I am working on an STM-8 - all the mechanical is done
and I'm in the process of preparing an order for the
electronics.  In the meantime, I connected the
Feedback transducer (the speaker was the only
"electronics" I had for it so far) to my recorder. 
I'm getting real nice low frequency signals from it. 
I can see from 30 seconds to 500 Hz.  The roll off: 
30 seconds is at -30db relative, 1 Hz is at about
-35db relative, then, it really rolls off after 4 Hz. 
I can see a small peak at 2.3 seconds - the period of
the seismometer.

I'm using a modified sound card to display/record the
signal.  I built a low-frequency oscillator to check
the response of the sound card - works great.

Anyway, I thought it was interesting to get such a
good signal from just the feedback transducer and I
thought you all might like to know.

Greg

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