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Re: [Discuss-gnuradio] Doppler shift on waterfall plot with audio signal

From: Ellis, Duane
Subject: Re: [Discuss-gnuradio] Doppler shift on waterfall plot with audio signal
Date: Fri, 21 Oct 2016 21:46:05 +0000

steve> I don't observe any doppler shift when I move my hand/walk in the 
steve>> I can see the FFT plots change in shape on motion, but nothing is 
steve>> observed on the Waterfall sink.

If you want to see this, a QAM or BPSK constellation plot would be a better 

Have you gone through the math? What frequency change/shift are you expecting 
(mathematically) to see?

Here's an example from Georgia State University that explains the math.

This screen does the math for you (just plug in numbers)

At 25C (77F) - a 440hz sound (the classic "A" sound) - 
With a 1 meter per second motion (speed of your hand waving) you see a +1.27hz 
increase approaching

A 10% change in frequency requires almost 30 meter/sec (aka: 67 miles per hour)

What is the scale/range of your waterfall graph? 
Given that scale - Would a 40hz change be visible?


As an aside...

Clifford Stolls TED talk Video talks about this indirectly 
He's using a microphone + oscilloscope - to display the audio wave form.



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