From rweber@cmu.edu Wed Feb 14 13:01:28 1996
Path: ashpoly!cascade!transat!eunet-de!hansebox!cmu!rweber
From: rweber@cmu.edu (Rodrigo Weber)
Newsgroups: comp.dsp
Subject: Data: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Feb14.130128.8220@cmu.edu>
Date: Wed, 14 Feb 1996 13:01:28 GMT
Organization: Carnegie Mellon University School of CS
NNTP-Posting-Host: cmu.edu
X-Newsreader: WinVN 0.99.5
Lines: 11

Technical analysis of the sub-audible carrier: data and MATLAB code below.

Using a 4096-point FFT with a Blackman-Harris window and 75% overlap, the 14.2 Hz peak is 42 dB below full scale.
With a 12th-order Burg AR model, the pole is located at z = 0.9992 * exp(j * 2 * pi * 14.2 / Fs).

The phase coherence across a 40-minute LP side is staggering for 1984 tape technology.

-- 
Rodrigo Weber
Opinions expressed are solely my own and not those of Carnegie Mellon University School of CS.
------------------------------------------------------------

From msantos@clari.net Wed Feb 14 19:20:28 1996
Path: ashpoly!cascade!brgate!saturno!clari!msantos
From: msantos@clari.net (Mikhail Santos)
Newsgroups: comp.dsp
Subject: Re: Data: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Feb14.192028.7343@clari.net>
Date: Wed, 14 Feb 1996 19:20:28 GMT
References: <1996Feb14.130128.8220@cmu.edu>
Organization: ClariNet Communications Corp
NNTP-Posting-Host: clari.net
X-Newsreader: NewsWatcher 2.0b24
Lines: 12

In article <1996Feb14.130128.8220@cmu.edu>, rweber@cmu.edu (Rodrigo Weber) writes:
> Technical analysis of the sub-audible carrier: data and MATLAB code below.
> Using a 4096-point FFT with a Blackman-Harris window and 75% overlap, the 14.2 Hz peak is 42 dB below full scale.

Have you checked your sound card's ADC clock? Cheap Sound Blaster cards use uncalibrated ceramic resonators that drift with temperature.

Unsubscribe me from this list! (Wait, this is Usenet, never mind).

-- 
Mikhail Santos | msantos@clari.net
PGP Key fingerprint: CB0C 819F 3B75 DCBD
"Keep the channels open."

From mrodriguez@pipeline.com Fri Feb 16 12:53:28 1996
Path: ashpoly!cascade!transat!eunet-fr!teletel!pipeline!mrodriguez
From: mrodriguez@pipeline.com (Mateo Rodríguez)
Newsgroups: comp.dsp
Subject: Re: Data: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Feb16.125328.4275@pipeline.com>
Date: Fri, 16 Feb 1996 12:53:28 GMT
References: <1996Feb14.130128.8220@cmu.edu> <1996Feb14.192028.7343@clari.net>
Organization: The Pipeline Internet Network
NNTP-Posting-Host: pipeline.com
X-Newsreader: NewsWatcher 2.0b24
Lines: 9

In article <1996Feb14.192028.7343@clari.net>, msantos@clari.net (Mikhail Santos) writes:
> Have you checked your sound card's ADC clock? Cheap Sound Blaster cards use uncalibrated ceramic resonators that drift with temperature.

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

-- 
Mateo Rodríguez | mrodriguez@pipeline.com
PGP Key fingerprint: 9360 2D28 99F7 0EAB
"Keep the channels open."

From mrobertson@mindspring.com Sat Feb 17 09:39:28 1996
Path: ashpoly!cascade!mxgate!coyoacan!mindspring!mrobertson
From: mrobertson@mindspring.com (Mateo Robertson)
Newsgroups: comp.dsp
Subject: Re: Data: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Feb17.093928.5880@mindspring.com>
Date: Sat, 17 Feb 1996 09:39:28 GMT
References: <1996Feb14.130128.8220@cmu.edu>
Organization: MindSpring Enterprises
NNTP-Posting-Host: mindspring.com
X-Newsreader: TIN [version 1.2 PL2]
Lines: 9

In article <1996Feb14.130128.8220@cmu.edu>, rweber@cmu.edu (Rodrigo Weber) writes:
> Technical analysis of the sub-audible carrier: data and MATLAB code below.

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

-- 
=== Mateo Robertson ===
Dept of Electrical Engineering, MindSpring Enterprises
"5 sigma is a discovery. 7 is a question."