If your Wi-Fi router has an attached external antenna it's a relatively simple matter to unscrew the antenna that came with it and connect a cable to a larger external antenna or one that is directional; However, if your wireless router is one with an internal antenna, you'll need to open it up to connect an external antenna to it. Note that cracking open the case of your Wi-Fi router will void the warranty and may damage it beyond repair; so proceed with caution.
Disconnect your wireless router from all external connections. Do not work on electrical components while they are plugged in.
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Remove the case and locate the wireless module. Every wireless router will be different. Proceed slowly and look twice for screws before prying things open. When prying, use plastic tools instead of metal to avoid damaging the case. The wireless module will have one or more miniature UHF connectors on it.
Connect your UF.L pigtail to an empty antenna connector. If the wireless router only has one antenna connection, gently remove the internal antenna connection and attach your pigtail. Center the pigtail connector over the empty antenna connector on the router's circuit board and press firmly downward until it snaps into place. The connection should rotate in two directions, but not lift off of the board when you try to move it.
Locate and mark a spot on the router's case where you want to place the external connector from the pigtail. Cut or drill out the spot with your drill or rotary cutting tool. Sand down the edges. Note that the hole should be the diameter of the connector, but smaller than the diameter of the nut that is threaded onto the connector.
Remove the nut and washer from the connector. Push the connector through the hole in the router's case and place the washer and nut on the outside of the case. Tighten the nut with your fingers until it is snug.
Reassemble the router. Replace any screws you removed and reattach the case.
Screw your external antenna to the newly fitted external adapter.