Intended signals and ambient electromagnetic noise in HF spectrum management

Both spectrum management - the organization of radio services in the spectrum to maximize spectrum utility - and radio link planning and the associated equipment design require a-priory knowledge of the electromagnetic environment. The dynamic range of the planned radio system must be able to support the accumulated power of intended radio signals within the bandwidth of the receiver front-end, and the ambient electromagnetic noise field strength must be accounted for in the link budget calculations. These items are especially important for sensitive receivers in the HF (3-30 MHz) frequency range, e.g. for radio astronomy or emergency communications. This paper will discuss these spectrum management and equipment design issues, with an emphasis on ambient electromagnetic noise.