A Step-Frequency Pulse Experiment with High-frequency Antipodal and Circulating Signals

Abstract

NUMEROUS experiments have been conducted during the past four decades to determine the characteristics of round-the-world short-wave radio signals and their relationship to world-wide ionospheric conditions. Such echoes have been received over transmitter-receiver paths of up to 10,000 kilometres in length, the radio pulses presumably passing on about the world to arrive at the receiving site approximately 138 milliseconds (ms) later than the direct signal. Closely linked to the round-the-world investigations is the question of antipodal effects; that is, the geometric focusing of short-wave radio signals by the ionosphere at a point diametrically opposite to a transmitter on the Earth's surface. First postulated by Marconi¹, antipodal transmissions have been investigated at certain discrete frequencies by several investigators^2–4. However, to our knowledge, synchronized step frequency soundings previously have not been conducted between antipodal transmitter and receiver sites.