The 2.4GHz spectrum is free (unlicensed) because it is a terrible bandwidth for reliable communications. Why else would the FCC give it away?
Seriously, the 2.4 GHz frequency is absorbed by water (think microwave ovens) and wood, and what isn’t absorbed is reflected. Think about the 5000+ leaves on a tree blowing in the wind. 5000+ little reflectors interfering with your 2.4 GHz signal. Thus 2.4 GHz signals do best in free space, or in line of sight applications.
Seriously, the 2.4 GHz frequency is absorbed by water (think microwave ovens) and wood, and what isn’t absorbed is reflected. Think about the 5000+ leaves on a tree blowing in the wind. 5000+ little reflectors interfering with your 2.4 GHz signal. Thus 2.4 GHz signals do best in free space, or in line of sight applications. When you think line of sight you probably think about a line, right? Unfortunately it’s not that simple. There is something called a Fresnel zone that defines a cylinder (more or less) through space that needs to be as free of objects as possible in order to get the maximum signal possible. There are free space and fresnel zone calculators available online in many places. • Free Space Loss Formula Free space loss = 36.56 + 20Log10(Frequency) + 20Log10(Distance in miles) • Fresnel Zone Calculations 1st Fresnel Zone radius (Km) = 17.3 x Square root ((Obstacle Distance x (Total Link – Obstacle Distance)) / (Frequency in GHz x Total Link)) 1st Fresnel Zone radius (miles
Related Questions
- The 2.4GHz spectrum is free (unlicensed) because it is a terrible bandwidth for reliable communications. Why else would the FCC give it away?
- Why should I consider the use of licensed spectrum when unlicensed spectrum, such as 2.4GHz for Wi-Fi, is free?
- How does this fit with the FCCs exploration of unlicensed spectrum to connect rural areas?
