[time-nuts] OCXO and fluctuations after EFC adjustment

[Hal Murray]

richard at karlquist.com said:
> At this time, I will give my usual speech about IMHO the fact that since the
> invention of the DDS on a chip, EFC should no longer be used  for high
> performance oscillators. 

That caught my attention.  Could you please say more.

A DDS introduces spurs.  They move around as you change the adjustment 
parameters.

Are the spurs small enough that they are not a problem with most applications? 
 What applications do/don't get along with spurs?

What do spurs look like on an ADEV plot?

I think of a "DDS on a chip" as having a VCO/PLL up to some fairly high 
frequency and some digital logic that brings that down to the target 
frequency.  The high frequency means that the time step from N to N+1 cycles 
is smaller.  But VCOs are noisy relative to a good crystal.  So in addition to 
spurs, I'd expect more phase noise.

Am I on the right track?  What should I have asked?


-- 
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