I think Yigit meant your OWN atomic clock, such as a Rubidium standard oscillator. I have several of them and they are awesome but I got mine used from eBay. They are about $100 used but that is no good for an actual production part supply. My guess is that they are in the $2K USD range new. They are rated for a 10 year continuous operating life. The life is limited because they contain an RF-excited Rubidium lamp and the Rubidium slowly diffuses into the glass envelope and eventually there is no longer enough of it left to produce sufficient light for the system to operate. Depending on the level of accuracy you need, Bob, and the cost you can tolerate, an ovenized crystal oscillator which is disciplined to GPS, could work. With the loss of GPS, you could probably get something like 3 seconds per year accuracy (0.1 ppm). I have an old used banged-up fluke signal generator here which has a built-in ovenized crystal oscillator as its reference. It was manufactured in the mid to late 1980s and it is only off by about 30 ppb (0.03 ppm or 1 second per year) when I compare it to my Rubidium standard. Sean On Fri, Apr 19, 2013 at 6:51 PM, Bob Axtell wrote: > On 4/19/2013 6:36 PM, Yigit Turgut wrote: > > Hey Bob, > > > > Try atomic clocks, they are precise and independent of gps. > > > > Actually, I have, but I plan to sell these trackers worldwide, and WWVB > has distance > limitations. It does OK in northern South America, but won't reach > further down. Europe > is covered va Swiss, German and UK time servers. Anybody know their > range of coverage? > > --BA > > > > > YT > > > > > > On Sat, Apr 20, 2013 at 1:11 AM, Bob Axtell wrote: > > > >> My need is precision time, nothing else. Before GPS, ships navigated > >> knowing the time > >> and the sun angle. I know where I am at, so with a precise clock, I ca= n > >> obtain the sun angle. > >> > >> It seems to me that there would be little reason to shut the time > >> service off, which only needsONE > >> bird. > >> > >> --Bob A > >> > >> On 4/19/2013 7:27 AM, RussellMc wrote: > >>>> This came up in a conversation related to solar tracking. Will the > >>>> military shut off > >>>> ALL of the GPS services, or just positioning, during a wartime > footing? > >>>> > >>>> How about time/date services? > >>> First casualty is to change to "selective availability" > >>> Accuracy drops substantially. > >>> This was the mode the system ran in fr many years when first > introduced. > >>> AFAIR this was done for 'Desert Storm'. > >>> > >>> I do not know if it is done, but you could shut it down regionally so > >>> that a portion of the globe was without service. How small and well > >>> defined you could do this would be "interesting". > >>> A very determined person could gain useful information from two > >>> satellites and possibly from one. > >>> > >>> Russia operates a GPS system (GLONASS*) that (memory says) uses polar > >>> elliptical orbit satellites as in that orbit shape they are in the > >>> high poleward part of their orbit for the majority of the time. > >>> Usefulness diminishes as you go southward. If they transmit around th= e > >>> whole orbit you MAY get some use from low altitude satellites in the > >>> southern hemisphere. > >>> > >>> > >>> > >>> Russia > >>> > >>> ___________________ > >>> > >>> http://en.wikipedia.org/wiki/Satellite_navigation > >>> > >>> http://en.wikipedia.org/wiki/Global_Positioning_System > >>> > >>> Says: > >>> > >>> Initially, the highest quality signal was reserved for > >>> military use, and the signal available for civilian use was > >>> intentionally degraded (Selective Availability). This changed with > >>> President Bill Clinton ordering Selective Availability to be turned > >>> off at midnight May 1, 2000, improving the precision of civilian GPS > >>> from 100 meters (330 ft) to 20 meters (66 ft). The executive order > >>> signed in 1996 to turn off Selective Availability in 2000 was propose= d > >>> by the U.S. Secretary of Defense, William Perry, because of the > >>> widespread growth of differential GPS services to improve civilian > >>> accuracy and eliminate the U.S. military advantage. Moreover, the U.S= .. > >>> military was actively developing technologies to deny GPS service to > >>> potential adversaries on a regional basis.[18] > >>> > >>> __________________ > >>> > >>> GLONASS > >>> > >>> http://en.wikipedia.org/wiki/GLONASS > >>> > >>> iPhone 4S, iPad Mini and HTC provide GPS & GLONASS > capability. > >>> > >>> GPS and phone baseband chips from ST-Ericsson, Broadcom a= nd > >>> Qualcomm support GLONASS in combination with GPS. > >> > >> -- > >> > >> The only place success comes before work is in the dictionary. > >> > >> VINCE LOMBARDI > >> > >> -- > >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > >> View/change your membership options at > >> http://mailman.mit.edu/mailman/listinfo/piclist > >> > > > -- > > The only place success comes before work is in the dictionary. > > VINCE LOMBARDI > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .