Avionics navigation systems for direction measurements have airborne receivers and ground transmitters, which are very expensive equipment. The training of pilots, engineers and technical staffs requires special installation of real equipment with the cooperation of both airborne and ground parts, or it is done through the aircraft simulation system which is special for each aircraft type. These techniques give only the global function training without any details of system hardware or signal processing. This work introduces a digital simulation for some avionics navigation systems of direction measurements as ADF (automatic direction finder) and TACAN (tactical air navigation) for training purposes covering : the system function, the essential processing steps, and the necessary test points. The simulated systems are interfaced with PC to control different modes of operations, and perform the necessary computations for the navigation process. The trainer is implemented using available ICs in the local market, tested, and used as an educational aid for avionics engineering students. It has the flexibility to add other new subsystems. It is of very-low cost when compared with other training facilities. The usual direct step-by-step analog simulation technique is complicated and requires special and expensive ICs as analog multipliers and mixers. The main idea behind this low-cost solution is the application of a versatile function generation using stored digital data and digital to analog conversion. Even the problem of AM (amplitude modulation) simulation process is solved using digital technique.