Antenna Gain (dBi)

Antenna gain in dBi tells you how much more strongly an antenna focuses energy in a chosen direction compared with an ideal isotropic radiator, which would spread power equally in all directions. The linear gain ratio is converted to decibels with 10\log_{10} because gain is a power ratio, and the logarithmic scale makes large comparisons easier to handle and add together in link budgets. A higher dBi value means a narrower, more directional radiation pattern, not that the antenna creates extra power.

Use this when converting a known linear antenna gain into dBi, or when comparing antennas in RF, Wi‑Fi, cellular, satellite, or radio link design. It is especially useful in link budgets and coverage calculations where gain values are expressed on a logarithmic scale.

• Using 20\log10 instead of 10\log10, which is for voltage or field ratios, not power gain
• Forgetting that dBi is a relative measure compared with an isotropic radiator, not an absolute power unit
• Applying the formula to a loss value without first converting it to a proper linear gain ratio