From: "Randy Pratt" rpratt@.............

Date: Thu, 24 Dec 2009 11:31:51 -0600

Dr Peters, After suggesting the sideband method I began researching how. It = appears doing this digitally is a bit more complex than anticipated. I = did find that people in other fields such as ultrasound are using a = Hilbert transform to produce the information. I don't know what = obstacles this would involve as to sample rate limits or translation to = the extremely low frequencies from the MHz ranges they are using. It = looks like an interesting topic for winter night study. AmaSeis can = export the FFT of a segment of data as a starting point or an FFT = followed by the Hilbert transform could be coded directly once all the = limitations are known. I wonder if an analog demodulator could be added to the seismograph = using the microseism frequency of a second instrument as a continuous = tuning device for the carrier wave. Randy=20Dr Peters,After suggesting the sideband method I = began=20 researching how. It appears doing this digitally is a bit more = complex=20 than anticipated. I did find that people in other fields such as=20 ultrasound are using a Hilbert transform to produce the = information. I=20 don't know what obstacles this would involve as to sample rate limits or = translation to the extremely low frequencies from the MHz ranges they = are=20 using. It looks like an interesting topic for winter night=20 study. AmaSeis can export the FFT of a segment of data as a = starting=20 point or an FFT followed by the Hilbert transform could be coded = directly=20 once all the limitations are known.I wonder if an analog demodulator could = be added to=20 the seismograph using the microseism frequency of a second = instrument as a=20 continuous tuning device for the carrier wave.Randy