[Nexus 4 General] bla_laber:
Just wanted to share my experiences regarding screen replacement and gps fixing time.

Never had problems with the gps on my n4. then, I had to replace my screen. I bought a spare part from ebay which was no original lg screen (lcd with digitizer). Since then, I had some issues getting a fast gps fix. Satellites are detected quickly, but not fixed. Fixing times were around 30-60 s (or much longer) depending on weather etc. Of course, this was not satisfactory so I started reading stuff here and everywhere else.

First I checked the shielding of the digitizer chips. Shielding was wrapped around the complete digitizer as expected similar to the original one.

Then I played around with extending the antenne for gps. I connected some wires to the push pins without effect. It even got worse. Also, connecting some aluminum foil as described above didn't resolve the issue. But both didn't surprise me (but still I tried ;) ). Since the gps signals are carried by a certain carrier frequency, your antenna has to match this certain frequency as close as possible. How is this matching realized? It is completely done by the design of the antenna. Depending on this, your antenna will have a certain electrical resistance (length of the wire/foil), inductance (loops and windings of the wire) and capacitance (hard to describe =) ). These three factors determine the electrical resonance frequency which has to match the gps signal frequency. If it does not, you will never get a signal. If it does, you will get a signal but still have no information about signal strength, since matching =! matching -> damping has to be as small as possible (if you are interest, google for quality factor of resonant structures), and this is where it gets interesting and engineering and simulations are required (there are a lot of scientific works ongoing about optimizing antenna designs for various needs...).

Long story short: I think it is more or less luck that you get a better gps signal by connecting foils or wires to the gps antenna contacts. By coincidence, your "design" fits to the required frequency. But in most cases, it wont.

The story goes on: Last week, my screen broke again. I got a retired, not working N4 from a collegue. Fortunately, the screen was working and was an original one from lg. So I took it apart and put the screen into my device. Now, with the original screen and original digitizer, I get a gps fix within 6s (clear sky) without any antenna additions.

My conclusion is: avoid cheap screen replacements at all costs. Better pay some more to get hardware with satisfactory quality:

- First, my screen replacement had a terrible bright spot in the middle of the screen.

- Further, battery consumptions was higher (never got more than 2h of screen on time despite trying various roms, kernelns, uv, uc, governers, ...).

- Last, and this is the important point for this thread, noise due to the digitizer is worst. I guess the shielding is not able to protect all other circuits and antennas from the hughe noise by the digitizer chips. Thus, the signal collected by the gps anntena also is polluted by this noise and very good signal is mandatory to get a gps fix (if you are interest google for signal-to-noise-ratio).