Null Direction Propagation of Antennas and Counter Measures in Tactical High Frequency Sky Wave Communication
In tactical High Frequency (HF) communication, sky wave and ground wave mode establish the radio link. There is a phenomenon by which antenna in ground wave mode communicates with antenna in sky wave mode. This happens due to emission of radio waves in the NULL direction. This emission can be an unintended transmission, thus can be intercepted and used by the insurgents against armed forces. Also the same can considered for the friendly communication, thus removing the skip zone. This paper describes the study of Null direction propagation of HF antenna and proposes the counter measures for the same.