[time-nuts] OCXO and fluctuations after EFC adjustment

[Gerhard Hoffmann]

Am 11.04.20 um 00:33 schrieb jimlux:
> On 4/10/20 2:31 PM, Richard (Rick) Karlquist wrote:
>
>>
>> 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.
>>
>> Rick N6RK
>
> Yes..
>
> The only case I can think of is where the oscillator is being directly 
> multiplied up and one cannot tolerate the spurs from a DDS.  There are 
> folks who believe that this is the case for generating the downlink 
> carrier in a deep space transponder.
>
> However, I believe that even in that incredibly niche application, one 
> can design a DDS to have minimal spurs in the area close to the 
> carrier. In fact, just today, a transponder on Bepi Colombo makes a 
> close approach to Earth on its way to Mercury that implements just 
> such a scheme.
>
> I can conceive that there might be an application where the "move the 
> spurs around" approach wouldn't work or would be too complex.
>

I can only hope that my FE405 from the group buy from some years ago is 
not typical

of the spur performance. I could not decide which spur to move, and where.

OTOH output power is lowish and on the ADEV side it dives quite deep 
into E-13 land

which speaks for its free-running osc. Measured with a customer's E5052B.

(Yes, I have opened and inspected it, but there are no low-hanging fruit.)


Cheers, Gerhard DK4XP



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