Antenna's question

  • Thread starter derek10
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To avoid derailing this thread, I will post a new one. Here's the discussion context.

Your question is fundamentally flawed, I'm afraid because it's harder than that, in fact. Photons do not 'have a wavelength'. They are not classical particles but quantum entities. What you 'are allowed' to say is that the EM wave they are associated with, has a wavelength. There is no fundamental maximum for wavelength but EM at very low frequencies has very low energy photons and becomes harder and harder to detect because you just can't make receiving equipment that can 'extract' the signal out of the space it's travelling through. (The antenna would have to be several thousand km long to intercept a 50Hz signal)
why can battery-operated amplifiers and oscilloscopes pick up the mains noise (50 Hz in Europe) when you touch the input cable?
Because the em wave is not a 'launched wave, travelling free through space but guided on the wire. To launch a significant level of signal into space. from a circuit, it has to be 'matched', which requires a radiating structure that's not much smaller than one wavelength. A wire / person link is a totally different situation.
Thanks

Consider this case:
Battery operated amplifier (isolated from mains)
Person, which is isolated from mains (not touching anything except the amplifier input,)

when the person touches the amplifier input, it will buzz at 50Hz (tested myself), I though it was because the home wires acting like a emitter antenna, the person as a receiver antenna, and the finger touching it like a cable, but the highlighted Sophiecentaur's comment confused me. Is this phenomenon caused by a different mechanism? Is it because the person organs, skin, blood vessels, etc sum up to enormous lengths (I read up to 60000 miles) and making an antenna? Is capacitive/inductive coupling possible in these circumstances?

Thank you :)
 
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CWatters
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The human body is not a very good antenna at 50Hz. It's due to capacitance between the mains wiring and the body.
 
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The human body is not a very good antenna at 50Hz. It's due to capacitance between the mains wiring and the body.
Thank you, that's what I suspected: wires and person are plates and the space between form the capacitor
 

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