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EEVBLOG #21 Scope Phenomenon

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sanman:
I didn't see any recent posts regarding 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?

EEVblog:

--- Quote from: sanman on June 12, 2010, 07:49:11 pm ---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?

--- End quote ---

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.

Strube09:
I tried this in my office a few weeks back and sure enough it worked.... but as for the spring in the chair BS I can say it is untrue.... My chair is fixed with nothing moving.

At the end he even used a terminating resistor and still had it resonate but it was at a slightly different frequency, as I would expect. Without the complete probe your LC tank has completely changed and I would expect a higher resonant frequency.

Just my 2 Cents.

kc1980:
This offers a pretty good explanation:

http://www.emcesd.com/pdf/eos93.pdf

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