Hi Andre' that is not my appreciation of how off air standards work. You do
not try to get a lock up in 64 microseconds (one frame). In this case the
PLL is not trying to compensate for poor short term stability. The
short-term stability of the VCO must be excellent. My Droitwich standard can
take up to 20 minutes to reach lock after switch-on. The VCO is a very
stable VXO which still have reasonable performance when the locking signal
disappears. I think you must consider trading time for accuracy. A good PLL
should always have the best VCO you can get to reduce the incidental FM. So
over 10 minutes of nudging it in the right direction (not compensating for
its short term stability) it is easy to see you can get 1000 times (at
least) better performance. As you say there will always be a slight error,
but it can be made vanishingly small.
Cheers de Alan G3NYK
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