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Re: [Discuss-gnuradio] An interesting application for my new USRP... som

From: John Ackermann N8UR
Subject: Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested
Date: Thu, 26 May 2005 16:05:41 -0400
User-agent: Mozilla Thunderbird 1.0 (Windows/20041206)

Larry Doolittle wrote:

I think the FFT-based analysis is less than ideal.  You really want
to track the phase, count cycles, and measure the phase difference
over a defined time.  delta(phase)/delta(time) is the average frequency.
Your phase error could be as small as a few milliradians, and you said
the integration time is at least 10 minutes: your measurement error could
approach a micro-Hertz, if your reference oscillator were perfect.

uHertz are nice. :-)

I guess the reason I've been fixated on an FFT is that the signal I'm looking for won't be the only one there -- there will be noise (natural and man0made), fading, and probably other signals within a few tens of Hz of the desired signal, so I've been visualizing an FFT with audio demod as the way to spot the signal I'm looking for in post-processing. Once I have it spotted, of course, I could then apply other techniques.


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