On Tue, Apr 15, 2014 at 10:09 PM, David J Taylor < [email protected]> wrote: > > [] > Even 1 PPS output seems like a workable starting point, but at the expense of a different and/or more difficult path to get to a 10 MHz reference signal I seek. > > Any advance or pointer to source (reasonable cost, whatever that means!) would be appreciated.
Any GPS receiver with 1PPS is OK. All PPS signals are interchangeable. It is just a 5 volt 1Hz square wave. The raising edge of the wave is right at the "tick" of a new second. The GPSDO is simple too. It counts the cycles of the 10MHz oscillator from one PPS raising edge to the next and it should get exactly 10,000,000 cycles. If more or less are counted the software moves the voltage on OXCO's control pin up or down. Controllers can be more complex, but this much will get you started. The simplest next step is to count for 10 seconds and get to 0.1 Hz then add an interpolator and get to milli Hz If you are going to buy and set up a GPS receiver. The hardest part is the antenna. It is best if it can see the entire sky, horizon to horizon and if it is not near any reflecting surfaces. It is best if the antenna is mounted on a mast on the tallest building but a modern GPS will work if the antenna is playing on the desk near a window. You can connect a computer and get software to plot data from inside the GPS but really all you need to go is apply power and get the PPS. The old Motorola "Oncore" series of GPS is reliable and low cost. The "UT" has a PPS one sigma error of about 50 nanoseconds which is "good enough" they sell for under $20. The current new state of the art version is about $60 or $35 used. Here is an example Motorola-UT-Plus-Oncore-Timing-GPS-Module<http://www.ebay.com/itm/ONLY-1PSC-Motorola-UT-Plus-Oncore-Timing-GPS-Module-1pps-NTP-/301132856857?pt=US_Ham_Radio_Transmitters&hash=item461ceabe19> Be SURE to buy the "timing" version. There are non-timing or navigation versions. Make sure it says "timing" in the description. GPS receivers spew out tons of data but you can ignore it all. All you need is the PPS signal. -- Chris Albertson Redondo Beach, California _______________________________________________ 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.
