Yeah, that was totally it: http://www.thegleam.com/ke5fx/spur_demo.gif
The spur amplitude accuracy is at its best in the red trace, just before the LNA starts to distort. Martyn: see if the amplitude of the spur you inject has any effect on the apparent inaccuracy of the 3048A. LNA misbehavior could still be affecting your measurement, even though you're not looking at an FM'ed source. Alternatively, try the same measurement without the 3048A's LNA switched in, if you can? -- john, KE5FX > Ah... that could very well be the case. The second lobe is so > weak relative > to the first, that it's very easy to believe that harmonics > generated in the > LNA were stronger. I'll bear that in mind when re-checking the > measurement. > Sounds like another win for Occam. > > -- john, KE5FX > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > > Behalf Of Bruce Griffiths > > Sent: Thursday, January 17, 2008 5:11 PM > > To: Discussion of precise time and frequency measurement > > Subject: Re: [time-nuts] PM-to-AM noise conversion > > > > > > John > > > > A simpler and more prosaic cause is distortion in the post phase > > detector amplifier. > > If this amplifier sees enough of the modulation frequency fundamental > > component, > > it could conceivably produce enough second harmonic by itself to produce > > the observed effect. > > _______________________________________________ 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.
