Re: Sine wave frequency

On Sun, 11 Dec 2005 21:54:06 +0100, Paul Burridge wrote:

> On Sun, 11 Dec 2005 11:48:08 -0700, Don Lancaster <don@xxxxxxxxxx>
> wrote:
>
>>Mac wrote:
>>> On Sun, 11 Dec 2005 01:22:38 -0800, thejim wrote:
>>>
>>>
>>>>I wanted to ask if the sine wave can only have 1 frequency which is
>>>>standard or it can take the form of more than 1 frequency.
>>>
>>>
>>> The simple answer is that in popular usage a sine wave is only a single
>>> frequency.
>>>
>>> But in the real world there is always noise riding on that sine wave, and
>>> possibly other sine waves of smaller amplitude. So if you look at your
>>> sine wave on a spectrum analyzer, you will find that the peak is not a
>>> spike, such as you would see in a purely mathematical Fourier transform,
>>> but is spread out over some frequency range.
>>>
>>> You would also see that there are harmonics present. That is to say, there
>>> are components at 2x, or 3x or some higher integer multiple of the
>>> fundamental sine wave frequency.
>>>
>>> What made you think to ask this question here instead of, say,
>>> sci.electronics.basic?
>>>
>>> --Mac
>>>
>>A sinewave could only have a single frequency if it was on forever.
>>The switching envelope will otherwise interact with the sinewave itself.
>>
>>Which is what windowing is all about.
>
> People here seem to be forgetting it's a *pure* sine wave that
> constitutes a single frequency. Any form of ' irregular sine wave'
> will contain components of other frequencies and they may not be
> apparent from visual examination of the wave on an oscilloscope. Their
> presence undeniable, nevertheless.

Which people are you talking about? Maybe there are some posts which have
not appeared on my server yet?

<Checks google groups>

No, I don't see anyone who seems to be forgetting that.

--Mac

.

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