Bonsoir Magnus (Are you in Sweeden ?) Being able to measure high stability and low phase noise is definitely a need for me as I'm trying to design low noise synthesizers and I'm already reaching the limits of my current tools for phase noise and I can't afford an E5052 for my own. At work I've one but I will probably not stay after august. And anyway I need such tools in my lab at home... As low-noise and stable synthetizers depends on the standard used, I need as well to measure them as well...
Let's start with this simple experiments and once I will understand the ins and outs I will try to improve. I know techniques of cross-correlations and you've already talked about DMTD that for sure I will have to come to... Good night Stephane -----Message d'origine----- De : Magnus Danielson [mailto:[email protected]] Envoyé : dimanche 18 janvier 2015 22:46 À : Stéphane Rey; 'Discussion of precise time and frequency measurement' Cc : [email protected] Objet : Re: [time-nuts] question Alan deviation measured with Timelab and counters Bonsoir Stéphane, On 01/18/2015 10:34 PM, Stéphane Rey wrote: > Thanks a lot Bob and Magnus for your very helpful comments. > > The HP5370a was indeed in TI mode. By the way what is the difference with > +/-TI, the button just aside... > > But I guess I understand where I've missed something : I've tried to put the > Rb on channel A and the DUT on channel B but result was always the same but I > do understand now that there is indeed a switch to change from COMmon to > SEParate and it was always on COM meaning I believe that channel B wasn't > used. This explains a lot of things I did not understand. I'm sorry for these > so basic issues that might have been solved if I had read carefully the > HP5370a manual first. Good. This confirmation makes sense to be and Bob, now we can relax as the mystery is solved. > So possible conclusions until now are that I have actually measured the ADEV > floor of the system rather than my DUT... which is already nice. The second > conclusion from these oscillations seen with the GPSDO under test is that > there is very likely in this GPSDO design a systemic noise added to the 10 > MHz output (power supply, PCB coupling, ... I'll make further investigations > on it later on). It's a great opportunity to learn the tools, and once you have the tools, you can see if you can't improve things. > I will experiment all the suggestions you made and will come back. For > information the 1PPS from the HP58503b has a positive pulse width that is > only few us length. This only makes it hard to view on a scope, but long enough to reliably trigger your counter and scope. > Now, when considering that the method is to compare the DUT to an other > source, I assume then that the other source shall be at least 1 order of > magnitude better than the DUT. Otherwise this will be impossible to > distinguish who is the instability contributor between the source and DUT, > right ? For a simple setup, yes. But then we are the time-nuts, we have ways of handling these things. :) Let's get you started with the basic measurement, it will be a good start. > Then the second question is what kind of very stable source can be used to > measure DUT which could be Rb or GPSDO which are already in the range of > 10E-10 to 10E-12 < 100s ? Time-nuts tend to spend their time and money getting even more stable clocks and tools. If you have the right tool, you can measure near and *under* the noise-level of your reference, but not without running into issues. One such trick is called cross-correlation, while another is to use three-corner hat techniques. Cheers, Magnus --- L'absence de virus dans ce courrier électronique a été vérifiée par le logiciel antivirus Avast. http://www.avast.com _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
