dBi
DBi (noun) means a unit of antenna gain, measuring in decibels how much more strongly an antenna radiates or receives in its best direction compared with a theoretical isotropic antenna that radiates equally in every direction. A higher dBi figure means a narrower, more focused beam and greater range in that direction. Example: “The router shipped with 5 dBi antennas, which I swapped for 9 dBi ones to reach the garage.”
How to Use DBi
Learner’s notesIn plain EnglishA number telling you how focused an antenna's signal is, and so how far it reaches in that direction.
Technical. Written with a lower-case d and capital B, as with all decibel units.
Fill the Gap
Can you complete this real example?
The router shipped with 5 _____ antennas, which I swapped for 9 dBi ones to reach the garage.
Etymology
From decibel plus i for isotropic, the idealised reference antenna against which the gain is measured.
Frequently Asked Questions
What is the difference between dBi and dBd?
dBi compares an antenna with a theoretical isotropic radiator, while dBd compares it with a half-wave dipole. A dipole itself has about 2.15 dBi, so you convert by adding 2.15 to a dBd figure to get dBi.
Does a higher dBi antenna always mean better Wi-Fi?
No. Higher dBi does not add power, it concentrates it into a flatter, narrower beam. That helps over distance on one floor but can leave rooms above and below with a weaker signal than a lower-gain antenna would give.
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