Propagation of signals in the frequency band between 30 MHz and 100 MHz

Propagation in the LoVHF (30 to 100 MHz) frequency band possesses characteristics common to both HF (3 to 30 MHz) and HiVHF (100 to 300 MHz) propagation. It is this feature which makes this frequency band both interesting and complex. The primary interest of this report is the modes of propagation between surface- or near-surface-based transmitters and receivers. For a given range, the strength, geographical and temporal dependence, and likelihood of a particular mode of propagation will be discussed. In the last section, various existing models that could be used to describe the field strength and transmission loss in the LoVHF band are assessed. These models and the discussion of the various modes of propagation fall roughly into two groups: (1) those that affect ranges less than 500 km, and (2) those that affect ranges greater than 500 km.