[time-nuts] I can't get a nice waveform from my rubidium !

Volker Esper ailer2 at t-online.de
Thu Apr 17 16:19:34 UTC 2014

Hi Claude,

Am 17.04.2014 07:32, schrieb Claude Fender:
>  connect an output directly to the oscilloscope, the shape is nearly 
> "squared" and when I use a probe, the shape is nearly "sine" !
> When I send a 10 MHz signal from a generator, the waveform is a clean sine with or whithout the probe.
I assume you use the same probe for the generator and the rubi.
Was the probe calibrated for square wave? That's important - if you
haven't calibrated it yet, you should do that at first.
Are you using the 1:1 position? What, if you use a 1:10 probe/position?
Is it the original Rigol probe?
What is the output impedance of your generator, 50 ohms?
What is the output impedance of your Rubidium? If you don't know,
attache a trim-pot as load, in parallel to the scope (without probe).
Adjust the pot until the output voltage has dropped to half of the
unloaded voltage. Measure the value of your pot - that's the output
resistance of your Rubidium.

What I imagine: the probe isn't calibrated or has a problem, the
Rubidium output is square wave, but the probe doesn't respond correctly
(to low the upper cut-off frequency). The generator will always look ok
(with or without a defective probe), since it outputs a sine wave anyway.



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