Does your router have dead WiFi spots or lack in distance? Then buying a better antenna can boost signal quality and is a cheap and easy solution. Antennas can also be used with WiFi adapters that have a screw on antenna.
Most routers using a stock antenna have a range up to 300 feet. The same router with a external parabolic antenna in theory can go up to 20 miles.
The bowl shape of the parabola would have to be tuned to line of site and no obstructions in the way.
Of course this is what a good antenna and signal can do in theory. In real life getting 20 miles from a router is all but impossible, but increasing a routers WiFi distance can be done.
WiFi Antenna Basics
Antennas are rated by dBi with a lager dBi number being a larger antenna.
Small antenna that come with a router(usually 3-5 dBi) are good up close since the WiFi signal wave has not expanded yet.
As a radio wave travels away from its source the wave expands from its low peak to high peak.
To get a good signal an antenna must be large enough to capture both the high and low peak as it moves.
Will a Larger dBi Antenna Help You?
If you are looking to increase distance than yes a larger dBi antenna will help.
A larger antenna will not help with obstructions such as walls or trees.
To get a better signal past obstructions WiFi boosters are a better option or a router with a high gain.
Things To Check First
Many routers have a signal booster setting that can be increased. This can be checked by logging into the router and looking for a power increase setting.
Repositioning a router higher up and adjusting the antenna can also help in some cases.
Router Antenna Connector Types
The most common connector is called Male SMA followed by Male TNC. The only way to know for sure what type of connector your router anntena uses is to Google the model number and its specifications.
Alternatively it can be unscrewed and examined in pictures before buying one.
2.4 GHz and 5 GHz Dual Band Antennas for WiFi
Super Power Supply 3 x 9dBi 2.4GHz 5GHz Dual Band WiFi RP-SMA Antenna for Routers Asus RT-AC66U RT-N66U RT-N16 AC1750 D-Link DIR-655 DIR-665 N900 Buffalo WZR-HP-G450H Netgear Nighthawk R7000 Linksys
Rated at 9 dBi this dual band antenna comes in a package of three for routers that have more than one antenna.
Super Power Supply® 1x 9dBi 2.4GHz 5GHz Dual Band WiFi SMA Antenna for Foscam FI8908W FI8918W FI8909W FI8910W FI8916W FI8602W FI8608W FI9802W FI8904W FI8905W FI9821W WiFi IP Camera Removable Omni Directional Antennas Network Extension Mini Wireless WAN Long Range Booster
Rated at 9 dBi this dual band antenna is possibly the cheapest on the list.
Alfa APA-M25 dual band 2.4GHz/5GHz 10dBi high gain directional indoor panel antenna with RP-SMA connector (compare to Asus WL-ANT-157)
Rated at 8 dBi for 2.4 GHz and 10 dBi for 5 GHz this is a good option over a stock router antenna.
TP-Link 2.4GHz 24dBi Directional Grid Parabolic Antenna, N Female Connector, Weather Resistant (TL-ANT2424B)
Rated at 24 dBi this parabolic antenna is for someone looking for a serious WiFi signal increase.