antenna not receiving full WIFI signal?

Hi @subhanaamir

It could be due to a loose or faulty WiFi antenna cable in the phone.

Here's a composite image taken from this teardown video showing the antenna connections at both ends i.e. mainboard end and the sub board end.

(click on image)

Check if some how water or any gets in to your phone, once my Oneplus 8 pro dipped into a river for few seconds. Phone was working but the network was totally gone for that day. At night i opened up the phone using a pry tool and with a dry brush cleaned all the water. Then Boom Notwork started to work.

Bear in mind wifi antennas are polarised (horizontally or vertically). I assume your router has at least two antennas. If all the other suggestions tried so far didn't deliver required results, try this:

Make sure the antennae are screwed in tightly to your router. Then test reception (signal strength) after orienting both antennae first vertically (pointing upwards) then horizontally (pointing sideways). Then both in between these two orientations then orient one antenna vertical and one horizontal then both antennae in various arbitrary orientations.

As you probably know, signal strength only indicates exactly that and not your Internet signal. The wifi signal is the 'carrier' energy for whatever information is needed to be transmitted - for example the Internet information you get via your ISP. IOW even if the Internet is down, you should still see the wifi icon indicating that your router is OK and transmitting the carrier wave even though it carries no (Internet) information.

In rare cases strong RF microwave frequency interference transmitting close to the frequency your router's carrier frequency operates at may 'swamp' your router's signal or your phone's receiver and cause weak signals to your device. Many wireless items unfortunately today operate at these frequencies (microwave ovens, door chimes, cell phones, rf remotes, neighbours' wifi routers, even airport radar systems - especially military radar).

This is a long shot but certain metallic items close to a router may absorb signal power (ever noticed the mesh screen on the inside of your microwave oven door - well that 'absorbes' and prevents radiation from exiting the oven).

Lastly. If everything else seems to be in order in your house and it still receives a weak signal, start eliminating the cause: is it just your phone, is it the router itself or its antennae orientation, is it the router's position, is it outside or extraneous interference or absorption, is it your phone's orientation, etc etc. Then try your phone's reception elsewhere with a different wifi setup in a different lication. And definitely try with another phone as well. Some variable ought then to show up and point to a possible solution.