I want to use the built in GSM module on my arduino, but even with my phone I have a bad connectivity in my area, altough it's known for having a good connectivability. So with the arduino antenna i have no connection at all :(. Do you know how i can improve the antenna quality myself by building my own or increasing the power for sending away the data?
Hi @jgartner,
I would strongly suggest buying another antenna instead of building.
Mouser has quite a few options for cellular uFL antennas. Let me know if you need some suggestions.
I would appreciate it if you'd have some suggestions for me 
If you know you have a stronger signal in a particular direction and a fixed Arduino install you could use a YAGI type antenna.
These have a high null point to the rear and rear sides but exceptional forward gain.
If you are unsure then an OMNIDIRECTIONAL type would be a better bet.
Omni's usually have a small NULL point so you may be able to also get a very small directional approach with those too but usually it is minimal.
Would avoid the super cheap "rubber duck" type in favour of something a little better but you may also have to invest in a UFL to SMA patch cord too.
Ensure it is up to 4G capable to get best compatibility and minimum 8dB gain. (more gain is better)
Either will allow you to mount the antenna better than the one supplied.
hehehe, something a little different for you if you have a spare old satellite dish to improve your reception