[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

[Lux, Jim]

On 6/12/22 6:30 PM, Bob kb8tq via time-nuts wrote:
> Hi
>
> Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For
> bonus points, open up the crystal package. If you have the gear to test it, take a look
> at what the gas *is* inside the package. ( Good luck with that :) :) :) )
>
> If you had the gear and the willingness to scrap out OCXO’s you would find that a number
> of fast warmup OCXO’s have a *tiny* amount of He in the package. Measuring this would
> be tough ( it’s that small). Go through the thermal modeling and it’s *way* more conductive
> (thermal wise) than a *perfect* vacuum ……
>
> Bob


And the worst thing is that if your vacuum sealed widget is in an 
atmosphere with more He around (like waiting for a launch, in a place 
that does more He leak tests, etc.), the He will diffuse into your 
package and it doesn't work like expected.