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GPS issues demystified

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By shloms, Junior Member on 20th November 2017, 11:09 PM
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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:
Click image for larger version

Name:	ZNFH850.jpg
Views:	26322
Size:	127.0 KB
ID:	4337847

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:
Click image for larger version

Name:	frame.jpg
Views:	29822
Size:	95.7 KB
ID:	4337810

The strip then goes to the other side and under the PCB:
Click image for larger version

Name:	GPS_strip.jpg
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Size:	230.5 KB
ID:	4337812

And connects to the PCB here:
Click image for larger version

Name:	gps4.jpg
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Size:	234.4 KB
ID:	4337823
and here you can see with the PCB removed:
Click image for larger version

Name:	gps3.jpg
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Size:	253.8 KB
ID:	4337822
This is with the PCB in place:
Click image for larger version

Name:	gps2.jpg
Views:	19948
Size:	189.4 KB
ID:	4337821

Now, this is the metal back where the grounding mesh is:
Click image for larger version

Name:	gps1.jpg
Views:	21898
Size:	249.4 KB
ID:	4337820

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:

Click image for larger version

Name:	1116_1.jpg
Views:	21694
Size:	105.8 KB
ID:	4337842
Click image for larger version

Name:	1116-2.jpg
Views:	20680
Size:	65.0 KB
ID:	4337843
Click image for larger version

Name:	1116-5.jpg
Views:	17856
Size:	47.4 KB
ID:	4337845


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.
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20th November 2017, 11:31 PM |#2  
askermk2000's Avatar
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Yep. You're right.
I checked out the posts here where people where offering elaborate soldering of wires, or that volume rocker connection. I quickly found a post, or site, elsewhere that described the same as you and I knew that was correct almost immediately.
Actually it probably was that iFixit page you mention.
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21st November 2017, 05:42 AM |#3  
ChristopherXI's Avatar
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Quote:
Originally Posted by shloms

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:
Attachment 4337847

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:
Attachment 4337810

The strip then goes to the other side and under the PCB:
Attachment 4337812

And connects to the PCB here:
Attachment 4337823
and here you can see with the PCB removed:
Attachment 4337822
This is with the PCB in place:
Attachment 4337821

Now, this is the metal back where the grounding mesh is:
Attachment 4337820

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:

Attachment 4337842
Attachment 4337843
Attachment 4337845


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.

Can you look over to the Antenna3 (top middle) and help me with my Cell reception problem? The phone's reception is horrifyingly terrible.
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22nd November 2017, 07:36 PM |#4  
You are right , this helped me. I got this images from some forum post.]I tried the three contact one but that was just a dumb idea and broke my volume up
Don't try the three pin (those are volume contact points)method anyone who come here please read this
Attached Thumbnails
Click image for larger version

Name:	lg gps 3.jpg
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Size:	122.2 KB
ID:	4339584   Click image for larger version

Name:	lg gps 2.jpg
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Size:	31.8 KB
ID:	4339585  
23rd November 2017, 01:34 PM |#5  
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Thanks Meter: 32
 
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Quote:
Originally Posted by ChristopherXI

Can you look over to the Antenna3 (top middle) and help me with my Cell reception problem? The phone's reception is horrifyingly terrible.


Hi, I opened this thread for GPS antenna, but I'll try to help

Which model of the G5 you have and which frequencies? Also is the reception bad on LTE, 3G, GSM, which?
Any how take a look at those photos, to see where the contacts for ANT3, should you check:
Click image for larger version

Name:	pcb dwn.jpg
Views:	4980
Size:	145.0 KB
ID:	4340158

Click image for larger version

Name:	PCBUP.jpg
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Size:	188.9 KB
ID:	4340159

Click image for larger version

Name:	BACK.jpg
Views:	4826
Size:	156.7 KB
ID:	4340160
23rd November 2017, 05:20 PM |#6  
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Great thread thanks alot Shloms!
that will be helpful to many people.

Quote:
Originally Posted by prannoytambe

You are right , this helped me. I got this images from some forum post.

Thats the wrong one!
it may work because it's the ground connection but the actual GPS antenna is the one above.
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23rd November 2017, 05:33 PM |#7  
Quote:
Originally Posted by thetool

Great thread thanks alot Shloms!
that will be helpful to many people.



Thats the wrong one!
it may work because it's the ground connection but the actual GPS antenna is the one above.

oh might be mine had ground issue, but will try the other one once i open it for the vol button fix.
Still please lets help boost this post , other are killing peoples vol button with no fix.
23rd November 2017, 09:34 PM |#8  
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Hi, I'm using Rs988. I live in Ukraine and here the operators support only 2g and 3g. The phone does not catch the signal of all operators. I think that the problem is in the antenna. As I understand the antenna for wcdma, gsm is at the bottom of the phone. How to improve the signal?

Отправлено с моего RS988 через Tapatalk
23rd November 2017, 11:23 PM |#9  
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Quote:
Originally Posted by spinoza_web

Hi, I'm using Rs988. I live in Ukraine and here the operators support only 2g and 3g. The phone does not catch the signal of all operators. I think that the problem is in the antenna. As I understand the antenna for wcdma, gsm is at the bottom of the phone. How to improve the signal?

Отправлено с моего RS988 через Tapatalk

Yes for 2G, and some of the 3G it's the antennas on the removable battery "chin"
Click image for larger version

Name:	ZNFVS987.png
Views:	2208
Size:	91.4 KB
ID:	4340601
This is for your model.
However, as you can see some of the 3G are shared with Antenna 3 on the top.
You can check the Bottom removable part if the 2 contacts make good connection with PCB.
Click image for larger version

Name:	bottom.jpg
Views:	2194
Size:	48.8 KB
ID:	4340615
Do you get good signal with other phones?
25th November 2017, 08:24 AM |#10  
ChristopherXI's Avatar
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Quote:
Originally Posted by shloms


Hi, I opened this thread for GPS antenna, but I'll try to help

Which model of the G5 you have and which frequencies? Also is the reception bad on LTE, 3G, GSM, which?
Any how take a look at those photos, to see where the contacts for ANT3, should you check:
Attachment 4340158

Attachment 4340159

Attachment 4340160

Using the At&t version. the reception is bad on all LTE/3G/2G
26th November 2017, 01:39 PM |#11  
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Another post a while back used liquid nickel epoxy. Can be found on Amazon on the cheap to basically dab extra material which would harden creating a contact surface. This would be a lot more practical than soldering on new springs.
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