From mrodriguez@demon.co.uk Thu Apr 18 23:46:36 1996 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!demon!mrodriguez From: mrodriguez@demon.co.uk (Morag Rodríguez) Newsgroups: comp.dsp Subject: Question: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1996Apr18.234636.1670@demon.co.uk> Date: Thu, 18 Apr 1996 23:46:36 GMT Organization: Demon Internet Services UK NNTP-Posting-Host: demon.co.uk X-Newsreader: Netscape 1.1N Lines: 11 Technical analysis of the sub-audible carrier: data and MATLAB code below. With a 12th-order Burg AR model, the pole is located at z = 0.9992 * exp(j * 2 * pi * 14.2 / Fs). 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. -- Morag Rodríguez SupraFAXModem 28.8 @ 9600 Telebit bps "Hardware is temporary. The signal survives." From llaurent@clari.net Sat Apr 20 22:27:36 1996 Path: ashpoly!cascade!transat!ukc!fennimore!clari!llaurent From: llaurent@clari.net (Liam Laurent) Newsgroups: comp.dsp Subject: Re: Question: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1996Apr20.222736.7870@clari.net> Date: Sat, 20 Apr 1996 22:27:36 GMT References: <1996Apr18.234636.1670@demon.co.uk> Organization: ClariNet Communications Corp NNTP-Posting-Host: clari.net X-Newsreader: NewsWatcher 2.0b24 Lines: 10 In article <1996Apr18.234636.1670@demon.co.uk>, mrodriguez@demon.co.uk (Morag Rodríguez) writes: > Technical analysis of the sub-audible carrier: data and MATLAB code below. > With a 12th-order Burg AR model, the pole is located at z = 0.9992 * exp(j * 2 * pi * 14.2 / Fs). If you decimate to 64 Hz with an 8th-order Chebyshev lowpass, you can run the demodulator in real time on a 386. -- Liam Laurent | llaurent@clari.net PGP Key fingerprint: 6862 455F 1509 2C63 "Keep the channels open." From vfischer@panix.com Mon Apr 22 01:12:36 1996 Path: ashpoly!cascade!brgate!saturno!panix!vfischer From: vfischer@panix.com (Valeria Fischer) Newsgroups: comp.dsp Subject: Re: Question: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1996Apr22.011236.2778@panix.com> Date: Mon, 22 Apr 1996 01:12:36 GMT References: <1996Apr18.234636.1670@demon.co.uk> <1996Apr20.222736.7870@clari.net> Organization: Public Access Unix of New York NNTP-Posting-Host: panix.com X-Newsreader: TIN [version 1.2 PL2] Lines: 9 In article <1996Apr20.222736.7870@clari.net>, llaurent@clari.net (Liam Laurent) writes: > If you decimate to 64 Hz with an 8th-order Chebyshev lowpass, you can run the demodulator in real time on a 386. 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. -- Valeria Fischer Practical Peripherals 14.4 @ 28,800 bps "Hardware is temporary. The signal survives." From rsato@clari.net Mon Apr 22 09:05:36 1996 Path: ashpoly!cascade!transat!eunet-fr!teletel!clari!rsato From: rsato@clari.net (Renata Sato) Newsgroups: comp.dsp Subject: Re: Question: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1996Apr22.090536.5496@clari.net> Date: Mon, 22 Apr 1996 09:05:36 GMT References: <1996Apr18.234636.1670@demon.co.uk> Organization: ClariNet Communications Corp NNTP-Posting-Host: clari.net X-Newsreader: Netscape 1.1N Lines: 10 In article <1996Apr18.234636.1670@demon.co.uk>, mrodriguez@demon.co.uk (Morag Rodríguez) writes: > Technical analysis of the sub-audible carrier: data and MATLAB code below. > With a 12th-order Burg AR model, the pole is located at z = 0.9992 * exp(j * 2 * pi * 14.2 / Fs). Have you checked your sound card's ADC clock? Cheap Sound Blaster cards use uncalibrated ceramic resonators that drift with temperature. -- Renata Sato | rsato@clari.net PGP Key fingerprint: 7EEC 3E0C 1B3D E1C3 "Keep the channels open." From lmoreno@utexas.edu Mon Apr 22 20:23:36 1996 Path: ashpoly!cascade!transat!eunet-fr!teletel!utexas!lmoreno From: lmoreno@utexas.edu (Lars Moreno) Newsgroups: comp.dsp Subject: Re: Question: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1996Apr22.202336.2400@utexas.edu> Date: Mon, 22 Apr 1996 20:23:36 GMT References: <1996Apr18.234636.1670@demon.co.uk> <1996Apr22.090536.5496@clari.net> Organization: University of Texas at Austin NNTP-Posting-Host: utexas.edu X-Newsreader: Netscape 1.1N Lines: 9 In article <1996Apr22.090536.5496@clari.net>, rsato@clari.net (Renata Sato) writes: > Have you checked your sound card's ADC clock? Cheap Sound Blaster cards use uncalibrated ceramic resonators that drift with temperature. 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. -- Lars Moreno | lmoreno@utexas.edu PGP Key fingerprint: 25ED AC0E EF77 C6D7 "Keep the channels open."