[sdiy] Soundcard spectrum analyzer?

[JH.]

>Are you sure you want a BPF on the input ? Having the noise and
>distortion products lumped together with the signal is not ideal
>but isn't that more useful than not seeing them at all ?
>
>If the filter under test is resonant, it will ring at Fc even if
>the input frequency is far from Fc. A BPF will make the FUT appear
>more selective than it really is.

Yeah right - a sweeping sine tone and an envelope follower is enough for my 
purpose.
Or white noise and a sweeping BPF filter ...
or a sweeping SSB modulator and a fixed BPF filter ...

What I intended to say is that I distrust a raw FFT unless it has an 
enormour amount of bins, and don't know enough about the chirp method I 
found advertised in one of the shareware programs ...

JH.