Hi Chris

Thanks for the Lennartz information.

I seem to get AS1 comparable performance on a 4.5 Hz
geophone system without ANY frequency compensation,
all the way down to surface wave frequencies around 0.04 Hz.

I am concentrating on getting the lowest possible system
noise by using one of the newest ultralow noise auto-zero opamps
that has NO 1/F noise.  I run it at 100,000x gain.  These opamps
are less than $2, but they are very small surface mount parts that
are tricky to hand solder, at least for me
http://www.analog.com/en/precision-op-amps/low-voltage-noise-amplifiers/ada4528-1/products/product.html

My system is sitting on a carpeted basement floor of a busy office building
near Washington, DC and my online helicorder display shows todays
Costa Rica 5.8 quake at around 11 UTC.
http://www.infiltec.com/seismo/qm45.htm
I use the typical AS1 bandpass filtering of 10 to 25 seconds to
get the most sensitivity to teleseismic events.

My helicorder today looks a lot like the Columbia University broadband
display
showing the Costa Rica quake.
http://www.ldeo.columbia.edu/cgi-bin/LCSN/WebSeis/24hr_heli.pl

I am about 30 degrees from Costa Rica and Columbia University is near NYC
and about 32.5 degrees acording to usgs.
http://neic.usgs.gov/neis/bulletin/neic_b0007ztb_t.html

The P wave does not show up very well on my filtered helicorder, or on the
Columbia
U broadband.  But if I set my helicorder to unfiltered and get the whole
..01 to 1.0 Hz band
it shows up well, just like the Columbia University short period display.

I am amazed a how much performance you can get without any compensation
for the 4.5 Hz geophone steep 1/f^2 loss.

I do not think any of the IRIS AS1 display shows the Costa Rica quake today
http://www.iris.edu/hq/ssn/schools/realtime

Cheers,

Dave
Hi Chris

Thanks for the Lennartz information.
=

I seem to get AS1 comparable performance on a 4.5 Hz
geophone system without ANY=A0frequency compensation,
all the =
way down to surface wave frequencies around 0.04 Hz.


I am concentrating on getting the lowest possible syste=
m
noise by using one of the newest ultralow noise auto-zero opamp=
s
that has NO 1/F noise. =A0I run it at 100,000x gain. =A0These o=
pamps

are less than $2, but they are very small surface mount parts that
are tricky to hand solder, at least for me
http://www.analog.com/en/precision-op-amps/low-vo=
ltage-noise-amplifiers/ada4528-1/products/product.html

My system is sitting on a carpeted basement floor=
 of a busy office building
near Washington, DC and my online heli=
corder display shows todays
Costa Rica 5.8 quake at around 11 UTC=
..

http://www.infilte=
c.com/seismo/qm45.htm
I use the typical AS1 bandpass filtering of 10 to 25 seconds to<=
/div>
get the most sensitivity to teleseismic events.

My helicorder today looks a lot like the Columbia University broadb=
and display

showing the Costa Rica quake.
http://www.ldeo.columbia.edu/c=
gi-bin/LCSN/WebSeis/24hr_heli.pl=A0

I am about=
 30 degrees from Costa Rica and Columbia University is near NYC

and about 32.5 degrees acording to usgs.
http://neic.usgs.gov/neis/=
bulletin/neic_b0007ztb_t.html=A0

The P wave do=
es not show up very well on my filtered helicorder, or on the Columbia

U broadband. =A0But if I set my helicorder to unfiltered and get the w=
hole .01 to 1.0 Hz band
it shows up well, just like the Columbia =
University short period display.

I am amazed a how=
 much performance you can get without any compensation

for the 4.5 Hz geophone steep 1/f^2 loss.

I d=
o not think any of the IRIS AS1 display shows the Costa Rica quake today
http://www.=
iris.edu/hq/ssn/schools/realtime=A0


Cheers,

Dave