I asked a friend how capacitative coupling works in glass-mount antennas.
He said it's like when installing a sound system; where you want to keep the power & audio cables separated, to avoid electrical noise/interference.
I guess he was implying the plastic insulation behaves like a capacitor, effectively coupling two parallel circuits.
I'd originally assumed the noise was caused by the electromagnetic field radiating beyond the borders of the insulation, as opposed to via direct physical contact. But I thought to myself, "The cables aren't coiled. The current's direct. There's no inductance here." † And then I wondered if it even actually works like that. I always thought electricity implies electromagnetism, regardless; that anywhere an electric current or potential occurs, there's an inherent field of electromagnetic radiation, no matter how small.
So which is true? Is an inductor required to induce an electromagnetic field (ie. an electric current oscillating about a coil), or does a limited field already exist simply by virtue of the presence of electricity?
And by extension: Is all electronic/electrical wireless transmission technology (i.e. power and communications) made possible by virtue of induction? ‡
† A few things: a) We were referring to an automotive sound system with a 12V+ DC power supply. b) The speakers have coils. c) The audio signal could be considered AC.
‡ a) Sure; speech, music, sign language, smoke signals, etc. These are all technically wireless communication methods. b) Yes; you could perform photosynthesis or cellular-respiration, rub your hands together, or light a match with a laser-pointer and say it's wireless transmission of energy. c) But it's not a trick question, let's stick to man-made devices, and concepts like electricity and RF.