[time-nuts] AN/URQ-13 question How long

[Magnus Danielson]

Hi,

On 2021-03-04 11:15, Hal Murray wrote:
> paulswedb at gmail.com said:
>> But since the units been off for at least 15 years and heavens knows how long
>> before that. Any thoughts on how long it might take to stabilize days weeks
>> months. Its pretty stable as is just wondering. 
> It's an exponential tail.  How stable do you call stable?
>
> What do you have to measure it with?  How stable is your environment?
>
These tails have been measured for years. As long as it is slower than
the application can handle, it becomes only the issue of being "within
range". This is the "aging" period. Environmental may cause more severe
deviation eventually, but a power-down/power-up even cause retracing and
that will restart the process.

So, it ends up being about being acceptably stable, as in not being
annoyingly large anymore.

There is fairly good evidence that crystal oscillators do not have much
of wear mechanisms if done with a bit of care. There is oscillators out
there that has been running 40-50 years in continuous operation. Getting
any atomic clock live that long is more of a challenge, they need to be
serviced because of explicit wear mechanisms. I think the PTB CS2 and
CS3 clocks is the longest operations beam clocks, but they also have
work done on them, and upgrades. We end up discussing some of that in
the IEEE P1193 group on environmental effects on frequency sources.

Cheers,
Magnus