> > Javier Herrero wrote: > > Hello, > > > > I will need to measure the phase noise of a 35MHz oscillator in the > > range of 1 to 100Hz (well... and also at a higher range but this is no > > problem), and I would like to know about the different alternatives. I > > would like not to have to mess too much with mixers and soundcard > > sampling, if possible :)
You probably need to find someone with an HP 3048A or similar outfit. A TSC 5125A will also do the job. The requirement to go below 100 Hz takes a lot of the 'easy' solutions like the 11729C out of contention. > > I think that the HP 5372A with opt 040 is able to do that, is this > > right and worthy? If so, opt 040 is a pure software option or requires > > also additional hardware? Would be possible also with a 5370A and > > software processing of the raw data? Any other alternatives? > > > > Thanks! Regards, > > > > Javier > > > The 5372A or 5370A will only suffice if the phase noise is sufficiently > high. > They are likely to be too noisy by several orders of magnitude for a > good crystal oscillator. That was my first thought as well, but the 5370 might be OK for measuring TCXOs and the like. An HP paper from the mid-1970s suggests that it's possible to reach ~-150 dBc/Hz at 1 Hz with contemporary hardware (5345A-based, 2-ns resolution): http://www.hparchive.com/seminar_notes/a-114.pdf They mix down to a low IF before measurement, which they appear to vary in order to get a lower floor at close-in offsets. If nothing else, it should be possible to back the PN spectrum out of an ADEV graph plotted with data from a counter, taking the noise slope into consideration. It would take a lot of hacking (not to mention the effort needed to get hundreds of measurements per second out of the counter, which I also haven't looked into.) There's a more user-friendly app note here: http://www.ko4bb.com/Manuals/HP_Agilent/1%29_HP_App_Notes/HP_AN225_Measuring _Phase_Noise_with_HP_5390A.pdf Could be a reasonable way to measure PN at offsets below 10 or 100 Hz, at least until the higher-order noise slopes invalidate some of the assumptions baked into the software. It wouldn't scale very well to broadband offsets in any event. -- john, KE5FX _______________________________________________ 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.
