Hi karina184.
Many thanks for your input on this issue. My router is in my study on top of a bookshelf and gives clear signal to all our devices including the TV throughout the apartment, even if I close the study door (wood). The TV is on 5GHz and streaming etc is excellent. Our laptops, iPads, etc are all on the 2.4GHz signals and all respond well except for my iPhone X!! We are in Australia and on NBN Aussie Broadband and we have not had any issues since switching to them. Prior to that we had an ADSL connection with Telstra and I had the same problem with my iPhone X with that internet provider. I was hoping the new type of connection and provider would be an improvement but unfortunately not!
I have done lots of experiments including some speed tests on my iPhone X and my hubby's iPhone 8 and checked general performance comparisons. My iPhone test came up as 15.3 download and 13 upload on the 2.4GHz and 54 download and 19 upload on 5GHz (quite a significant difference between the 2 signals!!). On the iPhone 8 I got 22 download 15.4 upload on 2.4GHz and 54 download and 19 upload on 5GHz and the iPhone 8 safari appeared to respond quicker than the X on the 2.4GHz!
The most major difference I found is that the iPhone 8 stays connected to 5GHz regardless of where I am in the apartment, including at the dining room table where the iPhone X loses the 5GHz and it does not even show up on the screen to reconnect unless I move away from that spot!! This has more or less convinced me that the iPhone X itself appears to have the problem.
I rarely if ever use public internet connections, so I have yet to see if that shows any change? I have done all the usual stuff, turn off turn on, reset network settings etc etc.
At least with Jeff's and your assistance, I have now narrowed down that the X will work great without its cover on and when on wifi as long as it can pick up the 5GHz in our apartment, and that the only dead spot is at or near our dining room table!! I will now need to decide whether I go to Apple to see if there is a fix (have my doubts judging by other blogs on the X and wifi issues) or put up with it until it's time for the X to go to "phone heaven" which, with the increasing costs of iPhones, won't be anytime soon!! Shame as otherwise it is a fantastic phone!!
Thanks again to you both, as it has helped me understand my phone better and when I need to just turn off the wifi and use mobile data, which always works perfectly inside or outside!! Worse part is remembering to switch wifi back on!!
Regards
Maria