Typically the performance of radio receivers is distilled to a few key parameters such as sensitivity, selectivity, image rejection, intercept point, and dynamic range. Unfortunately, this results in important key performance issues being overlooked. This paper looks at spurious responses in wide-coverage narrowband receivers that may be employed in sensor networks or for spectrum sensing in cognitive radio. A detailed measurement and graphical plot of all spurious responses from 100 kHz to 1 GHz is presented. This comprehensive assessment illustrates that receivers may show extensive false signal responses, even if they have relatively good classic specifications in areas such as selectivity and image rejection.