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From: Greg Heath on 14 Jul 2010 08:18
On Jul 13, 9:32 am, "Wayne King" <wmkin...(a)gmail.com> wrote:
> Greg Heath <he...(a)alumni.brown.edu> wrote in message <6db36221-b4c2-4eb8-966d-3935c3a39...(a)g19g2000yqc.googlegroups.com>...
> > On Jul 13, 2:48 am, "Martijn Roelofsz" <martijn.roelo...(a)nlr.nl>
> > wrote:
> > > Greg, thanks for your reply. When I use your code I still get 4.6922 at 200Hz. I get read that number from the plot after zooming in on the 200Hz spike.
>
> > > It is just hard for me to understand that a 200Hz, 20mV top to top sine does not have a 10mv(or close to) outcome as fft.
>
> > 10*sin(z) = 5*exp(j*z)+5*exp(-j*z)
>
> > If you had an integral number of periods you
> > would get 5 instead of 4.6922.
>
> > Lothar: This is the result of "leakage"
>
> > The other 4.6922 is at frequency -200Hz+Fs.
>
> > Hope that helps.
>
> > Greg
>
> > Greg
>
> Hi Greg, just a minor typo, I think you meant:
>
> 10*cos(z) = 5*exp(j*z)+5*exp(-j*z)

Thanks.

The older I get, the more out of phase I become.

Greg
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