PSN-L Email List Message

Subject: Fw: Fw: it happened again
From: "Tom Schmitt" tschmitt@..............
Date: Wed, 26 Jul 2000 21:42:21 -0400


This is the responce Bob Duckworth gave when I sent him a descriptions of
the problem.
Bob used to run the Ga Tech seismic net work and also did some shipboard
exploration seismic stuff.

He did not have benefit of all the discussions.  It is interesting that he
has much the same train of thought as Sean-Thomas, ie there is a bad joint
doing the rectification.   Sean-Thomas focused on the ground and Bob focused
on a process to find the rectification but both had the same goal.

SeanThomas, off list I want to ask you why a Farday cage won't work on am

Tom Schmitt


> 2) If you have a DC offset then then you are rectifying somewhere in
>    your circuit. Culprit will be exposed to the RF and nonlinear.
>    i.e. Joint in wiring between dissimilar materials, oxidized joint,
>    amplifier driven into nonlinear region by RF
> Solutions. Make sure all joints, connections are tight with no
> oxidation, make sure you have no common mode amplification, minimize RF
> in all circuits.
> Break you circuit down into sections. Start with the recorder.
> Short the input. Does offset change. Work your way back to the sensor.
> Somewhere along here you are rectifying.
> -bob
> rb


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Larry Cochrane <cochrane@..............>