A wireless router's antenna technology generally determines its Wi-Fi signal strength and hence its range. For example, 802.11g wireless routers offered better Wi-Fi range than comparable 802.11b units due in part to technical improvements in their antennas.

802.11n/ac and Wi-Fi Router Range

wireless routers currently offering the best Wi-Fi signal range, however, are 802.11n (sometimes called "wireless N" and 802.11ac units. Where standard 802.11b and 802.11g routers featured just one Wi-Fi radio and antenna, wireless N routers contain two or three radios specifically designed to maximize Wi-Fi range.

Increasing Wi-Fi Range

The standard antennas that ship with wireless routers are almost all omnidirectional - meaning that they distribute their signal equally in all directions. These antennas provide more uniform coverage in a radius, but they also limit the signal's reach in any one specific direction. Some routers support replacement of their standard antennas with upgraded "aftermarket" ones. Many aftermarket Wi-Fi antennas work directionally, their radio signals focused in specific directions. All other things being equal, replacing the omnidirectional antenna on a wireless router with a directional one will increase its maximum range.

Factor to Consider When Choosing Router

Wi-Fi range is just one of several factors to consider when choosing a wireless router . For example, the reach of a wireless network can also be increased by installing wireless range extender products, or by upgrading a Wi-Fi client instead of the router. - See more at: http://trendymediablog.com/2014/09/which-wireless-router-has-the-best-wi-fi-range/

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For some routers, it is not necessary to buy additional antennas. Some models can easily reach one kilometer in radius. Of course, an ordinary router that stands in an apartment is not capable of this, but does it need it? How often do you meet an apartment with a radius of 1 km? Even in a country house with 2 floors. If you install the router in the middle of the house, then you will not have any special problems with the signal quality. If nevertheless someone is interested in this topic, then you can read this article Router https://techprojournal.com/best-wifi-router-for-long-range/ . Here everything is described in detail.