Wireless range extenders are great for bringing Wi-Fi signals to places your router just can't reach, and they do so using a communications principle that has been used for many years in radio communication -- the repeater. While they do offer the bonus of greater range, there are some drawbacks to using wireless range extenders as well.
Retransmit, Repeat, Rejoice
A wireless range extender, sometimes known as a wireless repeater, receives the signal transmitted by your existing wireless router and rebroadcasts it to computers and devices out of range of the router. In turn, it receives and rebroadcasts signals from your out of range devices to your wireless router, giving you a relatively seamless Internet experience. To ensure the extender works properly, you must place it in a location where it can reach both the existing router and the out of range devices to bridge the gap.
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While this seems like a fantastic idea on paper, and repeaters and extenders do work well, there's no such thing as a free lunch. Because the extender is communicating with two devices simultaneously, your bandwidth is cut in half. This can result in poor performance when watching high definition video or performing other activities that are taxing on your bandwidth, but won't negatively affect basic Internet usage. Additionally, extenders create a second network, and while this network can have the same password as your existing network, devices that move between the range of the two may not necessarily automatically switch to the strongest one.