Recording DC-20Hz via soundcard

FM in CEP -- I dont think so -- you have a transformation from tone to voltage that you cannot "program" into CEP, as its based on the values of the components used to adjust the VCO

Being a programmer, I would write code to sample the sound card directly and implement a zero crossing detector.. since its a pure tone, that will give me the frequency, and the math given in that article will give you the inverse transform to convert that to a voltage. There is plenty of sample source code out there for accessing the mic input as raw 8 or 16 bit data using DirectSound, and with sample rates up to 44khz, you could run the VCO from 100hz to 20khz range without dropping data needed to detect the zero crossings.. then the only question is, how long a period of time do you count crossings before converting -- the longer you count, the more accurate the conversion.

If you have ever worked with C# -- I could scare up the capture routines from one of my RF to Internet bridge applications .. get you going in the right direction :)

On a sunny day (25 Feb 2007 22:11:37 -0800) it happened snipped-for-privacy@hotmail.com wrote in :

Wrong way around. First use a low pas gradual filter, then you are left with an amplitude modulated RF signal (amplitude depends on frequency).

It is called 'flank' detection.

If you 'rectify' that you have the original sort of. But it is not very linear.

Better to do it in software yourself.

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