Hello Bob;

Have you ever heard of a low noise
GaAs op amp that is designed to work
like a op177G (typical opamp) or ??

Signal to noise ratio should be easily found
in google I think it simply is like
Expectided MDL signal power / Ubiquitous Noise Power
The higher the ratio the better the whatever.
Possibly expressed in db.
For power thats 10Log(Sig/Noi).
The noise would be the reference point.
If you can get a 120db (coopers)
I think youd be in fat city.
The higher the overall s/n ratio
the smaller signals they can see.
Like someone sneezing next door.

:-)
geoff

----- Original Message ----- 
From: "Bob Hancock" 
To: "PSN" 
Sent: Saturday, November 03, 2007 1:16 PM
Subject: Signal To Noise Ratio


When downloading events through IRIS ­ Wilber II, I noticed that they listed
the signal to noise ratio.  Most of the time the number was ­1; however,
there were other numbers listed.  I have some questions and hopefully
someone can answer them.


1.  What is the significance of signal to noise ratio when looking at
earthquakes?

2.  How is signal to noise ratio computed?

3.  What are the ideal numbers to look for and at what point does the data
become unusable?

Thanks

Bob Hancock



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