On Jan 20, 5:37*am, Terje Mathisen "terje.mathisen at tmsw.no"
wrote:
Mxsmanic wrote:
How sensitive are these CSACs to other environmental variables? What about
shock, or position? Are they robust enough to be used in wris****ches and
portable timepieces (disregarding cost)?

Which reminds me: why are there no wris****ches that use GPS just for a time
reference, without the geolocation functions? Or are there? Seems like there'd
be a market for such watches to replace "radio-controlled" watches depending
on WWVB and the like, if the price isn't too high. They wouldn't need a CSAC,
although that would be a nice bonus.

No GPS unit is low-power enough to be used as a pure wris****ch, where a
single button battery is supposed to last for years.

You might get away with a very good crystal plus a GPS that only wakes
up once (or a few times) per day or so, in which case you have made
yourself a very expensive chronometer. :-)

Instead of spending power on an oven for a TCXO you could use the Garmin
approach of a tiny temperature sensor (_very_ low power) plus an
automatically calibrated temp adjustement table for the XO.

Terje

--
- Terje.Mathisen at tmsw.no
"almost all programming can be viewed as an exercise in caching"

Military CSAC applications include field radios and soldier automation
platforms that require temperature, shock tolerance anyways.
Even if CSACs don't make it to your typical individual GI equipment,
one should expect them to make it to special forces and other elite
units and platoon level systems. In Afghanistan alone, GPS clock
coasting is extremely desirable for accurate targeting in mountain
riddled terrain. Notice that was the trigger behind the last 24+3 GPS
constellation improvement.
Even if this first generation clock isn't fully able to handle
significant shock, you can be sure someone is working on it. You can't
put it on special forces gear unless it can handle a great deal of
shock.

Marcelo