Knowledge Base

Line of sight propagation means that the broadcasting tower is visible to the receiving antenna, this does not mean you can necessarily see the towers, but the antenna is not blocked. It is also referred to as free space receiving conditions. The theory of Electromagnetic propagation states that free space receiving conditions are achieved if the first Fresnel ellipsoid is free of obstacles. As an example, that means that for receiving TV signal at a distance of 60 miles in free space conditions, the height of the path between transmitter and receiver should be around 330 feet above ground. In the practice, the broadcasting antenna is normally placed at a height such to overcome the curvature of the earth, but this does not usually happen with the receiving antenna. Also, obstacles the receiving path may encounter beyond the horizon are not seen by the naked eye and may mistakenly lead to the idea that we have free space receiving conditions. Should this happen, some additional loss has to be added, further reducing the received power. Therefore, the antenna that receives in non line of sight conditions must have height, directivity and gain, plus low noise like the DAT BOSS LR, where LR stands for Long Range.