[time-nuts] oscillators
Bob Camp
lists at rtty.us
Sat Sep 1 15:32:58 UTC 2012
Hi
Observing a curve and being able to compensate it are often two different things. Hysteresis is one very obvious example. Another is simple sensor lag. A some what less obvious one is that the temperature performance is also influenced by the rate of change in temperature.
Here's another thing to consider:
If your crystal is running 3 ppm / C, and you are after 3.0 x 10^-11 stability at one second - You will need to either have a rate of change at ~ 1x10^-5 C/sec (0.6 mC / min) or you will need to compensate for some pretty small changes. That of course makes a bunch of assumptions ….
Bob
On Aug 31, 2012, at 11:26 PM, Jim Lux <jimlux at earthlink.net> wrote:
> On 8/31/12 7:16 PM, Bob Camp wrote:
>> Hi
>>
>> Ok, that gets you back to the basics of really major delta F / delta T slopes.
>>
>> Bob
>>
> yeah.. but as long as you know what the curve is.. the NCO has a huge range (after all, we already have to tune over >500 kHz...a few hundred Hz isn't a big deal.
>
>
> A more complex problem is doing insitu calibration from, e.g., GPS signals or from some externally received frequency reference. (since the radio in question can also work as a GPS receiver, eventually).
>
>
>
>
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