[time-nuts] GPS Usage
jimlux at earthlink.net
Wed Mar 9 16:45:01 UTC 2011
Lots of people use GPS for timing because it's cheaper or more
convenient in a budgetary sens than alternate approaches. Here at JPL,
it's easier, in general, for me to put a GPS timing receiver and GPSDO
in a lab than it is to try and run cables from the "house sources".
The latter requires involvement of more facilities folks and "touching"
more organizations (e.g. the people who "send" the signal, the people
who "maintain" the wires or fiber, etc.), many of whom will have some
sort of continuing charge (which is reasonable.. they ARE providing a
service), for which you need a valid charge number.
Putting a GPSDO in a lab requires a one-time purchase and a one time
facility request to put the antenna in.
We did a bit of an informal trade a few years back to look at 4
alternatives for a half dozen labs in our building.
1) Distribute frequency standard and derived time code from JPL
Frequency/Timing Lab (the "maser")
2) Install a single GPSDO, and distribute the frequency reference and
3) Install a single antenna, splitter, and install a separate GPSDO in
4) Install multiple antennas and GPSDOs, one set for each lab.
the latter is the most flexible, and has the smallest "individual
increment" cost (i.e. there's no "capital improvement" going on)
Given the plethora of GPS antennas sprouting from the tops of buildings
around here, I suspect others have made similar analyses.
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