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Wifi on 5Hz works good, much better than on 2.4Hz. Other phones can find not only my wifi, but my neighbors wifi too. So its problem in iPhone 8. What I should to check? Thanks!
Wi-Fi antennas on iPhones are generally connected at the top left of the logic board. Sometimes an antenna may not be connected properly or the screws are not in the right spots which may not allow the antenna on the housing to contact properly with the logic board antenna contacts.
There are 3 possible parts that could be giving you issues, the black plastic square antenna at the top left, the flex at the top middle that connects near the rear camera, and one that connects next to the battery connector and goes over the loud speaker. For a guide on screw sizes do a google image search for iPhone 8 screw guide.
