Abstract: 1. In a signal jamming device, first and second transducers physically displaced relative to each other said transducers having substantially identical signal coupling characteristics on the basis of direction to a selected distant object, means for coupling said transducers whereby signals received by one transducer are emitted by the other and vice versa, and differential impedance means connected to said means for coupling for producing phase shift of signals emitted by one transducer relative to signals emitted by the other transducer.