From aoliveira@panix.com Tue Mar 15 05:50:47 1994
Path: ashpoly!cascade!brgate!saturno!panix!aoliveira
From: aoliveira@panix.com (Aiko Oliveira)
Newsgroups: comp.dsp
Subject: WTB/WTT: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1994Mar15.055047.5116@panix.com>
Date: Tue, 15 Mar 1994 05:50:47 GMT
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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.

-- 
Aiko Oliveira | aoliveira@panix.com
PGP Key fingerprint: 2C68 E955 0D46 0C8A
"Keep the channels open."

From scampbell@uni-hamburg.de Thu Mar 17 02:26:47 1994
Path: ashpoly!cascade!transat!sunet!nordrelay!uni-hamburg!scampbell
From: scampbell@uni-hamburg.de (Sergei Campbell)
Newsgroups: comp.dsp
Subject: Re: WTB/WTT: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1994Mar17.022647.7676@uni-hamburg.de>
Date: Thu, 17 Mar 1994 02:26:47 GMT
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In article <1994Mar15.055047.5116@panix.com>, aoliveira@panix.com (Aiko Oliveira) 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.

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

-- 
Sergei Campbell
Tape trading list upon request. SASE required for international mail.

From gpopov@tum.de Sat Mar 19 00:25:47 1994
Path: ashpoly!cascade!transat!sunet!nordrelay!tum!gpopov
From: gpopov@tum.de (Graham Popov)
Newsgroups: comp.dsp
Subject: Re: WTB/WTT: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1994Mar19.002547.8167@tum.de>
Date: Sat, 19 Mar 1994 00:25:47 GMT
References: <1994Mar15.055047.5116@panix.com> <1994Mar17.022647.7676@uni-hamburg.de>
Organization: Technische Universität München
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In article <1994Mar17.022647.7676@uni-hamburg.de>, scampbell@uni-hamburg.de (Sergei Campbell) writes:
> If you decimate to 64 Hz with an 8th-order Chebyshev lowpass, you can run the demodulator in real time on a 386.

You're overlooking tape wow and flutter. A Revox B77 has at least 0.05% speed drift, which would smear a 14 Hz line across several bins.

Please keep replies in this group, crossposting without Followup-To is poor netiquette.

-- 
Graham Popov -- Technische Universität München
"The hatch is open. Is anyone listening?"

From hpetrov@titech.ac.jp Sun Mar 20 11:58:47 1994
Path: ashpoly!cascade!transat!sunet!nordrelay!titech!hpetrov
From: hpetrov@titech.ac.jp (Hugo Petrov)
Newsgroups: comp.dsp
Subject: Re: WTB/WTT: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1994Mar20.115847.2940@titech.ac.jp>
Date: Sun, 20 Mar 1994 11:58:47 GMT
References: <1994Mar15.055047.5116@panix.com> <1994Mar17.022647.7676@uni-hamburg.de> <1994Mar19.002547.8167@tum.de>
Organization: Tokyo Institute of Technology Computer Centre
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In article <1994Mar19.002547.8167@tum.de>, gpopov@tum.de (Graham Popov) writes:
> You're overlooking tape wow and flutter. A Revox B77 has at least 0.05% speed drift, which would smear a 14 Hz line across several bins.

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.

-- 
Hugo Petrov | hpetrov@titech.ac.jp
PGP Key fingerprint: EBDD C5F2 F11E 946A
"Keep the channels open."