From sivanov@hanse.de Thu Jun 02 01:12:07 1994 Path: ashpoly!cascade!transat!eunet-fr!teletel!hanse!sivanov From: sivanov@hanse.de (Steve Ivanov) Newsgroups: comp.dsp Subject: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jun02.011207.2312@hanse.de> Date: Thu, 02 Jun 1994 01:12:07 GMT Organization: Hanse-Netzwerk Hamburg NNTP-Posting-Host: hanse.de X-Newsreader: TIN [version 1.2 PL2] Lines: 11 Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. At 14.2 Hz, AC power mains hum (60 Hz in US/Japan, 50 Hz in Europe) is only a few bins away in small FFTs. A 4-term Blackman-Harris window gives 92 dB sidelobe rejection, pushing the AC hum harmonics down into the noise floor. Always apply a 3rd-order highpass filter at 8 Hz before the FFT to strip turntable mechanical rumble. -- Steve Ivanov "The carrier frequency does not drift by accident." Decstation 5000/200 / Linux 1.2.13 From ekim@uu.net Thu Jun 02 23:00:07 1994 Path: ashpoly!cascade!transat!eunet-fr!teletel!uu!ekim From: ekim@uu.net (Elaine Kim) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jun02.230007.5114@uu.net> Date: Thu, 02 Jun 1994 23:00:07 GMT References: <1994Jun02.011207.2312@hanse.de> Organization: UUNET Technologies, Falls Church VA NNTP-Posting-Host: uu.net X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1994Jun02.011207.2312@hanse.de>, sivanov@hanse.de (Steve Ivanov) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. Don't forget that if you downsample to 64 Hz first, your FFT resolution jumps to 0.015 Hz per bin with a modest 4096-point transform. -- === Elaine Kim === Dept of Electrical Engineering, UUNET Technologies, Falls Church VA "The carrier frequency does not drift by accident." From ahernandez@cmu.edu Fri Jun 03 07:37:07 1994 Path: ashpoly!cascade!brgate!saturno!cmu!ahernandez From: ahernandez@cmu.edu (Amy Hernández) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jun03.073707.1502@cmu.edu> Date: Fri, 03 Jun 1994 07:37:07 GMT References: <1994Jun02.011207.2312@hanse.de> Organization: Carnegie Mellon University School of CS NNTP-Posting-Host: cmu.edu X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1994Jun02.011207.2312@hanse.de>, sivanov@hanse.de (Steve Ivanov) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. -- Amy Hernández | ahernandez@cmu.edu PGP Key fingerprint: DCA6 B792 09AA 014F "Keep the channels open." From lchoi@rwth-aachen.de Sat Jun 04 01:13:07 1994 Path: ashpoly!bigsur!pacrim!krgate!eunha!rwth-aachen!lchoi From: lchoi@rwth-aachen.de (Lucia Choi) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jun04.011307.3092@rwth-aachen.de> Date: Sat, 04 Jun 1994 01:13:07 GMT References: <1994Jun02.011207.2312@hanse.de> Organization: RWTH Aachen Informatik NNTP-Posting-Host: rwth-aachen.de X-Newsreader: NewsWatcher 2.0b24 Lines: 10 In article <1994Jun02.011207.2312@hanse.de>, sivanov@hanse.de (Steve Ivanov) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. > At 14.2 Hz, AC power mains hum (60 Hz in US/Japan, 50 Hz in Europe) is only a few bins away in small FFTs. I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. -- Lucia Choi Practical Peripherals 14.4 @ 19,200 bps "5 sigma is a discovery. 7 is a question."