On Sat, 08 Sep 2001 14:17:08 -0230 Ron Thompsonwrites: > I better clarify this, and BTW my job depends on people breaking > things, someone must keep up the good work :-) > [edited] > Vibration magnitude then is determined by the induced voltage > on the received antenna, and the phase relationship tells us if > the receiver plate moved to one side or the other, but not how far. > I believe that this should work at a frequency where the length > of the coax to the receiving plate should not introduce a > significant phase shift itself, and within the range of cheaper > digital IC's. But, while that might be a clever way to determine direction, I still think that if you do the math, you'll see that to get a measurable phase shift even for a rather significant movement of, say, 1mm, you would need a wavelength of 4 to 10 mm...moving you into the rarified area of the spectrum above 30 Ghz which, even if you could produce and detect it, would make coax just a dream since you would be working with waveguides and cavity tuned elements, and definitely not with cheap IC's. This argument completely ignores the additional problem of the interaction of your detector element with your radiator elements since, in order to receive a signal of any magnitude, it would have to be tuned to some extent, and who knows what phase angles would be present in such a closely coupled environment. If you really want a super-sensitive and novel way of detection, why don't you review the archives for a post I did last year which described a method whereby two oscillators are permeably (and oppositely) tuned by a moving core, and very sensitive frequency changes are, in effect, measured with cheap presettable counters. If fact, I think I even biased the coils with dc feedback to make it a force-balance instrument at the same time. I have not had the time to build it, but I know it will work. And so there is more grist for our ever grinding mill... Tom __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>