It's just Dell notebook. But your advise with channel width 20Mhz is the point. I changed settings of Dell wifi adapter from 20Mhz only to 20/40 Mhz auto and it starts working correctly! Thanks!

Model : Hardware Version : Firmware Version : ISP : Hello I have problem with newly bought powerline wifi adapter WPA4530 v1. Every devices seems work fine, but the problem is with my notebook Dell...