Right, he wasn't making assumptions about Martyn's case, necessarily, but addressing my assumptions about sideband coherence.
-- john, KE5FX > Here I go again. Martyn defined how he was generating the 100 Hz > beat note. > So, not much to assume in this case. - > > > > Mike B. Feher, N4FS > 89 Arnold Blvd. > Howell, NJ, 07731 > 732-886-5960 > > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Bruce Griffiths > Sent: Thursday, January 17, 2008 4:46 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] PM-to-AM noise conversion (was RE: New Question > onHP3048A Phase Noise Test Set) > > John Miles wrote: > > I see what you mean, Bruce, but why are the two sidebands considered > > incoherent, just because they're noise? Since the IF is 0 Hz, the other > > sideband appearing at the analyzer input jack is a folded image of the > same > > noise spectrum, right? Given that, shouldn't the SSB > correction be -6 dB > > rather than -3 dB? > > > > > The phase angle between the USB and LSB noise components is random when > translated to baseband so when averaged over time the resultant > amplitude is the same as if one just added the powers of the 2 components. > When the 2 sidebands are coherent the phase shift between them is fixed > so that their amplitudes add (vectorially). > The phase angle between the LSB and USB components when translated to > baseband depends on the modulation mechanism creating them. > With both LSB and USB components translated to baseband one has no > additional information so that some "reasonable" assumption has > to be made. > > Bruce > _______________________________________________ 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.
