Abstract: Tactical radio navigation systems provide bearing information to an interrogating aircraft in response to pairs of interrogation pulses received at a beacon transponder, such systems also provide distance measuring and identification information. To provide the required bearing information, pulses radiated from a central antenna array are modulated at a 15 Hz frequency and by a 135 Hz frequency, by reflector elements rotating around a stationary central radiator. A counterpoise system associated with the central radiator and the reflector elements uptilts the carrier frequency and the 15 Hz modulation. To provide more uptilt to the radiated signal and further decrease the total energy radiated below the horizon, a double circuit shield counterpoise is provided in the lower part of a radome assembly enclosing the antenna system.

Abstract: Tactical radio navigation systems provide bearing information to an interrogating aircraft in response to pairs of interrogation pulses received at a beacon transponder, the system also provides distance measuring and identification information. To provide the required bearing information, pulses radiated from the central antenna array are modulated at a 15 Hz frequency and by 135 Hz frequency, by parasitic elements rotating around a stationary central array. Broadband operation of the system is provided by a distribution pattern of the 135 Hz parasitic elements mounted radially from the central antenna array on a dielectric disc. Nine groups of radially displaced 135 Hz elements are circumferentially arranged around the dielectric disc and each element of a group is tailored to a particular frequency band in the frequency spectrum allotted to radio navigation systems.