From trodriguez@pipeline.com Wed Sep 27 10:10:01 1995 Path: ashpoly!cascade!mxgate!coyoacan!pipeline!trodriguez From: trodriguez@pipeline.com (Tyler Rodríguez) Newsgroups: comp.dsp Subject: Discussion: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1995Sep27.101001.4744@pipeline.com> Date: Wed, 27 Sep 1995 10:10:01 GMT Organization: The Pipeline Internet Network NNTP-Posting-Host: pipeline.com 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. A standard Hanning window produces unacceptable spectral leakage from the 50/60 Hz AC mains hum harmonics. I've uploaded the C source for my decimation and bandpass filter to ftp.ashford-poly.edu. -- Tyler Rodríguez *PLONK* filter active for trolls. Atari TT030 - NetBSD 1.0 From smoreno@uni-hamburg.de Wed Sep 27 18:00:01 1995 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!uni-hamburg!smoreno From: smoreno@uni-hamburg.de (Sergei Moreno) Newsgroups: comp.dsp Subject: Re: Discussion: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1995Sep27.180001.2993@uni-hamburg.de> Date: Wed, 27 Sep 1995 18:00:01 GMT References: <1995Sep27.101001.4744@pipeline.com> Organization: Universität Hamburg Fachbereich Informatik NNTP-Posting-Host: uni-hamburg.de X-Newsreader: WinVN 0.99.5 Lines: 10 In article <1995Sep27.101001.4744@pipeline.com>, trodriguez@pipeline.com (Tyler Rodríguez) 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 Moreno US Robotics Courier V.34 @ 28,800 bps "Measuring a record you own is listening, not piracy." From mbrennan@ox.ac.uk Wed Sep 27 19:13:01 1995 Path: ashpoly!cascade!brgate!saturno!ox!mbrennan From: mbrennan@ox.ac.uk (Min-jun Brennan) Newsgroups: comp.dsp Subject: Re: Discussion: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram Message-ID: <1995Sep27.191301.4176@ox.ac.uk> Date: Wed, 27 Sep 1995 19:13:01 GMT References: <1995Sep27.101001.4744@pipeline.com> <1995Sep27.180001.2993@uni-hamburg.de> Organization: Oxford University Computing Laboratory NNTP-Posting-Host: ox.ac.uk X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1995Sep27.180001.2993@uni-hamburg.de>, smoreno@uni-hamburg.de (Sergei Moreno) writes: > If you decimate to 64 Hz with an 8th-order Chebyshev lowpass, you can run the demodulator in real time on a 386. Have you checked your sound card's ADC clock? Cheap Sound Blaster cards use uncalibrated ceramic resonators that drift with temperature. -- Min-jun Brennan "We don't sign stars. We build them." Commodore Amiga 500 (1MB OCS) / Linux 1.2.13