Return-Path: Received: (qmail 169 invoked from network); 1 Aug 2002 21:08:54 -0000 Received: from murphys.services.quay.plus.net (212.159.14.225) by mailstore with SMTP; 1 Aug 2002 21:08:54 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 14466 invoked from network); 1 Aug 2002 21:08:56 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com (193.82.116.70) by murphys.services.quay.plus.net with SMTP; 1 Aug 2002 21:08:56 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 17aOhI-0005p1-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 01 Aug 2002 23:45:32 +0100 Received: from imo-m06.mx.aol.com ([64.12.136.161]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 17aOhH-0005ow-00 for rsgb_lf_group@blacksheep.org; Thu, 01 Aug 2002 23:45:31 +0100 Received: from DL4YHF@aol.com by imo-m06.mx.aol.com (mail_out_v33.5.) id l.15c.114d17f4 (4262) for ; Thu, 1 Aug 2002 16:53:51 -0400 (EDT) From: DL4YHF@aol.com Message-ID: <15c.114d17f4.2a7af9df@aol.com> Date: Thu, 1 Aug 2002 16:53:51 EDT Subject: LF: Measuring the effective voltage with FFT / SpecLab To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 Content-Type: text/html; charset=windows-1252 X-Mailer: AOL 6.0 for Windows XP DE sub 50 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Content-transfer-encoding: 8bit Hi Andy and group,

>> One way to check would be measure the total power in the signal in a 6kHz (better still 8kHz)
bandwidth and plot this out over a few seconds.   Not unsurprisingly, none
of the PD software available includes this option so I've recorded a few
seconds of .WAV file of this downconverted signal and can have a go at
processing that.
<<

There is such a function in SpecLab's numeric interpreter (now) which calculates the effective voltage in any audio frequency range, based on the results from the FFT calculation. I don't want to bore the group with details, but it may be interesting. With a soundcard running at 44100 samples/second, precise readings can be taken up to a bandwidth of 16 kHz.
The syntax is "veff ( <frequency1> , <frequency2> )". Up to 20 different bands can be observed this way in real time, numeric or as graph, or the results written to a file.

If someone likes to participate, I will upload the new software to my website now (www.qsl.net/dl4yhf/spectra1.html).  The "veff" function is not explained in the manual ! More info and an example configuration file with all required settings available on request.

Regards,
Wolf DL4YHF.