Sean
Well I have got my two SG units running and they have recorded several
quakes.  I now have time to start building a version of your VBB.

I have drawn up a version of your circuit which will have a period of 80
seconds (running) and 1 second (zeroing).  I plan to use a 4PDT relay so
that I can switch remotely.  I also plan to put the 'zero motor' control
and calibrate pulse trigger in a remote station along with the period
select switch.

I am currently in the process of wiring up the circuits and have come to
a point where I will have to start cutting metal so that I can check out
my VRDT (the easiest way I can figure out to make a test rig!).  As soon
as I get my boards wired, I will post the drawings.

I do have several questions on your bridge amplifier/Demod circuit for
the VBB.  First, are you using the jumpers near the two 10mF elect and
the 10K pot?  Second, are you using the switch near the two 47mF; if so,
what position?

I do also have another question.  What are the values of the elect
capacitor (C11-C14) on the Seismic Amplifier circuit that you sent me?
I can guess that these would about 25mF Tant?

Thanks in advance

--
Rex Klopfentein, Jr.
rklopfen@.........
http://www.wcnet.org/~rklopfen



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