From periksson@pacbell.net Wed May 17 07:25:48 1995
Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!pacbell!periksson
From: periksson@pacbell.net (Pavel Eriksson)
Newsgroups: comp.dsp
Subject: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1995May17.072548.1014@pacbell.net>
Date: Wed, 17 May 1995 07:25:48 GMT
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Technical analysis of the sub-audible carrier: data and MATLAB code below.

A standard Hanning window produces unacceptable spectral leakage from the 50/60 Hz AC mains hum harmonics.
Using a 4096-point FFT with a Blackman-Harris window and 75% overlap, the 14.2 Hz peak is 42 dB below full scale.

I've uploaded the C source for my decimation and bandpass filter to ftp.ashford-poly.edu.

-- 
=== Pavel Eriksson ===
Dept of Electrical Engineering, Pacific Bell Internet Services
"Extraordinary claims require extraordinary spectra."

From tsato@panix.com Wed May 17 14:19:48 1995
Path: ashpoly!cascade!transat!eunet-de!hansebox!panix!tsato
From: tsato@panix.com (Tyler Sato)
Newsgroups: comp.dsp
Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1995May17.141948.5363@panix.com>
Date: Wed, 17 May 1995 14:19:48 GMT
References: <1995May17.072548.1014@pacbell.net>
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In article <1995May17.072548.1014@pacbell.net>, periksson@pacbell.net (Pavel Eriksson) writes:
> Technical analysis of the sub-audible carrier: data and MATLAB code below.

Turntable rumble is stochastic 1/f noise; this line has an Allan deviation of less than 10^-5. It was generated by a quartz crystal clock.

-- 
Tyler Sato
Opinions expressed are solely my own and not those of Public Access Unix of New York.
------------------------------------------------------------

From ktakahashi@uni-hamburg.de Fri May 19 08:52:48 1995
Path: ashpoly!cascade!bigsur!uni-hamburg!ktakahashi
From: ktakahashi@uni-hamburg.de (Karen Takahashi)
Newsgroups: comp.dsp
Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1995May19.085248.5228@uni-hamburg.de>
Date: Fri, 19 May 1995 08:52:48 GMT
References: <1995May17.072548.1014@pacbell.net>
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In article <1995May17.072548.1014@pacbell.net>, periksson@pacbell.net (Pavel Eriksson) writes:
> Technical analysis of the sub-audible carrier: data and MATLAB code below.

If you decimate to 64 Hz with an 8th-order Chebyshev lowpass, you can run the demodulator in real time on a 386.

-- 
Karen Takahashi
Tape trading list upon request. SASE required for international mail.

From icampbell@uni-hamburg.de Sun May 21 00:44:48 1995
Path: ashpoly!cascade!transat!sunet!nordrelay!uni-hamburg!icampbell
From: icampbell@uni-hamburg.de (Ines Campbell)
Newsgroups: comp.dsp
Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1995May21.004448.6054@uni-hamburg.de>
Date: Sun, 21 May 1995 00:44:48 GMT
References: <1995May17.072548.1014@pacbell.net>
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In article <1995May17.072548.1014@pacbell.net>, periksson@pacbell.net (Pavel Eriksson) writes:
> Technical analysis of the sub-audible carrier: data and MATLAB code below.

Good work on the windowing. I replicated your result with an 8192-point FFT on a SPARCstation 20. The peak is exactly 14.2003 Hz.

-- 
=== Ines Campbell ===
Dept of Electrical Engineering, Universität Hamburg Fachbereich Informatik
"Measuring a record you own is listening, not piracy."

From ttanaka@cern.ch Tue May 23 04:03:48 1995
Path: ashpoly!cascade!mxgate!coyoacan!cern!ttanaka
From: ttanaka@cern.ch (Tobias Tanaka)
Newsgroups: comp.dsp
Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1995May23.040348.6331@cern.ch>
Date: Tue, 23 May 1995 04:03:48 GMT
References: <1995May17.072548.1014@pacbell.net> <1995May21.004448.6054@uni-hamburg.de>
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In article <1995May21.004448.6054@uni-hamburg.de>, icampbell@uni-hamburg.de (Ines Campbell) writes:
> Good work on the windowing. I replicated your result with an 8192-point FFT on a SPARCstation 20. The peak is exactly 14.2003 Hz.

Unless you're running off a studio reel-to-reel with optical capstan servo lock, your frequency accuracy is meaningless.

-- 
Tobias Tanaka
Tape trading list upon request. SASE required for international mail.