The measurement of dBi refer to the antenna gain. The dBi measurement are used to indicate how much an antenna concentrate signal power in a specific direction as compared to a theoretical source of signal power that emanates from all direction equally. A higher dBi value does not mean that the antenna is creating more power than an antenna with a low dBi value.
However, a higher dBi value mean that the antenna is focusing its power into a narrower beam. A high dBi antenna will allow the antenna to reach further in one specific direction, but the antenna will provide less coverage of that signal in other direction. Thus, these two variables exhibit an inverse relationship to one another.
How dBi Affects Antenna Range and Coverage
The higher the dBi value, the lower the signal coverage of that antenna. By referring to the chart provided, one can understand how different dBi levels will allow the antennas to have different signal coverages. Antennas with lower dBi values will provide signal coverages that emanate from the antenna’s location and will cover larger area.
In contrast, antennas with high dBi values will focus their signals to only a few area, allowing them to travel further, but limiting the number of areas in which they will deposit their signal. A rubber duck antenna is often used with consumer routers as it provides even coverage of signals in the vertical and horizontal area within a house. A panel antenna or a Yagi antenna could be used if the signal need to travel further.
However, you must aim these antennas in the desired direction of the signal for them to exhibit their range. Thus, each type of antenna can be utilized based on the requirements of the space to be covered. The dBi value of the antenna will have an impact on the antenna’s EIRP, or Equivalent Isotropically Radiated Power.
The EIRP is calculated by the power of the signal that the antenna emits multiplied by the dBi of the antenna. Thus, if the dBi of the antenna is increased, the EIRP will also increase. If the EIRP of the antenna increase to such a level that it reaches the legal regulatory limit for radio frequencies, the antenna may cause issue in the reliability of the wireless network.
Many individuals desire to increase the range of the antenna by increasing the dBi of the antenna’s signal. However, as stated above, this action will increase the EIRP of the antenna signal, causing it to reach outside of the legal regulatory limits. The beam width of the antenna is another factor to consider for indoor application.
Antennas with high dBi values emit signals that have a narrow vertical beam. Thus, the signal will not emanate from the antenna to the floors above or below it. Thus, if the signal pattern from the antenna misses those floor, the antenna will exhibit a strong signal in one room in the house, but it will exhibit no signal in the next room.
For these reason, many mesh networks and consumer routers use antennas with lower to middle dBi values. These type of antennas are less concerned with transmitting the signal as far as possible, but instead aim to provide signal to a three dimensional area. The antenna with the highest dBi value should be selected for the space that is to be covered.
If the space have obstacles in the way of signal transmission from the router to the device, such as walls or furnitures, and if the space to be covered is limited to a single story building, then a moderate gain antenna will be able to effectively transmit the signal to all of the device located in those areas. However, if the device is to be located in another building, or if it is a remote sensor of some sort, a high gain antenna will exhibit more usefulness for those applications. Thus, while the antenna range chart can be used to find the reference points for dBi values for the antennas to be used, the physical demand of the space will help to determine the correct dBi value for that antenna.
You should of checked the room size first. Its important to note that some antennas can absorbs more power if they are placed near metal. It’s also worth noting that the dBi value’s accuracy can vary based off the environment.
Actually, most people dont realize how much the dBi level affects the signal. You’ll need to be careful with your placement so you dont loose signal.