I am having problems with noise during the night. Oddly it starts about 9:00pm and ends about 11:00 am.

9:00pm WinSDR screenshot  https://home.comcast.net/~bryangoss/noise9pm.jpg

11:00am WinSDR screenshot  https://home.comcast.net/~bryangoss/noise11am.jpg

I think these pictures will explain much more than I can.

I thought it could be because the shop has a concrete floor and the air in the shop heats up to aournd 70F during the day and cools to around 36F at night. I believe the slower cooling of the floor during the night could be causing  convection in the box. I tried to seal the box off and covered it with a blanket but that did not work. Could it be caused by the temperature change in the mineral oil and the vertical dampener?

I ran FFT but to be honest, I'm not sure how to read it.

Thank you for any help you can offer.

Bryan S. Goss



In a message dated 02/04/2005, 1goss@........... writes:

> I got my Lehman Seismometer up and running I think I may have my gain set a 
> bit high, But I think it is ok.

HI Bryan,

       It looks like you have a fairly high gain on the amplifier. I suggest 
that you examine sections of the trace, do a FFT on it and check to see if the 
~six second ocean background is dominant or if there is a lot of other noise. 
Try wedging the mass so that it can't move to check on instrument noise? I 
can't tell much from the drumplot, since I don't know how it was scaled. It 
doesn't show any waveforms or any peak counts. You need to click on X-Scale at the 
top of the display and then select 'counts'. 
       The display shows small deflections during the night, but much larger 
ones during the 'working day'. Do you have a lot of traffic / industrial 
noise?

       What sort of suspensions / bearings are you using? A 12 sec plot 
doesn't give you much 'headroom' over the 6 sec microseisms. 

       Regards,

       Chris Chapman
In a message dated 02/04/2005, 1gos=
s@........... writes:



I got my Lehman Seismometer up=20=
and running I think I may have my gain set a bit high, But I think it is ok.=




HI Bryan,



       It looks like you have a fairly high ga=
in on the amplifier. I suggest that you examine sections of the trace, do a=20=
FFT on it and check to see if the ~six second ocean background is dominant o=
r if there is a lot of other noise. Try wedging the mass so that it can't mo=
ve to check on instrument noise? I can't tell much from the drumplot, since=20=
I don't know how it was scaled. It doesn't show any waveforms or any peak co=
unts. You need to click on X-Scale at the top of the display and then select=
 'counts'. 

       The display shows small deflections dur=
ing the night, but much larger ones during the 'working day'. Do you have a=20=
lot of traffic / industrial noise?



       What sort of suspensions / bearings are=
 you using? A 12 sec plot doesn't give you much 'headroom' over the 6 sec mi=
croseisms. 



       Regards,



       Chris Chapman