Bad derivative

I ordered this tracker in the hope that also the derivative is serving.
The configuration procedure via SMS with the # syntax - self-explanatory and not difficult. Unfortunately, the reception performance of the GSM antenna is extremely bad. All mobile devices that I use here has, without exception, very good reception. Only the Tracker is weakening across the board.
The coordinates that are output are rarely accurate than 50m next to the actual position. In the forest the same reception rips off completely. Unfortunately, proved to be true that the one who buys cheap, buys twice ...