In a message dated 08/01/2007, royb1@........... writes:

There us  currently a digital Rockland on ebay but it looks expensive and 
I don't  know the specs.  The analog version comes up  occasionaly.



Hi Bob,
 
    I haven't read the data manual for a Rockland  Digital Filter, but the 
problem with digital filters for seismic use has  previously been their low 
dynamic range. They are simply too noisy and may  give less than 80 dB, where over 
120 dB would be desirable. 
 
    Regards,
 
    Chris Chapman






In a message dated 08/01/2007, royb1@........... writes:
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  currently a digital Rockland on ebay but it looks expensive and 
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  know the specs.  The analog version comes up=20
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Hi Bob,
 
    I haven't read the data manual for a Rockl=
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Digital Filter, but the problem with digital filters for seismic use has=20
previously been their low dynamic range. They are simply too noisy and=20=
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give less than 80 dB, where over 120 dB would be desirable. 
 
    Regards,
 
    Chris Chapman