You are confusing two usages of "out of phase":
1. having 180 degrees (pi radians) phase difference
2. not being in phase -- having a phase relationship of anything
other than zero phase difference
As Jerry said adding two signals that are precisely 180 degrees phase
difference will result in a zero amplitude signal. Adding two signals
with a random phase relationship will result in a higher amplitude
signal.
The latter case is "always" the case unless you have the two tones
both phase-locked. Which you won't have in tuning two separate
oscillators. Their phases will be just randomly related.
When you zero beat something you are going for zero frequency
difference between the tones -- the audible beat signal goes to zero
FREQUENCY not zero amplitude sum tone.
On May 31, 2007, at 7:33 PM, Gary Hoffman wrote:
That's what I said Jerry....or at least tried to say. Normally, in
applications I have experience with the signals are out of phase
and thus
cancel. This, in my personal view, is the most useful
configuration. But,
as I said, if someone does something else with the phase (i.e., in
phase
instead of out for instance) then they could add.
--
Kevin Purcell
kevinpurcell@pobox.com
|