Hi You can make a pretty good "front end" (mixer / amp / lock) for under $100. That will let you measure phase noise with an audio spectrum analyzer.
Bob On Aug 20, 2010, at 10:40 AM, Adrian <rfn...@arcor.de> wrote: > Mark, > > you have the following options: > > - HP (Agilent) E5052A/B or R&S FSUP Signal Source Analyzer (works for a > single DUT, though limited to 1 Hz offset, normally useful for 10 Hz up to 40 > MHz). > - Compare two identical DUT's with a HP 3048A or similar PN test system and > subtract 3 dB, assuming that the PN characteristic of both DUT's is identical. > - Compare 3 similar DUT's with a HP 3048A and calculate the individual PN > using the three cornerd hat method. > - set up a cross correlation PN measurement system similar to the E5052A and > have fun. You will however need two - as good as possible, but preferaby not > more than 10 dB worse than what you want to measure - VCXO's like HP > 10811A's... > - you may build your own HP 3048A alike system, but be prepared to invest > serious money and time, and much more time than you thought in the > beginning... (if that is what you're after, you'll have the most fun you can). > - find someone who has one of the above and talk him into measuring yours. > - search the web for published PN data of the model you have and take these > as a reference (give or take a few dB). > Btw. do not assume that the phase noise of a disciplined VCXO is the same as > the VCXO alone. > Also keep the power supply contribution into account that can be surprisingly > high. > And, the PN of most frequency standards is significantly lower than what you > can measure with any spectrum analyzer with PN measurement software (except > for the R&S FSUP of course). > > Adrian > > > Grant Hodgson schrieb: >> Mark >> >> You've come to the right place - well, that is if you want to devote a >> significant amount of your life in the pursuit of ever-more accurate time >> and frequency measurements.... >> >> If you've only got one source then you need to use the frequency >> discriminator method (aka delay line method) of phase noise measurement. >> Basically you take the output of the source, split it in two, delay one of >> the signals, re-combine the two and then measure the resultant signal on a >> base-band spectrum analyser. >> >> There are loads of references to this on the web, which describe the method >> in more detail, including :- >> >> The Art of phase noise measurement - Dieter Scherer >> >> and >> >> HP Application Note AN270-2 >> >> both available from John Miles web site >> >> www.thegleam.com/ke5fx/gpib/pn.htm >> >> The references at the end of these articles, especially the HP ones, are >> particularly useful. The operating manual for the HP 11729B or 11729C >> Carrier Noise Test Set is also highly recommended. >> >> Yes, there's some maths, you need to understand the relationship between >> phase and frequency measurements, but you don't necessarily need ALL the >> theory that most of the papers give - don't give up just because of a few >> differential equations :) >> >> The limitation of the frequency discriminator method is that the noise floor >> of the measurement system is often worse than the DUT, especially if your >> DUT is very good, and it's even worse if you're trying to measure close-in >> noise. The Sherer article gives a good graph illustrating this. If you're >> trying to measure the phase noise of the oscillator inside a Tbolt then I >> don't think that a frequency discriminator will be sensitive enough, >> although I might be wrong. >> >> Despite what you said, you might want to consider buying an HP 10811 >> oscillator or similar which you could use in a phase detector measurement >> system which is likely to give superior results. >> >> Hope that helps >> >> regards >> >> Grant >> >> Mark wrote :- >> >> My new GPSDO leaves me with the question of "how do I measure the phase >> noise of what is by far the best oscillator I own... without buying a better >> one to compare it to". That question is what brought me to time-nuts. I'm >> starting to read some papers on oscillator characterization that are >> collected together in a technical note from NIST that a co-worker pointed me >> towards, but some of them are giving me a math-induced headache. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
