Yes, Bob did warn me but I decided to try anyway.
I measured the ADEV of a cheap VC-TCXO in the past starting starting
with a tau of 1 second and the ADEV nicely started around 1e-10, well
within the required spec. But there was a hint there where some
stability issues depending on the Vtune so I measured the ADEV starting
at much smaller tau (starting at 50ms) and the relation with the Vtune.
The results where remarkable, to say the least and, can be seen using
this link: http://athome.kaashoek.com/time-nuts/TCXO%20Vtune.png
Ignore the rise of the ADEV with larger tau as the very large capacitors
used to get rid of any ripple or noise where still (dis)charging
As long as the Vtune was below 0.5 Volt the ADEV at tau=50 ms measured
about 1.5e-10 (yes, I confirmed using a very stable OCXO that the used
frequency meter can measure the ADEV with this resolution and short tau)
But as soon as the Vtune got above 0.5 Volt the ADEV at 50 ms started to
rise and at Vtune of 1.5 Volt the ADEV was 3e-9
Looking at the frequency deviation there clearly is some repetitive
active switching in the TCXO, no clue what.
Now I need to find a cheap TCXO that behaves a bit better, although, the
ADEV at tau of 1 s was still well within my target spec but one can hope
to find something better
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe send an email to [email protected]
