Understanding VHF (Very High Frequency) Propagation

More Information

VHF frequencies (30–300 MHz) support broadcasting, voice communications, aviation navigation, and defense radar. Yet VHF propagation is widely misunderstood. The common assumption of “line of sight” oversimplifies how signals behave in practice. In terrestrial environments, VHF signals interact with the atmosphere and physical objects continuously. Refraction in the troposphere bends signals beyond the geometric horizon. Reflections from buildings and terrain create multipath interference. Diffraction carries signals into shadow zones behind obstacles. Beyond these everyday effects, several uncommon modes can extend VHF range dramatically. Tropospheric ducts formed by temperature inversions can channel signals over 1,500 km. Sporadic E events create temporary ionospheric patches reflecting lower VHF signals up to 2,500 km. Meteor ionization trails offer brief but reliable reflectors for data telemetry. EME (Earth-Moon-Earth) communication uses the moon as a passive reflector for worldwide coverage. This white paper covers the physics, practical characteristics, and operational significance of each mode. It equips engineers and planners with the knowledge needed for effective VHF system design.