[time-nuts] OCXO and fluctuations after EFC adjustment

[Bob kb8tq]

Hi

Spurs on an ADEV plot look like ripples in the curve. If you have a part
with good close in phase noise / good short tau ADEV, you probably
can see effects from spurs that  120 db down in the vicinity of 10 Hz. 

Bob

> On Apr 11, 2020, at 4:22 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
> 
> 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?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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