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I0OJJ > ANTENN 01.07.10 16:25l 42 Lines 1702 Bytes #-5798 (0) @ WW
BID : 6912I0OJJ
Read: GUEST DL8BO
Subj: Re: what happens to reflected energy ?
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On Jul 1, 12:37=A0pm, Cecil Moore <w5...@hotmail.com> wrote:
> On Jun 30, 11:29=A0am, Keith Dysart <keith.dys...@gmail.com> wrote:
>
> > Check the a0 coefficient in the Fourier transform. This represents
> > the DC component of the signal.
>
> And the result is zero EM waves, either forward or reflected, and your
> argument falls apart.
>
> > Without this, how would you deal with a signal such as
> > =A0 V(t) =3D 10 + 2 cos(3t)
>
> If the cosine term is zero, there are zero EM waves, either forward or
> reflected, and your argument falls apart.
>
> Incidentally, V(t) =3D 10, is a perfect way to prove that energy and the
> time derivitive of energy are not the same thing and your argument
> falls apart.
>
> > Alternatively, one can use the standard trick for dealing with
> > non-repetitive waveforms: choose an arbitrary period. 24 hours
> > would probably be suitable for these examples and transform from
> > there. Still, you will have zero frequency component to deal
> > with, but there will be some at higher frequencies (if you
> > choose your function to make it so).
>
> Windowing doesn't generate EM waves where none exist in reality and
> your argument falls apart.
> --
> 73, Cecil, w5dxp.com
a better argument is that a constant voltage produces a constant
electric field everywhere, since the field is not varying in time or
space there is no time or space derivative to create a magnetic field
so there can be no propagating em wave. you could do the same with
zero or constant current producing a constant magnetic field.
essentially the dc case IS unique in that you must wait forever for it
to reach sinusoidal steady state since the lowest frequency component
is 0hz.
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