All I know is signal to noise ratio is one of the
most important characteristics of any
sensor. You want the sensor noise and electronic
noise to reside
lower than the ground noise
in the most quiet of areas.
I think a supercooled sensor is the only way
to do this unless the natural noises
are great. Pioneer had this thing called
a supertuner which would let me
see radio waves bouncing off ion trails
left by meteors. Built a 3 element
yagi-uda adjustable so it could be tuned
anywhere in the FM band and between that antenna
and the supertuner I had great fun listening into
FM stations over 1000 miles away when certain
meteors streaked below about 45deg elevation
normal to my location.
I think the supertuner used the then newly
built gallium arsinide front ends that were the
best signal to noise ratio of the time 1990 ??
That is the kind of hardware we need too.

I think there exists the possibility of somehow
demodulating the noise to witness a general
increase in its overall amplitude to
receive signals lower then the noise yet
since it sums with the noise will present
itself as an increase in the noise but you
can not see the actual signal doing this.
They do this in signal analysis by integrating
signals over long periods of time like 24 hours
just to look for one kind of signal or other.

It seems you can see signals up to -40Db below the background???
To me that is a level 0.01 the actual noise itself.

???

Wish i knew more but when the USA lables one mentally ill
the relm of meaningful technical research and development can
only be learned through the process of educational/informational
osmosis.

:-)
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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