[time-nuts] Low-Cost Rubidium Performance

[Javier Herrero]

El 10/02/2012 00:13, Javier Herrero escribió:
> El 09/02/2012 22:28, Magnus Danielson escribió:
>>
>> Consider that it is de-modulated and then low-pass filtered.
>>
>> Also, it is the alternating rate and not 1400 Hz difference in DDS 
>> setting which is the key parameter here. The 1400 Hz gives a hint of 
>> the Q-value however, which seems to be lower on these than on any of 
>> my larger rubidiums, but it is maybe to be expected.
> Yes, you're right... I was thinking on the alternating rate (that in 
> fact I measured, at 416.6666..Hz, but the other number came first ;) 
> ), and in the fact that the FRS, that uses 127Hz as alternating rate, 
> has notorious spurs at 127 and 254Hz (al at a lot of their harmonics), 
> so I was expecting someting similar for the FE5680A at 416.6666Hz and 
> harmonics, but seems not to be there (or the spur forest makes not 
> easy to see these trees :) )
>
I answer myself. Perhaps they are there quite notoriously, since in the 
spectra plots that I took when I got mine, now it is clear why there are 
two peaks at around -70/-75dBc at somewher that seems very near 
+/-416.7Hz: http://www.nebulosa.org/images/FE5680A/FE5680A4.jpg Probably 
in the phase noise plot they are masked by all the phase noise floor and 
other spurii that are not so apparent in a quick measurement with the 
spectrum analyzer

Regards,

Javier