[time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

[Jim Lux]

On 12/8/15 3:31 PM, Bob Camp wrote:
> Hi
>
> Let’s see:
>
> EFC uses reference out of the OCXO.
> EFC comes on the OCXO at no added cost.
> 16 bit DAC costs ~$2 to $5
>
> Total cost for EFC setup $2 to $5. Net result is a system with
> spurs that are how ever far down you wish them to be. (It’s all
> about grounding in this case).
>
> Bob
>

If the OCXO has steering, the Q of the resonator has to be lower than if 
the OCXO wasn't steerable.

So conceivably (if such things were available) you could get a 
non-steerable OCXO with better (very) close in noise.

And then move the frequency with the DDS.  It's fairly straightforward 
to make a DDS circuit that pushes the spurs and such away from the 
carrier (at the expense of higher noise farther out).

But hey, that's brand new and exotic.