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| Why evolution by natural selection didn't make use of RF? |
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| coppercone2:
some how derailing this thread to yell about harmonics is just not cool |
| Bud:
--- Quote from: RoGeorge on August 31, 2023, 04:47:32 pm --- For example, if we take a square wave of 1kHz, such a signal is supposed to have plenty of sinusoidal 3kHz in it, according to Fourier. However, one can make a filter that will only respond to a sinusoidal shape of 3kHz, and no other shape than sinusoidal. --- End quote --- No, one cannot :-DD |
| tggzzz:
--- Quote from: Bud on September 01, 2023, 03:29:31 am --- --- Quote from: RoGeorge on August 31, 2023, 04:47:32 pm --- For example, if we take a square wave of 1kHz, such a signal is supposed to have plenty of sinusoidal 3kHz in it, according to Fourier. However, one can make a filter that will only respond to a sinusoidal shape of 3kHz, and no other shape than sinusoidal. --- End quote --- No, one cannot :-DD --- End quote --- How about capturing the signal, doing an FFT, and seeing if there is any frequency other than 3kHz :) Oops; that contains the "invalid" word "Fourier". Or an analogue variant: a bandstop filter centered on 3kHz, plus a switch. If the filter's output is non-zero, the switch is opened. Oops; that depends on the concept of the equivalence of time and frequency domains, as defined by Fourier. |
| Bud:
--- Quote from: RoGeorge on August 31, 2023, 04:47:32 pm ---Such a 3kHz filter won't respond to a square wave of 1kHz, which indicates there is no sinusoidal 3kHz in our 1kHz square. I'll say that's a proof Fourier spectrum is not really there. --- End quote --- That is exactly what a 3kHz filter WILL DO, you just have not tried or have not measured properly. |
| coppice:
Its sad how many of the messages in this thread come down to "that can't happen. because I've never seen it happen", rather than "here is a physics road blocker which means that can't happen". |
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