[sdiy] A crazy idea..

[Francois Dion]

Mike Brown wrote:

>most audio interfaces and soundcards have DC blocking caps (soundblaster
>cards, for example)... but you could remove them or shunt them and that
>should work.  I've thought about it many times but never tried it though.
>  
>
Done it when I couldn't afford a scope (in university). It works well. 
Plenty of software now to use your soundcard as a scope including DC:
An oldie:
http://polly.phys.msu.su/~zeld/oscill.html

Brand new, commercial:
http://www.virtins.com/page2.html

Linux:
http://xoscope.sourceforge.net/

More for windows:
http://shmelyoff.nm.ru/

I dont think any of these mention how to get DC sampling... Last one 
specifies ranges as 0 to x where x is half max sampling rate (192KHz 
these days). It also mentions DC voltmeter. Looks pretty impressive, but 
I've not tried it.

>Also, digital audio interfaces generally employ some sort of anti-aliasing
>filtering, so it probably wouldn't work for HF sidebands, etc.
>  
>
On the Yahoo VLF list there's a lot of discussion of using your 
soundcard to tune to VLF stations, pretty neat. I use it for capturing 
spherics and tweeks. There is a software that is used quite a bit to 
build digital tuners. The name escapes me right now, but it is something 
lab. I have it at home.  Ah yes, Spectrum Lab: 
http://www.qsl.net/dl4yhf/spectra1.html

Ciao,
Francois Dion
http://www.cimastudios.com/fdion/