[time-nuts] A new take on the all-hardware GPSDO concept

Bob Stewart bob at evoria.net
Mon Sep 12 17:00:51 EDT 2016


Nick said:
"Jim Miller's 10 kHz GPSDO that’s been referenced here has either solved this problem, or the 10 kHz output of the Jupiter is substantially better than the Venus’ 10 MHz output, or the design doesn’t give the results time-nuts expect from a GPSDO. Which of those applies?"
Hi Nick,
You have to be very careful about the receiver you select.  I think it's the case that the Jupiter's internal oscillator is phase locked to the GPS signal.  In that case, you can use the output from the receiver to directly drive a PLL giving a high quality 10MHz or whatever you like.  But, the low cost receivers on the market now, including those from Ublox, do not phase lock their oscillators to the GPS signal.  In the case of Ublox, they specifically say that the quantization value is only available for the 1PPS output.  So, yes, you can get a 10KHz pulse train from a Ublox or any other modern inexpensive GPS receiver, but it will suffer from whatever quantization error the manufacturer specifies.

bob
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