harmful in fixed wireless networks. Any signals radiated in unwanted directions is noise for any other radio in the area and vice versa, any signals received from unwanted directions is noise for your own radio. Side lobes increase the noise level and therefore should be avoided at all costs to ensure sustainable use of the spectrum. Whether the spectrum is licensed or unlicensed, it doesn't matter. However, the point-of-no return is achieved quicker in unlicensed bands due to the uncontrollable amount of devices deployed. Side lobes are often judged by so-called side lobe levels or front-to-back ratio. Side lobe level is the difference between the gain of the main lobe and the gain of the strongest side lobe. Front-to-back ratio is a difference between the gain of the main lobe and the back lobe. Most antenna manufacturers often misuse front-to-back ratio as the measure of side lobe suppression while it only gives information about the gain of the back lobe. It says nothing about the rest of the side lobes an antenna might have. This is an example of antenna with good front-to-back ratio but horrible side lobes. But this is an antenna with average front-to-back ratio but almost non-existent side lobes. Front-to-back ratio is merely a marketing gimmick. When you look at a 3D radiation diagram and everything about side lobes becomes very clear. More on 3D diagrams in some of our upcoming videos.