[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik, Kaashoek)

[Erik Kaashoek]

After adding an additional 20dB gain stage the measurements became a bit 
cleaner and the noise floor without a DUT connected became flatter.  Due 
an extra capacitor in the audio path there is some increased drop off 
below 5Hz.

As it was impossible to change the scale of the FFT program used you 
have to subtract 40dB from all measured noise levels!!!!!

Noise level of the PNA without DUT connected : 
http://athome.kaashoek.com/time-nuts/PNA/PN_baseline.JPG
This is NOT the noise of the internal DOCXO as without a DUT connected 
the mixer can not produce any output. Its just the noise of the first 
mixer output opamp, which happen to be at least 10dB better than any 
measured DUT.

CTI OCXO: http://athome.kaashoek.com/time-nuts/PNA/PN_OCXO.JPG
AR60 Rubidium: http://athome.kaashoek.com/time-nuts/PNA/PN_Rb.JPG

10MHz reference output of a Rigol SG: 
http://athome.kaashoek.com/time-nuts/PNA/PN_Rigol_10MHz.JPG
10MHz generated by the same Rigol: 
http://athome.kaashoek.com/time-nuts/PNA/PN_Rigol.JPG
The elevated noise floor due to the DDS is clearly visible.

And the reason why I build the PNA:
Cheap Chinese TCXO: http://athome.kaashoek.com/time-nuts/PNA/PN_TCXO.JPG

Next step is conversion to triple supply