A BLOS-HF decision aid

A decision aid used to calculate signal coverage areas and signal interference regions in beyond line of sight (BLOS) high frequency (HF) communications systems is described. The interference and coverage capabilities of HF-BLOS communications systems are influenced by the ionospheric environment through which radio signals must propagate. A technique based on the tactical use of signal propagation which exploits knowledge of the ionosphere coupled with ray-tracing techniques may be used to minimise signal interference and maximise signal coverage. Such improvements are achieved without resorting to sophisticated systems techniques such as antenna nulling or coding. This paper investigates the tactical propagation technique via the development of a BLOS-HF frequency management decision aid. The decision aid employs an ionospheric environmental model and a communications model to predict both the interference and coverage of a HF communications link. Using these models the decision aid recommends system configurations (e.g. best frequency) which avoid known locations whilst maximising communications coverage.