[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 
totally
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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