[time-nuts] Re: pulling some crystals

[Bob kb8tq]

Hi

When you change the oven temperature you get both first and second order temperature effects. You also impact the degree aging has “settled out”. 

The turning point on your crystal is going to be a “that depends” sort of thing. A 20C range is not unusual, even on a crystal built to put in an OCXO. 

One question that has not been asked: Are these in cold weld or resistance weld packages? If these are resistance weld then the aging stuff about cold weld parts simply does not apply ….

Bob

> On Dec 11, 2023, at 6:31 PM, glen english LIST <glenlist at cortexrf.com.au> wrote:
> 
> thanks Rick, Bob
> 
> which said aging going both directions..... If i can going to drive temperature  on the crystal to deal with this IE board temperature will be between 30deg C and 60 deg C, then I am going to have a tough time dealing with this  . IE having the crystal live between 60 deg C and say 100 deg C.
> 
>  But  aging direction is not absolutely known.  The  angle of the cut etc needs to be chosen to cover all the bases, and this just might not be possible.
> 
> groan.  Remember, this doesnt have to be super stable- it will be pulled against a 10 MHz TCXO or GPS in the system.
> 
> Look at (one of ) the charts, something that has a turning point (TP) of 70 deg C would be - 15ppm at 70C and + 15 ppm at 110 C ... or if _/- 10 ppm is enough, -10ppm at 60 C and +10ppm at 100C.
> 
> etc.
> 
> <aiB0rIBoE64q23WT.png>
> 
> 
> 
> 
> 
> On 12/12/2023 1:18 am, Richard (Rick) Karlquist wrote:
>> Great summary Bob. 
>> 
>> Just wanted to amplify your point about the "dominant effect" syndrome. 
>> When I was young and foolish 50 years ago, I believed the folklore 
>> about Colorado Crystals "magic" glass enclosures:  unlike "dirt