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## Re: [RFI] Electric company problem

 To: "RFI List" Re: [RFI] Electric company problem "Jim Brown" Sat, 10 Dec 2005 21:15:25 -0600
 ```On Sat, 10 Dec 2005 20:51:01 -0500, Tom Rauch wrote: >The noise >is sampled, phase inverted, and combined with the noise from >the main antenna at the same level as that noise. What you >are really doing is setting the sensitivity of the sense >antenna and main antenna to the same level at the distance >and angle of the undesired signal, and inverting the noise >exactly 180 degrees. I agree with almost everything you are saying with respect to cancellation of multiple sources and azimuth, except for one VERY important thing. A noise canceller is SHIFTING the phase of the noise sense antenna so that the resultant signal from the sense antenna is 180 degrees out of phase from that same noise on the main receiving antenna. That phase shift may be any number of degrees from -infinity to +infinity (although -180 to +180 is enough). :) The fact that it must be a phase SHIFT and not only a simple polarity reversal is what makes the adjustment so tricky (and why it must be re-balanced when the frequency changes very much). This is a discussion we have had before, and as a practitioner in both the audio and RF worlds, I am VERY bitchy about the difference between polarity and phase. I know you design these things, and that you do that very well, but the way we TALK about how they work is very important to all of us understanding them. :) Polarity is a two-valued function, and it is not related to frequency or time. Phase has an infinite number of values, and it IS a function of frequency and time. It is not possible to "invert the phase." 73, Jim K9YC _______________________________________________ RFI mailing list RFI@contesting.com http://lists.contesting.com/mailman/listinfo/rfi ```
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