[time-nuts] NCOCXO anyone?

Scott Stobbe scott.j.stobbe at gmail.com
Fri Jul 22 12:51:18 EDT 2016


Capacitor matching (Moore's law) has improved for switch-cap designs.

Also depends on the tuning gain, 10 ppm/V would be very demanding versus 10
ppb/V.

On Thu, Jul 21, 2016 at 9:47 PM, Richard (Rick) Karlquist <
richard at karlquist.com> wrote:

>
>
> On 7/21/2016 4:56 PM, Nick Sayer via time-nuts wrote:
>
>> Oh my. That’s a bit more than I was originally considering… What I had in
>> mind was adding a DAC front end to an OCXO so that you could tune the EFC
>> with serial commands rather than analog and calling that a product.
>>
>>
> 20 years ago when HP was working on a so called "smart clock"
> GPS box, they decided to do what you said, use a DAC to
> tune the EFC on the E1938A oscillator.  I
> recommended to them NOT to try to do that, but they
> didn't listen to me.  At that time, it
> was nearly impossible to come up with a DAC, buffer
> amplifier, and voltage reference that didn't degrade
> the stability of the E1938A, which isn't even as stable
> as a 10811.  What you need to ask yourself is:  in
> 2016, can I finally get analog components that are
> an order of magnitude or two better than what was
> available in 1996?  I don't know, without researching
> it.  Certainly, we can't depend on Moore's law coming
> to the rescue.  If anything, that works against analog
> IC's by obsoleting older analog processes.
>
> Also in 1996, phase microsteppers were already legacy
> technology and didn't have a good reputation for spectral
> purity.  Another non-panacea.
>
> Rick
>
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