> > Really scratching my head now. I understand why the SSB filter makes a > > difference, because the mirror image of the FM spur is > coherent. I don't > > understand why the 11729C's view of this DSB measurement (11.5 > MHz, 30 kHz, > > first lobe) is closer to 'correct', while the earlier one (20 > MHz, 1 kHz, > > second lobe) was ~6 dB too high... > > > > -- john, KE5FX > > > > > > > John > > In the case of coherent FM the phases of the LSB and USB first lobe > components when translated to baseband are the same. > Consequently their amplitudes add. > The phases of the USB and LSB second harmonic (of the modulation > frequency) lobes differ by 180 degrees when translated to baseband so > that the 2nd harmonic of the > Thus their amplitudes subtract.
Hmm, I didn't know that. Wouldn't that effect have suppressed the 2nd lobe almost entirely on the baseband measurement, though, rather than making it appear 6 dB too high? I should probably repeat that measurement to make sure of what I'm doing. Much appreciate the advice, by the way! -- john, KE5FX _______________________________________________ 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.
