A technique is disclosed for detecting the presence of a certain form of tampering with respect to the operation of a location tracking device. The tracking device is of the kind that receives signals from which the location of the tracking device is determined and the tampering that is detected is of the kind wherein signal shielding material is placed around the device and/or a signal jamming device is used. In accordance with one aspect of the present invention, the location tracking device includes a metal detector whose output is processed to provide a shielding alarm signal. In accordance with another aspect of the present invention, the gain provided by the AGC circuit in the GPS or other wireless signal receiver within the location tracking device is processed to form a shielding alarm signal. These alarm signals may be distinct so as to distinguish between the different forms of tampering. In addition, either one of these described aspects may be used alone or in combination with one another.
