In a message dated 31/03/2006, system98765@............. writes:

Hi Chris  (& everyone else),
Where can one get more information about the  'Roberts Amplifier'? 
Kareem



Hi Kareem,
 
    Go to _http://psn.quake.net/bibliography.html_ 
(http://psn.quake.net/bibliography.html)  
 
    Roberts, PM "A Versatile Equilization Circuit for  Increasing Seismometer 
Velocity Response Below the Natural Frequency." (for  4.5Hz geophones) BSSA,  
vol 79, pp 1607-1617 Oct. 1989
 
    Your local library should be able to get you a  photocopy.
 
    I made some simple circuit changes which reduced  the very low frequency 
noise, if anyone is interested. The modified circuit  seems to work fine. 
Lennartz use geophone compensators of this general type on  their professional 
range. You get about a factor of 10 reduction in the minimum  frequency - e.g. a 
4.5Hz geophone will reproduce ~flat down to 0.45Hz. This  enables you to pick 
up teleseismic quakes as well as local and regional  ones.
 
    Regards,
 
    Chris Chapman
 






In a message dated 31/03/2006, system98765@............. writes:
<=
FONT=20
  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>Hi Chris=20
  (& everyone else),
Where can one get more information about the=20
  'Roberts Amplifier'? 
Kareem


Hi Kareem,
 
    Go to http://psn.quake.net/bibliog=
raphy.html 
 
    Roberts, PM "A Versatile Equilization Circuit f=
or=20
Increasing Seismometer Velocity Response Below the Natural Frequency." (for=20
4.5Hz geophones) BSSA,  vol 79, pp 1607-1617 Oct. 1989
 
    Your local library should be able to get you a=20
photocopy.
 
    I made some simple circuit changes which reduce=
d=20
the very low frequency noise, if anyone is interested. The modified circuit=20
seems to work fine. Lennartz use geophone compensators of this general type=20=
on=20
their professional range. You get about a factor of 10 reduction in the mini=
mum=20
frequency - e.g. a 4.5Hz geophone will reproduce ~flat down to 0.45Hz. This=20
enables you to pick up teleseismic quakes as well as local and regional=20
ones.
 
    Regards,
 
    Chris Chapman