The mixer output is only sensitive to phase differences for small deviations about 90 degrees phase difference between the 2 sources. With unlocked sources AM noise also affects mixer output. In order to measure phase noise without phase locking you need something like a COSTAS receiver or equivalent. For detail on one approach to this download and read the Symmetricom 5120A manaual.
Bruce iov...@inwind.it wrote: > In order to simplify the project, and given that I wouldn't need to > distinguish > what source the noise comes from, I could use only S1 and X sources. And here > is > my last question. If I don't lock the sources to one another (say two HP > 10811), > what is the unconvenience? An additional signal in the spectrum, or something > else > that I don't figure now? > > Thanks and kind regards, > > Antonio I8IOV > > >> Some have commercial phase noise measurement systems like Symmetricoms >> 5115A, 5120A. 5125A. >> Some have older HP phase noise measurement systems like the 3048A etc. >> The rest of us have to build our own systems based around sound cards or >> surplus spectrum analysers together with the necessary mixers, low noise >> amplifiers etc. >> >> Unless your sources are very noisy you wont be able to measure their >> phase noise with just a selective voltmeter or even an RF spectrum analyser. >> If you cant build it, then you need to acquire something like the HP3048 >> or the NIST phase noise measurement box currently on ebay.(Item: >> 260423038423) >> >> Bruce >> > > > _______________________________________________ > 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.