[ntp:questions] how do I lock in average frequency correction

Richard B. Gilbert rgilbert88 at comcast.net
Mon Feb 13 17:54:14 UTC 2012

On 2/13/2012 2:36 AM, Dave Hart wrote:
> On Sun, Feb 12, 2012 at 19:03, Chuck Swiger<cswiger at mac.com>  wrote:
>> On Feb 12, 2012, at 9:36 AM, unruh wrote:
>>> The clock crystal ages, and suffers internal crystal "cracks"
>>> migrations, etc, which change the frequency of the crystal. Thus even in
>>> a temperature controlled oven, the crystal frequency will change, but
>>> much of the crystal frequency change is driven by temperature changes.
>> Agreed, temperature swings will have a major impact on the crystal frequency.
> Well, I know what you're saying but we're talking on the order of 1
> PPM / degree C.
>> You might be able to improve the stability of the crystal by ensuring good
>> airflow and cooling via HVAC as needed.  And I suppose you could adjust the
>> rate by changing the HVAC set-point, but I don't think the benefit is worth it.
>> I'd be more likely switch to an OXCO + GPS on a PCI/PCIe card if such as needed.
> That's OCXO, oven controlled crystal oscillator.  Why X for crystal?

Crystal is frequently abbreviated as XTAL.  I think this usage may have 
originated in amateur radio.


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