Hi dani,
excellent perormance here, and very happy with the GP 1090 since about one year. Of course, its location has the most important influence, as the antenna cannot "see" through" obstacles, and "line of sight" rules apply for wave propagation at those frequencies it is about. So keep it up "as high as possible", use a "very low loss" feeder coaxial cable with the proper connectors carefully attached to its ends. But also keep in mind, that in case you exceed cable lenghts of about 10 meters, preamlification (by means of a "masthead amplifier" [Wimo]) is reqired to compensate for cable losses.