= Tuned spark wireless apparatus
<Guglielmo Marconi>'s 1909 lecture describes <antennas> with earth connections and separate coupled receiving circuits. His 1900 system coupled a closed <capacitor>–<inductor>–<spark gap> loop to a transmitting <antenna>. Coil spacing adjusted coupling; <inductance> and <capacitance> adjusted tuning. All four circuits were tuned together. By 1909 his company's stations mainly used magnetic receivers, rather than <coherers>.<Wireless Telegraphic Communication by Guglielmo Marconi>[1909 lecture, Figs. 2–3, 6 and 8 and associated paragraphs; receiver paragraph at Fig. 25]{ref}
Those are a participant's retrospective descriptions, not a complete account of priority. An earth connection is part of this <antenna> arrangement; it is not a universal requirement for <radio communication>. Nor does tuning an isolated <LC circuit> ensure that its <frequency> remains unchanged when strongly coupled to another circuit. The <coupled resonant circuit model> quantifies that distinction.
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