Hi Geoff,
 
  There is a better way to extend the response of a 1 Hz geophone, or  any 
open loop sensor. Try the period extending filter in WQFilter.exe. Use  normal 
damping. The filter can extend the period by a factor of 8 or more on  major 
events. This is a digital inverse filter, whose gain is shaped to preserve  
normal gain at high frequencies and to supply the gain needed at frequencies  
below the natural frequency of the sensor. The utility can be downloaded  from
 
   _http://www.jclahr.com/science/psn/mcclure/sac/index.html_ 
(http://www.jclahr.com/science/psn/mcclure/sac/index.html) 
 
  This program includes high-pass and low-pass Butterworth filters  which 
perform better than those supposedly IIR BW filters in WinQuake. I have  learned 
never to use WinQuake's filters. I use the lowest order, order 2, both  
directions for high-pass filtering. Extended period filtering works best if  you 
select the option "LONG PERIOD plus HPF". Additional high-pass filtering is  
usually unnecessary if you use that option. Even long period period Lehman  
sensors can benefit from proper use of WQFilter, as it can compensate for over-  or 
under-damping. It can make the filtered long period response either longer or  
shorter than the actual sensor period.
 
  On an unrelated note, those of you who use HP calculators with  Reverse 
Polish Notation will like the following freeware calculator for your PC  desktop:
 

 _http://www.tordivel.no/xcalc/_ (http://www.tordivel.no/xcalc/) 
 
Bob
 
In a message dated 12/10/2007, gmvoeth@.... writes:
 
I have a  vertical setup with a sensor that seems to have a  sensitivity of 
1.5 to 2  volts per inches per second and I can see a  magnitude 4 about 6 
degrees away.  or so it seems. I am using heavy  damping to allow me to use a 
single 
bandpass  filter to equalize the  freq response of a one hertz geophone 
somewhere  between 4 seconds and  2 Hz.



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Hi Geoff,
 
  There is a better way to extend the response of a 1 Hz geophone,=
 or=20
any open loop sensor. Try the period extending filter in WQFilter.exe. Use=20
normal damping. The filter can extend the period by a factor of 8 or more on=
=20
major events. This is a digital inverse filter, whose gain is shaped to pres=
erve=20
normal gain at high frequencies and to supply the gain needed at frequencies=
=20
below the natural frequency of the sensor. The utility can be downloaded=20
from
 
   http://www=
..jclahr.com/science/psn/mcclure/sac/index.html
 
  This program includes high-pass and low-pass Butterworth filters=
=20
which perform better than those supposedly IIR BW filters in WinQuake. I hav=
e=20
learned never to use WinQuake's filters. I use the lowest order, order 2, bo=
th=20
directions for high-pass filtering. Extended period filtering works bes=
t if=20
you select the option "LONG PERIOD plus HPF". Additional high-pass filtering=
 is=20
usually unnecessary if you use that option. Even long period period Lehman=20
sensors can benefit from proper use of WQFilter, as it can compensate for ov=
er-=20
or under-damping. It can make the filtered long period response either longe=
r or=20
shorter than the actual sensor period.
 
  On an unrelated note, those of you who use HP calculators with=20
Reverse Polish Notation will like the following freeware calculator for your=
 PC=20
desktop:
 

 http://www.tordivel.no/xcalc/
 
Bob
 
In a message dated 12/10/2007, gmvoeth@.... writes:
 
I have a  vertical setup with a sensor that seems to have a=20
sensitivity of 
1.5 to 2  volts per inches per second and I can see=20=
a=20
magnitude 4 about 6 
degrees away.  or so it seems. I am using heavy=
=20
damping to allow me to use a single 
bandpass  filter to equalize th=
e=20
freq response of a one hertz geophone 
somewhere  between 4 seconds=20=
and=20
2 Hz.


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=