[ntp:questions] how do I lock in average frequency correction
cswiger at mac.com
Sun Feb 12 23:11:37 UTC 2012
On Feb 12, 2012, at 2:52 PM, Richard B. Gilbert wrote:
> Rather than cooling the crystal it's customary to to put the crystal in an "oven". This is not the oven usually used for cooking. What it does is to heat the crystal to a temperature that can be maintained 24x7 and will be a little warmer than the highest temperature that can be expected naturally. A value in the range 120 to 130 degrees F could be used.
A crystal intended for "oven" use as an OCXO tends to be SC cut and seems to target a temperature of around 200F/90C, but is not very good at room temperatures and is not well suited for TCXO.
The crystal on a motherboard is very likely to be AT cut, be most stable around 30C, and works reasonably well as a TCXO. These will give better timing if the system temp is kept stable and not too hot.
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