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Re: [Discuss-gnuradio] WWVB demodulator

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] WWVB demodulator
Date: Sun, 26 Dec 2010 22:24:38 -0500
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On 12/26/2010 09:54 PM, Michael Ossmann wrote:

I started to years ago but never got very far.  It looked like
starting with goertzel was going to work.  I think I planned to dump
goertzel output into M&M clock recovery with a 10 Hz symbol rate and
then count the number of .1 second chunks per pulse.


I'm not too worried about computational efficiency, so I hadn't considered Goertzel. My current approach (that I've just developed this evening :-) ), is to assume a 192KHz sound card input (which is congruent with the approach I'm currently using for VLF signal processing for ionospheric measurements), bandpass filter at 60KHz (+/- 100Hz), then detect the result and data slice into 1s and 0s at 10Hz--the data slicing is driven by computing a longer-term signal level average (since WWVB basically uses ON/OFF (well ON, and 10dB down)

Having a variable that tracks the medium-term average allows the receiver to track fading and tweak the data slicer

Haven't decided how I'll turn the PWM into actual 1s and 0s yet.

Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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