Radio atmospheric km. For ELF waves (< 3 kHz), ray theory becomes invalid, and only mode theory is appropriate. Here, the zeroth mode begins to dominate and is responsible for the second window at greater distances. Resonant waves of this zeroth mode can be excited in the Earth–ionosphere waveguide cavity, mainly by the continuing current components of lightning flowing between two return strokes. Their wavelengths are integral fractions of the Earth's circumference, and their resonance frequencies can thus be approximately determined by "f" ≃ "mc"/(2π"a") ≃ 7.5 "m" Hz (with "m" = 1, 2, ...; "a" the Earth's radius and "c" the
Waves Radio In addition to these, a weekly news magazine programme, Making Waves, is broadcast on Sunday evenings from 6.00pm - 7.00pm. The Sportsdesk, a daily round up of sports news, is broadcast at 5.20pm on weekdays. On Saturday afternoons scores and results are updated from 2-6pm on the Sportsmix. 1. History Waves Radio Waves Radio is a local radio station based in Peterhead, North East Scotland. The station is on air 24 hours a day with live shows from 6am till 10pm (apart from "a wave of hits" from 6pm-7pm on weekdays which is automated). Waves Radio was born in 1990