[time-nuts] Low-long-term-drift clock for board level integration?

Peter Monta pmonta at gmail.com
Mon Feb 20 05:19:22 UTC 2012


> ... but then they get taken indoors and plugged into the network, and probably never get a clear view of a GPS or GLONASS satellite again.

A high-sensitivity GPS receiver might still give useful results here,
especially if it has a high-quality reference oscillator like an OCXO.
 Even 20 or 30 dB of path loss from roof to your device might be
manageable.   Of course, your deployment environment could well be
worse.

Since you get an initial fix outdoors, you could tell the GPS unit its
location, then put it in "time-only" mode, which needs only a single
usable satellite.  This is the usual mode for timing receivers.  If
the number of satellites drops to zero, though, an OCXO will not hold
over for long inside a 10 microsecond window.

Cheers,
Peter



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