From: Fil Laborde (fil_at_rezox.com)
Date: 2002-01-24 01:23:40
Guys!
I've been asking around and here's the email I got from someone who is part
of an organization dealing with ELF Antennae. Basically he is saying that
there are many analog circuit junkies who use soundcards to display signals
in the ELF range (although they are getting the signals from antennae, ie
submarine transmissions).
So my question is, then, why not pursue an option of using the quality
electronics created here UPTO the bandpass section, and then feed that into
a soundcard and not bother with the complexity of rebuilding the ADC, and
parallel port communications parts. This may give more flexibility to future
possibilities?
Here's the email I got:
----- Email 1 ------
I would suggest you start with a brain wave monitor or eeg circuit. There
are several good designs on the web. Several years ago I buildt a brainwave
monitor from a concept in the ETI magazine. Compared to modern semiconductor
specifications, it as no more the a crude stoneage instrument. But it
worked.
The problem with brainwaves is to separate them, as brain wave patterns are
rather complex and there are several intemidiate states, wich can making
havoc with the indentification of the pure delta/beta/alpha states.
When using a soundcard and suitable software, there are actually no need to
use any kind of "upconverson" of the monitored brain signals. What you need
is very low noise gear, using good noise spec IC's in the preamp and filter
stages.
----- Email 2 -------
Not at all a dumb question ! I know that some brands of soundcards has a
rather "Low Fidelity" respons in the low ranges. But as you know is most of
the amateur ELF monitors using soundcards for display of both Schumann
resonance at 7.8 Hz, as well as general ELF signals in the range below 300
Hz. I have seen several nice recordings and displays of the 2.5 Hz signal
done among other Brian (S7) in the Arizonian desert areas, where he is
involved with Schumann monitoring and detection.
----- END of emails ---
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