Sean Thomas
    I responded because my designs frequently change and I thought maybe you
had improvements.  I do have your posting, and in fact I bought the magnet as
well. Small is where I'm going. I currently have a 10"  leaf spring vertical.
It however is using a 6" speaker coil and homemade lvdt. It still records
teleseismic events well but has a poor response to events closer than ~200k.
My full size smt8 style sensor responds better to local events as I
anticipated. I have a homemade calibrated vrdt which I made. Combined with a
homemade feedback coil which you have described, I am hopeing to put
everything in a sealed insulated ammo box for field use. Thanks again for all
your help over time.
Regards
Barry



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