Interference in the vicinity of a receiving radio system can cause serious degradation of the radio communication performance. This may even result in disruptions and lost calls. For a co-location scenario of several communication systems, the combination of output powers will affect the total Signal-to-Noise Ratio (SNR) for receivers involved. In this paper, we show the dependence between output power, antenna coupling, out-of-band characteristics and communication distance. We present results of how these parameters can be combined to guarantee that necessary interference requirements in terms of SNR are met. Furthermore, it is shown that under certain conditions, the maximum achievable SNR only depends on the physical geometry of the co-location scenario.