Hi.

Im using a L4 1Hz geophone and for almost a month im struggling with high
noise from 10s up to ..., but from <10s it looks good. The noise comes and
goes, this image is self explaining:

http://dl.dropbox.com/u/15802004/noise.png

Changed cables, re centered the geophone, but didint help..the geophone is
connected directly to a ADC without damping, external amplification or
filtering, i only use digital filtering from the ADC. Before this issue
start, i had a pretty clean spectrum >10s for almost 6 months, which
allowed me to received LQ and LR from some strong events.

This sac contains 15minutes with high noise >10s, notice that at 3:37 it
recorded a Ml2.1 at 70km.
http://dl.dropbox.com/u/15802004/noise.sac

What could be the problem?

I appreciate any help.

Best Regards,
Tiago.
Hi.

Im using a L4 1Hz geophone and for almost a month im struggling =
with high noise from 10s up to ..., but from <10s it looks good. The noi=
se comes and goes, this image is self explaining:

http://dl.dropbox.com/u/15802004/noise=
..png


Changed cables, re centered the geophone, but didint help..the geophone=
 is connected directly to a ADC without damping, external amplification or =
filtering, i only use digital filtering from the ADC. Before this issue sta=
rt, i had a pretty clean spectrum >10s for almost 6 months, which allowe=
d me to received LQ and LR from some strong events.


This sac contains 15minutes with high noise >10s, notice that at 3:3=
7 it recorded a Ml2.1 at 70km.
http://dl.dropbox.com/u/15802004/noise.sac

What co=
uld be the problem? 


I appreciate any help.

Best Regards,
Tiago.