Hi The noise spectrum is composed equally of AM and PM noise. Together they add to -174.
Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Graham / KE9H Sent: Tuesday, January 15, 2013 3:46 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Thermal noise contribution to phase noise Bruce: The last time I looked, the thermal noise floor was still -174 dBm/Hz (at 300 Kelvin). http://en.wikipedia.org/wiki/Thermal_noise Are you saying Boltzmann's constant is off by 3 dB, or are we mixing apples and oranges here? Is there a 3 dB adjustment between noise floor (at room temperature) and the "single side band" phase noise measurement, which only looks at half the noise, since it only looks on one side of the reference signal? --- Graham / KE9H == On 1/15/2013 1:38 PM, Bruce Griffiths wrote: > I've noticed a disturbing tendency to quote the thermal noise > contribution to phase noise as -174dBm/Hz instead of the corrent value > of -177dBm/Hz as verified by measurement by NIST: > http://tf.nist.gov/phase/noisemeas.html > > This error occurs in papers from Spectrum Microwave, Wenzel Associates > and others. > Blindly propagating the results quoted in the early literature isnt > particularly helpful given that the definition of SSB phase noise has > changed in the intervening decades. > > 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.