I did see any recent posts with regarding to the spurious signal issue.
We see this a lot in model helicopters with metal rubbing against metal. Could this be caused by the metal in the chair when Dave stands up?
It's caused by the static electricity between my pants and the fabric of the chain when I stand up. I can get the same effect many ways, I just found the chair a consistent method.
People think it's all sorts sorts of things like the piston in the chain resonating and all sorts of weird things, it's non of that, it's simple static generation.
The real mystery is how it actually manifests itself in the front end of many different scopes so consistently.
Dave.