According to Google...
Using the Friis transmission formula: This formula takes into account the distance between the transmitter and receiver, the frequency of the signal, and the gains of the antennas. It is the most accurate method, but it can be a bit complex to use.
Here's the formula:
Path loss (dB) = Pt (dBm) - Pr (dBm) = 20 log10(d) + 20 log10(f) - G_t - G_r + 27.55
where:
- Pt is the transmitted power in dBm
- Pr is the received power in dBm
- d is the distance between the transmitter and receiver in meters
- f is the frequency of the signal in MHz
- G_t is the gain of the transmitting antenna in dBi
- G_r is the gain of the receiving antenna in dBi
- Using a path loss model: There are a number of path loss models available that can be used to estimate the path loss for different environments, such as urban, suburban, and rural. These models are typically simpler to use than the Friis transmission formula, but they may not be as accurate.
Here are a few examples of path loss models:
- Hata model: This model is commonly used for cellular systems in urban and suburban environments.
- Cost231-Hata model: This is a modified version of the Hata model that is more accurate for higher frequencies.
- Okumura-Hata model: This model is similar to the Hata model, but it is more accurate for long distances.
Once you have calculated the path loss in dB, you can convert it to dBm by subtracting 27.55.
Here are some online tools that you can use to calculate path loss: