On Thu, 2007-05-31 at 21:45 -0400, Gary Hoffman wrote:
> That's right. A zero beat means that the two tones are identical and so
> their vector sum is zero. Hence no output. Unless of course one does
> something odd with the phase of the two signals. Is that being done here ?
>
> 73 de Gary, AA2IZ
>
To the contrary, when two signals are on exactly the same frequency the
need not be out of phase, they can have any relative phase angle and
when in phase they will add, when perfectly out of phase AND the same
amplitude they will cancel. When their frequencies differ slightly all
amplitudes will be heard from cancellation or near cancellation to
addition. When there is no perception of change of amplitude they they
are in perfect zero beat. If they go from peak through the near
cancellation back to peak in 1 second that's a frequency difference of 1
Hz which is good enough for most ham operations...
In graphic vector sums, think of it as one vector fixed with the second
vector's tail anchored to the head of the first vector and swinging
around that anchor at the difference frequency.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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