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Before we start using the Wireless LAN Calculator, it is useful to understand how is works.

It is important to gather the environmental information before doing the physical setup.
Imformation include :
1. Suitable locations for mounting the devices
2. Background noise. If there is too many devices using 2.4GHz band in the region, you can consider 5GHz.

Fade margin is the difference, in dB, between the magnitude of the received signal at the receiver input and the minimum level of signal determined for reliable
operation. Higher the fade margin, the more reliable the link will be. The exact amount of fade margin required depends on the desired reliability of the link, but a good rule of thumb is 20 to 30 dB. Fade margin is often referred to as "thermal" or "system operating margin".

Fade Margin = Received Signal - Receiver Threshold

where
Received Signal = Tx Power - Tx Cable Loss + Tx Antenna Gain - Free Space Path Loss + Rx Antenna Gain - Rx Cable Loss
Received Threshold = Receiver Sensitivity

To use this calculator, you need to input the required distance and select transmitter & receiver access points, optional cables & antennas.


From the Fade Margin equation, Free Space Path Loss can be computed with the following equation.
Free Space Path Loss = Tx Power - Tx Cable Loss + Tx Antenna Gain + Rx Antenna Gain - Rx Cable Loss - Rx Sensitivity - Fade Margin

Free Space Path Loss can also be computed with the following equation.
Free Space Path Loss = 32.44 + 20 log10 FrequencyMHz + 20 log10 Distancekm

With the above two Free Space Path Loss equations, we can find out the Distance in km.

Distancekm = 10 (Free Space Path Loss - 32.44 - 20 log10 FrequencyMHz) / 20

To use this calculator, you need to input the fade margin and select transmitter & receiver access points, optional cables & antennas.


The Fresnel Zone is the area around the visual line-of-sight that radio waves spread out into after they leave the antenna. You want a clear line of sight to maintain signal strength, especially for 2.4 GHz wireless systems. This is because 2.4 GHz waves are absorbed by water, like the water found in trees. The rule of thumb is that 60% of Fresnel Zone must be clear of obstacles. Typically, 20% Fresnel Zone blockage introduces little signal loss to the link. Beyond 40% blockage, the signal loss will become significant.

Fresnel Zone Radiuskm = 17.32 x Squareroot ( Distancekm / (4 x FrequencyGHz) )

To use this calculator, you need to input the fade margin and select transmitter & receiver access points, optional cables & antennas.


To find a suitable antenna, it can be done by calculating the antenna gain from the two Free Space Path Loss equations.
To find out both Transmitter and Receiver Antenna Gain (assuming that they have the same value)

Tx or Rx Antenna Gain = (Fade Margin - Tx Power + Tx Cable Loss + Rx Cable Loss + Rx Sensitivity + 32.44
+ 20 log10 FrequencyMHz + 20 Log10 Distancekm) / 2

To find out Transmitter Antenna Gain (assuming you have Receiver Antenna Gain information)

Tx Antenna Gain = Fade Margin - Tx Power + Tx Cable Loss + Rx Cable Loss + Rx Sensitivity + 32.44
+ 20 log10 FrequencyMHz + 20 Log10 Distancekm - Rx Antenna Gain

To use this calculator, you need to input the distance & fade margin and select transmitter & receiver access point, optional cables & receiver antenna.

To find out Receiver Antenna Gain (assuming you have Transmitter Antenna Gain information)

Rx Antenna Gain = Fade Margin - Tx Power + Tx Cable Loss + Rx Cable Loss + Rx Sensitivity + 32.44
+ 20 log10 FrequencyMHz + 20 Log10 Distancekm - Tx Antenna Gain

To use this calculator, you need to input the distance & fade margin and select transmitter & receiver access point, optional cables & transmitter antenna.
Note : You must select "Find this" for at least one of the antennas.
With the computed antenna gain value, you will be able to find the closest matching antennas.