A method for increasing the dynamic range of the receiver/control unit of an alarm system. The alarm system comprises the receiver/control unit, the receiver comprising at least one antenna apparatus and apparatus for switching the antenna apparatus. The control unit, or processing apparatus, comprises signal detection apparatus and apparatus for controlling the antenna apparatus switching. The method comprises the steps of selecting an input to the receiver, wherein the input maybe an output of one or more antenna apparatus or no antenna apparatus, and detecting the presence of a signal. The basis of the apparatus alarm system is the selection of no antenna, which causes the receiver to be approximately 12 dB less sensitive. The switching of the antenna apparatus is preferably accomplished by processor control of switching diodes. This allows the receiver to detect signals from remote transmitting devices located nearby without saturating the receiver, thereby increasing the dynamic range of the receiver/control unit.