This tool computes the maximum range or distance that can be achieved with a 20 dBi gain antenna.
The system includes a transmitter, receiver, antennas and cables.
To calculate the max distance, enter the following:
- Frequency of operation (Hz/KHz/MHz/GHz)
- Transmit Power (dBm)
- Receiver Sensitivity (dBm)
- Receive Antenna Gain (dBi) – the default value is 2 dBi
- Total Cable and Other Losses (dB)
The calculator uses the Free Space Path Loss (FSPL) equation:
PTx – PRx = 20*Log10(d) + 20*Log10(f) + Lc + 20*Log10(4π/c) – GTx – GRx
The distance d is given by
Log10(d) = (1/20)*(PTx – PRx – Lc + GTx + GRx – 20*Log10(f) – 20*Log10(4π/c))
Example Range Calculation
At a frequency of 1000 MHz and transmit power of +10 dBm, let’s calculate the range for a 20 dBi antenna
- Receiver sensitivity = -90 dBm,
- Receive antenna gain = 2 dBi, and
- Cable loss = 0 dB
the maximum range is 30,035 meters or 30 km.
Important to remember that this calculation is outdoors and free space which represents an ideal signal propagation condition. In practice, the range would be lower.
If you want to use a 20 dBi (receive) antenna for TV signal reception, use the calculator above. Consider the frequency of operation, transmitter power (in the kW range) and transmit antenna gain.
How to use the calculator
Below is a list of the terms used in the calculator and what each of them mean.
Frequency of operation
This is the frequency at which the communication system operates. At lower frequencies, wavelength is commonly used and if that’s the case, then use the wavelength to frequency converter.
This is the power at the output connector of the transmitter. It is usually specified in dBm. However many vendors specify this quantity in Watt. Convert from Watt to dBm.
Transmit Antenna Gain
This depends on the type of antenna used and is expressed in dBi (dB relative to isotropic antenna).
Total Cable and Other Losses
This includes losses between connectors and antennas. If RF Splitters are used, the loss should be accounted for as well. It is specified in dB. Use this calculator to find the loss due to antenna cable.
The sum of the Transmit antenna power and Gain minus cable and connector losses is also called Effective Isotropic Radiated Power or EIRP for short.
Minimum level of input signal that a radio receiver can detect and demodulate. Use this calculator to find the sensitivity as a function of temperature, SNR and receiver noise figure.
Receive Antenna Gain
Depends on antenna used and is expressed in dBi. In cases where the signal is from a particular direction, a high gain antenna (8 dBi for instance) can be used. This allows focusing of energy instead of receiving from all directions. Antenna gain can be calculated from the Antenna Factor and frequency of operation.
What is a 20 dBi antenna used for?
A 20 dBi antenna is used to increase the range of a wireless system. The picture below shows before and after pictures – where the high gain antenna is used to improve coverage and provide a high quality of service in the home.
 Free Space Path Loss on Wikipedia