LF: Measuring the effective voltage with FFT / SpecLab

To:	[email protected]
Subject:	LF: Measuring the effective voltage with FFT / SpecLab
From:	[email protected]
Date:	Thu, 1 Aug 2002 16:53:51 EDT
Reply-to:	[email protected]
Sender:	<[email protected]>

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.

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