[time-nuts] Oscilloscope-based measurements of frequency stability

Christoph Kopetzky ck at cksd.de
Wed Oct 10 09:50:51 EDT 2018

Hello Dana,

thank you for your detailied description. I will try this out in the 
next days.
Scopes became a right normal permanent instrument in the electronics lab 
of time-nuts
like a multimeter for the electrician.
Before I connect a counter onto a signalsource which I want to 
characterize I am first looking with the scope on it.
A few month ago I built an dual card for a quarz ofen oscillator from Eb...
After measuring the output frequency on both channels I was wondering 
why this one  gave absolute nonsense instead of the expected 10 MHz count.
After some experiments I hooked on the scope and looked on the signaltrace.
Instead of a pure sinusoidal signal which I assumed the scope showed a 
distorted multisinusoidal signal which had no definitive wavelength but 
a overlapped
form with several peaks like a modulated sinusoidal carrier wave mixed 
with with another sinusoidal signal with a frequency relation of 10 : 1.
After rerouting some circuit tracks and optimizing the shielding the 
effect was gone.
So this was the reason why my scope became an every time instrument in 
my lab.


mit freundlichen Gruessen - with best Regards

Christoph Kopetzky

Am 07.10.2018 um 23:03 schrieb Dana Whitlow:
> Hello,
> Here is the promised discussion (from about a week ago) of my scheme for
> using a DSO to capture the information needed to produce detailed plots of
> phase and frequency modulations of a noisy source under test.
> Alas, the method is apparently inadequate for characterizing a source as
> quiet as I feel I need for some future experiments, but I felt that the
> method
> itself (if implemented with better equipment) could be of interest as an
> alternative to TIC-based methods.  The text file also includes some
> discussion
> of a different method that I feel will probably be better suited to my
> future
> needs.

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