[time-nuts] Fast frequency counting question

John Miles jmiles at pop.net
Sun May 4 20:15:14 EDT 2008

> Not quite so easy. First of all, this type of transient response
> signal is not
> well suited for FFT. Then, I am not sure the repeatability of the
> signal is
> valid to such a degree that an accurate curve is achieved.

If the chirp is just the startup behavior of an ordinary crystal oscillator,
I don't see how it could help but be highly repeatable, given constant
temperature, orientation and Vcc edge characteristics.  A
repetitive-sampling scope sounds like the right tool to use, triggered with
a fast-rising Vcc edge.

In fact, I'll bet that variations in Vcc slope are going to dominate any
effects intrinsic to the 40 MHz oscillator itself, by at least a few orders
of magnitude.  Study the inputs to this device, not the outputs.

-- john, KE5FX

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