[Upgrading, Modifying and Unlocking] gluto:
My GPS experience with G2S

Hello..

My pseudo is Gluto.

I am French, in the Nice area.

I received my Jiayu G2S, purchased to jiayumobileshop a few days ago...

All was clear with jiayumobileshop for the order and purchase using Paypal, and with the free, but slow, delivery by China Post.

Rom version of the received phone is G2S 20130306-143807.

It is rooted by default

This phone operates perfectly, the IPS display is really good, touch sensation is quite fluent, colors are bright and neutral, and I am very satisfied of it...

Except of course, for 2 issues:

- Microphone level was a little bit low, and my voice was a little "far", according to the feedback of my correspondents

- GPS "signal to noise" ratio for the received satellites was very poor, between 10 and 25 max, and the lock of the GPS was very slow or impossible. (Displayed using "GPS test")

When locked, Google Maps navigator accuracy was poor, driving more often in the fields than on the road, and the GPS signal was lost every 2 minutes...

1st issue was very easily corrected...

The hole in the back cover is ridiculously small...

After enlargement, I am heard very clearly by my correspondents...

worldwideweb.casimages.com/img.php?i=13041809575135853.jpg

(replace worldwideweb by www)

2nd issue was not so easy...

The 1rst operation was to install "FasterGPS", and to select "Europe", "France", to save this configuration with the suggested server: fr.pool.ntp.org

Lock time fall to less than 30 seconds, in the best receiving conditions...

But it is not reliable at 100%, and the best way remains to proceed, before any GPS use, in the settings of "GPS test" to a "clear AGPS", and "update AGPS" operation..

Fast lock is guaranteed...

But sensitivity remains as poor as before...

I observed that the max SNR was increased from 25 max up to 35 max only with my finger placed on the upper left corner of the phone where GPS antenna is located...

The sensitivity problem was for sure an antenna problem...

I contacted jiayumobileshop for this GPS issue, but I only received 2 time the same prepared mail with GPS use generalities...

And no answer at all when I speak of "Poor conception", "hidden defect", "warranty", or "refund"....

So I decided to fix it myself... I broke the "warranty sealing", and removed the 6 screws of the internal back shell, and proceed to this shell disassembly...

I removed the original antenna sticker, and replaced it by my own antenna using adhesive copper tape, often used for shielding in electronics development, and a cutter...

Have a look to the design on the following photo...

worldwideweb.casimages.com/img.php?i=13041810261033390.jpg

On the motherboard, the lower contact is the ground, the upper is the input signal... My antenna layout drops on the signal contact, and ended with right angle on the ground contact...

Of course, the 2 contacts appears as short circuited together with the copper band, but for a 1.5GHz signal, a few millimeters of copper between 2 contacts is already not any more a short circuit, but a transmission line...

It is a first try... Result is not miraculous, but it provides in average around 8 more in SNR than the original antenna, between 25 and 37, an enough to navigate in my car most of the time on the right road, and without any loss of the signal every 2 minutes as before...

May be it can be slightly more improved, because my finger in regards with the antenna still provides around 4 additional gain and green level of 40 is then exploded...

I hope it will help some of you to fix your GPS problem, but this modification requires a minimum of manual precision...

Regards Gluto...