Use this calculator to find the maximum output power of a transmitter in dBm. Enter:
- Antenna gain (dBi)
- Cable Loss (dB)
- Effective Isotropic Radiated Power (EIRP)
PTx = EIRP + LC – GAnt
The maximum EIRP for a LoRa device operating at 922 MHz in Japan is +27 dBm. Let’s say the maximum antenna gain is specified to be 2 dBi.
Using these numbers and a cable loss of 1 dB, the maximum output power from the transmitter is restricted to 26 dBm.
An antenna’s dBi value is a measure of its gain compared to a an isotropic antenna. Isotropic antennas radiate signal equally in all directions. An antenna with a higher dBi value has more gain than an antenna with a lower dBi value.
Antenna gain can be calculated from Antenna Factor and Frequency.
When choosing an antenna for a particular application, it is important to consider its gain. A directional antenna with high gain can be a good choice for applications where you need to maximize the signal strength in a specific direction, such as when aiming a radio signal at a specific target. However, directional antennas can also make it more difficult to receive signals from other directions, so they are not always the best choice for every application.