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#19
November 11th 14, 02:08 AM
posted to rec.radio.amateur.antenna
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A short 160M antenna
On 11/10/2014 6:00 PM, Wimpie wrote:
El 10-11-14 19:39, escribió: wrote: snip Jim, I would encourage you to dive into rotating magnetic dipole radiation. You mean like in a pulsar? To be more precise, I mean the radiation with same frequency as pulsar rotation, of course only present when there is a net magnetic dipole moment. I am not pointing to the pulsed RF radiation. I want to be clear on this. You are saying that a rotating magnetic dipole *does* create EM waves just the same as any antenna? The only difference between a Pulsar and a handheld magnet is one of scale? For practical electromechanical systems (even in practial vacuo) it is negligible as (c0)^5 is in the denominator and (2*pi*rev/s)^4 is in the numerator, but that doesn't mean it isn't present from a theoretical point of view. Again, not talking about any "electromechanical system", just a permanet magnet spining. That just spinning magnet produces dB/dt, hence an E-field (not conservative). Superposition of two quadrature magnetic oscillating dipoles (small loop antnenas) gives a rotating magnetic dipole field. Such a quadrature setup can be exchanged by a rotating permanent magnet. Also implied is the macro level, i.e. a magnet one can hold in one's hand and velocities well below any relativisitc effects. I considered non-relativistic velocities only. I'm not interested in Jim's hand waving. Either a magnet can or can't generate EM waves. If a big one does it, then a little one does it too. -- Rick |
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