PSN-L Email List Message

Subject: Re: plum bob seismometer
From: Karl Cunningham karlc@..........
Date: Thu, 16 Nov 2006 13:20:35 -0800

On 11/15/2006 11:25 AM, Allan Egleston wrote:
> Has any one on the list experimented with a blumbob as a seismo and
> have had any sucess wit hit?
> Thanks in advance , Allan Egleston kf6uxj


I wont duplicate Chris Chapman's comments, but if you want something 
simple to construct you might consider the inverted pendulum (think 
rocking chair). This can be as simple as a car radio antenna with a 
heavy ball fastened to the top. These can be metastable and have 
linearity issues, but if all you want is a long period it is possible to 
get that for small excursions.

Karl Cunningham

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