If the two positions are fixed, say a permanent VLBI or bi-static radar
installation, You can do pretty well (say < 5 ns delta between sites) with
GPS-steered cesium. The long-term stability of the delta can be even
better (say < 1 ns). Even with civilian one-way GPS, the cesium allows you
to average the position/time with averaging times of days. Once locked, you
have the short-term stability and phase noise performance of a good cesium,
with long-term phase and frequency accuracy driven by the GPS constellation.
Historically, there have been several off-the-shelf GPS-steered-cesium
solutions, there was an option board for the TrueTime XL-DC, which steered
the 5071A, and the Datum 6801, which steered the FTS 4040/CsIII series.
There was even a short-lived product, the Datum Cs+, which crammed it all
into one box. Alas, all of these products are out of production, but you
may find them on the used market.
-RL
------------------------------------------------------------
Robert Lutwak, Senior Scientist
Symmetricom - Technology Realization Center
34 Tozer Rd.
Beverly, MA 01915
(978) 232-1461 Voice [EMAIL PROTECTED] (Business)
(978) 927-4099 FAX [EMAIL PROTECTED] (Personal)
(339) 927-7896 Mobile
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