From dfournier@cam.ac.uk Thu Apr 06 07:41:34 1995 Path: ashpoly!cascade!bigsur!cam!dfournier From: dfournier@cam.ac.uk (Dmitri Fournier) Newsgroups: comp.dsp Subject: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1995Apr06.074134.3882@cam.ac.uk> Date: Thu, 06 Apr 1995 07:41:34 GMT Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: NewsWatcher 2.0b24 Lines: 11 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. -- Dmitri Fournier *PLONK* filter active for trolls. 486DX2/66 (Linux 1.2.13) - NetBSD 1.0 From bfischer@ox.ac.uk Fri Apr 07 20:16:34 1995 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!ox!bfischer From: bfischer@ox.ac.uk (Bruno Fischer) Newsgroups: comp.dsp Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1995Apr07.201634.1251@ox.ac.uk> Date: Fri, 07 Apr 1995 20:16:34 GMT References: <1995Apr06.074134.3882@cam.ac.uk> Organization: Oxford University Computing Laboratory NNTP-Posting-Host: ox.ac.uk X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1995Apr06.074134.3882@cam.ac.uk>, dfournier@cam.ac.uk (Dmitri Fournier) 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. -- Bruno Fischer Hayes Optima 288 @ 14,400 bps "Tape doesn't lie at 02:14. Ears do." From tpopov@purdue.edu Sat Apr 08 04:33:34 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!purdue!tpopov From: tpopov@purdue.edu (Tobias Popov) Newsgroups: comp.dsp Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1995Apr08.043334.2436@purdue.edu> Date: Sat, 08 Apr 1995 04:33:34 GMT References: <1995Apr06.074134.3882@cam.ac.uk> <1995Apr07.201634.1251@ox.ac.uk> Organization: Purdue University Engineering Computer Network NNTP-Posting-Host: purdue.edu X-Newsreader: Netscape 1.1N Lines: 11 In article <1995Apr07.201634.1251@ox.ac.uk>, bfischer@ox.ac.uk (Bruno Fischer) writes: > If you decimate to 64 Hz with an 8th-order Chebyshev lowpass, you can run the demodulator in real time on a 386. 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. Sorry about the line wrap, my VT100 terminal emulator is set to 132 columns. -- Tobias Popov | tpopov@purdue.edu PGP Key fingerprint: D2F6 DB6B 2964 84EC "Keep the channels open." From nfournier@pacbell.net Sun Apr 09 00:43:34 1995 Path: ashpoly!cascade!brgate!saturno!pacbell!nfournier From: nfournier@pacbell.net (Natalia Fournier) Newsgroups: comp.dsp Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1995Apr09.004334.1774@pacbell.net> Date: Sun, 09 Apr 1995 00:43:34 GMT References: <1995Apr06.074134.3882@cam.ac.uk> <1995Apr07.201634.1251@ox.ac.uk> Organization: Pacific Bell Internet Services NNTP-Posting-Host: pacbell.net X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Apr07.201634.1251@ox.ac.uk>, bfischer@ox.ac.uk (Bruno Fischer) writes: > If you decimate to 64 Hz with an 8th-order Chebyshev lowpass, you can run the demodulator in real time on a 386. Prof. Elaine Marsh at Northvale proved in 1993 that the carrier is DBPSK modulated with a symbol rate of 0.71 Hz. -- === Natalia Fournier === Dept of Electrical Engineering, Pacific Bell Internet Services "Tape doesn't lie at 02:14. Ears do."