Hi, I'm opening this thread in hope to make some order with the GPS issues many of us are having.
There is a lot of misleading information as to the cause and solutions that have nothing to do with fixing the GPS (the 3 pins which are for the volume rocker, for example).
My phone is H850 version, but relevant to all variants.
I would like to thank Rick Jones for putting me on the right track, you can read some on iFixit here
What are the issues?
GPS reception getting worse over time.
Not getting a fix.
Getting a fix but losing signal sporadically.
OK, let's start:
All the "magic" is concentrated in the very top - right of the phone (viewing from the front).
Digging through FCC site for documents, I found this:
As you can see the GPS antenna is top left (view from the back).
It was thought that the antenna is on the metal back, but this is not the case.
In fact, it is on the plastic frame that holds the LCD, sandwiched between the LCD and it's frame.
Here is a photo of an LCD frame without the LCD:
The strip then goes to the other side and under the PCB:
And connects to the PCB here:
and here you can see with the PCB removed:
This is with the PCB in place:
Now, this is the metal back where the grounding mesh is:
Now, to elaborate, The Antenna for the GPS is of a "planar inverted-F antenna" type. (see Wikipedia here)
This is where the grounding part comes to light - It is part of the antenna plane, though not the antenna itself.
The pin(s) mentioned must make good contact between the antenna, PCB, mesh.
Problem is one or both pins do not make good connection to PCB/mesh. this can happen over time.
Adding some additional layer in the form of a conductive foil, yields better connection (see photos, they explain what to do).
I did this on my phone, and reception became very good, though not exceptional when I compared to other phones.
I usually get 5-10 meter accuracy outside. While certainly good, should be 3 meters or better with GPS+GLONASS+BeiDou.
And indoors close to a window, I get better accuracy and fix time with other phones.
A strange thing that might be software related, I get much better results both in fix time and accuracy, while using the diagnostic menu (*#546368#*850# on the dialer and "field test" then do "GNSS POS test")
when compared to apps like "GPS test"
Not satisfied with this, I decided to find a better solution for the pins, and found a suggestion to replace/solder on the pins a better connector in the form of a spring contact (similar to the springs on the vibration motor).
I salvaged from some faulty phone, (not G5), those springs an soldered on top of both pins, to make a hopefully long term solution. Also I removed the mesh, cleaned the glue residue as I suspect this is part of the problem.
While this did NOT improve the reception, it does work fine. However, it does have the risk that you can damage the pins/PCB, so unless you have good soldering skills, I suggest avoiding this and using the foil method.
Some extreme close-up photos of the springs soldered on the pins:
To summarize, the antenna is in 2 parts - 1. the flex strip to the LCD frame, 2. the ground plane to the metal back.
The pins, probably through stress, heat, lose good contact to their relevant mates.
The other solutions (such as the 3 pins which was PROVED to be the volume rocker) gives temporary, if at all, solution because all it does is lift the PCB and not even on the correct side - avoid THIS IS FALSE.