On Wed, Apr 11, 2018 at 11:15 AM, Bob kb8tq <kb...@n1k.org> wrote: > Hi > > > On Apr 11, 2018, at 12:11 PM, Graham / KE9H <ke9h.gra...@gmail.com> > wrote: > > > > Phase noise is (usually) more important than absolute frequency accuracy. > > It’s probably well worth looking into exactly what you are after in terms > of phase noise, > spurs, and stability *before* deciding on a solution. In some cases things > like DDS spurs > are a non-issue. In other cases phase noise at certain offsets is a really > big deal, but at > other offsets … it’s a non-issue. > > I am using the single output Bodnar GPSDO driving a frequency locked Wenzel low phase noise oscillator and using that for my SDR ADC clock. I am using it to take phase noise measurements and it certainly is as good as the references I have available, and matches pretty well with measurements on a $90k phase noise meter.
The Wenzel eliminates far out spurs from the GPSDO. Note that different register values may result in the same frequency output of the GPSDO, but spurs can be very different. For some frequencies and with the right register values, I expect the GPSDO alone may be good enough for an SDR clock, but I have not tried. This is the best I can measure with this setup. I think the ADC noise limits the far out phase noise. Offset Phase Noise (Hz) (dBc/Hz) 10 -96.9 20 -103.0 50 -106.9 100 -109.7 200 -117.7 500 -128.4 1,000 -136.4 2,000 -140.1 5,000 -143.1 10,000 -144.9 20,000 -145.6 50,000 -145.7 100,000 -146.2 1,000,000 -146.6 Regards, Mark W7MLG _______________________________________________ time-nuts mailing list -- firstname.lastname@example.org To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.