Unlike Indoor usage, ability to calculate radio link budget & distances is very critical if one wants to use Wireless LAN equipments for bypassing Telco’s last mile. Those who has very minimal radio knowledge might having some difficulties in doing it. Fortunately, carries a simple radio link calculation accessible from the Internet. It includes all the formulas and, thus, anyone can always write their own routines in Excel. I would strongly suggest for accessing the site for playing with the radio link calculation.
There are several critical parameter needs to be calculate properly to make sure the system will correctly perform, namely,
- System Operating Margin (SOM), it correlates the transmitter power, type of antenna, length of coaxial cables and distance. We can make sure if our system has a sufficient power margin to reach such distance.
- Free Space Loss (FSL), loss in radio power in reaching certain distance.
- Fresnel Zone Clearance (FZC), to see the required antenna height needed to pass any obstacle.
- Antenna bearing, antenna down tilt, and antenna down tilt coverage radius are needed to know the exact point or area of your radio beaming into.
A power conversion calculation utility is also provided to convert dBm into Watt vice versa. The conversion is fairly simple, i.e.,
dBm = 30 + Log 10 (Watts)
Watts = 10^((dBm - 30)/10)
MilliWatts = 10^(dBm/10)
The calculations provided in YDI.COM is in miles and feet, and, thus, one need to convert into meter if needed. For your convenient, the following is the needed conversion table
Meter = Feet * 0.3048
Km = Miles * 1.609344