Hello, Sunday, November 2, 2008, 6:31:32, WB6BNQ wrote:
W> Hi Yuri, W> Unless you need the longer term stability of an undisciplined Rb source, I think W> you would be better served to get one of the “Timenuts group” Trimble Thunderbolt W> GPS units to use as a home standard. It is available via this page: W> http://www.tapr.org/kits_thunder.html W> and info about the unit is available at this URL: W> http://www.leapsecond.com/tbolt-faq.htm W> Add an external very high quality crystal oscillator locked to the Trimble and W> you will have the same stability of a good Rb source. Most would use a high W> quality Rb source, undisciplined, as a tool for comparing or generating W> specifications of crystal oscillators. Unfortunately, I'm currently living in a place that have problems with good location for GPS antenna. The best place available provides less than 40% of open sky view and a lot of buildings around, lots of reflected signals. No access to roof, security is tightened heavily after 9/11 and terror acts in Moscow, so it is big problem to get access to attics or cellars of residental buildings. I curently have uBlox LEA-5S (SuperSense nav module) connected to this antenna.... Not very promising... Fix is available about 70% of time but drifting heavily (due to multipath?), often I see coordinates about 400-500 m away from real location. I have Motorola Oncore M12+T module as well (purchased it with intention to build GPSDO controller), but (IMHO) it will be nearly useless in such conditions with original W5OJM controller design. I thinked about some FLL implementation where microcontroller constantly monitor output of GPS for T-RAIM solution status and discard measurement cycles that have T-RAIM alarms, restarting cycle once T-RAIM reports good timing solution again... Will be fun project, of course, but will take some time. And it will be a good reason to familiarize myself with new 16-bit PIC24 series... Their cascadable up to 32 bits timers/counters with input capture looks quite promising... -- Best regards, Yuri, UA3ATQ/KI7XJ mailto:[EMAIL PROTECTED] _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
