Radiating antennas are usually designed in order to operate within a particular frequency range strongly dictated by the application it belogs to. However, it appears that when considered across very wide frequency (i.e. various decades), antennas may exhibit unexoected behvaiors such as subtantial radiation patterns or reflection coefficient variations. It is then conceivable that an antenna exposed to electromagnetic field signal out of its operational frequency range may present dramatically high gain. In other words the antenna ight not filter this signal. This out-of-the-band aspect needs to be studied.