[time-nuts] Bye-Bye Crystals

[Dan Kemppainen]

Hi Bob,

If one prototypes any crystal oscillator, and runs it on a bench. Then 
builds an 'oven' of sorts and runs it on the same bench. Would you 
expect to see any improvement?

In other words for a given oscillator (crystal and electronics, etc), 
will there be any improvements in an oven compared to not in an oven? 
Or, are there other things that outweigh the gains by temp controlling 
the whole thing.

Yeah, this is a pretty open question, but I don't really have a feel for 
how good an oscillator needs to be before an oven starts to improve 
things...

Dan




On 3/15/2017 12:00 PM, time-nuts-request at febo.com wrote:
> Hi
>
> Where do you plan on getting an OCXO grade crystal at an odd frequency like
> that? Much of the performance of a good OCXO is in the crystal. Doing a proper
> design on one is a lot of work. You *might* think that having a design for 5.000000
> MHz would give you a good design for 5.000050 MHz. I have empirical evidence that
> this isn’t the case. Many years later, I’m still utterly amazed that this is the way things
> work in the crystal business ….( = it’s not just a design issue, it’s also a business decision)
>
> More or less the crystal needs to be:
>
> 1) Cut specifically to have a turn at a temperature that makes sense for your application.
> 2) A “large blank” design (for it’s frequency)
> 3) In a cold weld package (most of the normal crystals are resistance weld)
> 4) Run through a high vacuum / high temperature process
> 5) Be plated with gold rather than something like silver or aluminum (unless it’s at VHF).
> 6) Have a motional capacitance that makes sense for your EFC range ( normally = minimize)
> 7) Preferably be an SC or modified SC cut.
>
> This is for a high stability part. The list does keep going on for a while, but that should
> give you a pretty good idea.
>
> Bob