I've been interested about synchronizing clocks using GPS signals and have been wondering if the cheap GPS receivers (Fastrax uPatch100) I have are any good in this respect. Their data sheet lists their PPS (1 pulse per second) output accuracy as 50 ns RMS, which is 50 ppb (that is 50*10^-9 relative error). The aging rate of the oscillator in the 1992 is specified at 3 ppb/day. The accuracy of the PPS output would thus seem to be adequate for determining whether calibration is required.
|Fastrax uPatch100 GPS receiver with a DC/DC converter to power it from a lithium battery. The coax carries the PPS signal.|
|The GPS receiver had to be placed outside to get a signal. The coax goes back inside and connects to the frequency counter.|
|Racal-Dana 1992 showing the period error. Here the PPS output is measured as being 23 nanoseconds longer than a second (or what the 1992 considers to be a second).|