[time-nuts] Venus838LPx-T preliminary testing
kb8tq at n1k.org
Mon Aug 15 21:15:41 EDT 2016
This problem is not unique to the P1PS2. It is the way all of these devices
generate an arbitrary output. They drop pulses from a series to “correct”
the frequency. A frequency counter with a long enough gate time will read
them as being right. A spectrum analyzer will show a *very* different picture.
> On Aug 15, 2016, at 12:07 PM, Nick Sayer via time-nuts <time-nuts at febo.com> wrote:
> I had an opportunity to examine the P1PS2 pin’s output from the Venus838LPx-T. By default it’s a 10 MHz output nominally phase locked to GPS time. It didn’t take more than a second of looking at it on the scope to discover that it’s jittery as hell. My guess is that they’re synchronizing its leading edge once a second (or once in a while?) and letting it free-run from there and then correcting it with a sledgehammer at the next opportunity.
> Certainly it’s not usable as a frequency standard on its own. However, for those who had been using James Miller’s GPSDO design with the 10 kHz output from a Jupiter, there might be something here. I wonder if simply adding a cleanup oscillator to the default output might yield results that were good enough. If not, you likely can configure the output to be 10 kHz instead of 10 MHz and then it would be a drop-in replacement. I’ve not (yet) investigated configuring this module for non-default behavior.
> I think I’ll stick with the design I’ve got, but these modules might represent an alternative to the Jupiter.
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