This does not seem to make sense. No matter what you are measuring it is assumed that the phase noise of the item being measured is greater than the piece of test equipment doing the measurement, else you would not see it. In other words, if it is a spectrum analyzer, then the noise floor of the analyzer has to be less than that of the individual oscillators being measured. So, if that is the case, there is no reason why the oscillator's phase noise cannot be measured directly and then which one is better can be readily determined. If mixing two oscillators together to use the mixer as the phase detector, would mean that the measurements would be made near DC. In the direct measurement, the measurement will be made at 10 MHz, no difference in the spectrum analyzers performance either way. Although as I mentioned before more often than not a good oscillator's phase noise is better than that of the instrument used, hence it is easier to make the measurement after multiplying the UUT up to a higher frequency like 1000 MHz and then using the mixer method. - Mike -
Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jeffrey Pawlan Sent: Wednesday, April 27, 2005 11:20 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Upper limit on phase noise from two oscillators. Yes, the upper limit will be one of your oscillators and it is not possible to know which one. When you have actually made the measurements, don't forget to subtract 3dB from the reading because the noise contribution of the two oscillators is power-additive being non-coherent to each other. 73, Jeffrey Pawlan, WA6KBL _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
