[time-nuts] NEO-M8N vs. NEO-M8T

Chris Caudle chris at chriscaudle.org
Mon May 21 17:11:10 EDT 2018


On Mon, May 21, 2018 2:23 pm, Gary E. Miller wrote:
> I look forward to your patch!

My GPSDO doesn't have sawtooth error, so limited interest for me.

How much does one of those u-blox modules cost?

How would  you tell if it made the gpsd performance better?  I think that
question came up a couple of weeks ago,  most of the ways to check time
stability involve hardware test equipment logging electrical signals, and
there isn't a good way to get an electrical signal generated cleanly from
the gpsd software clock.

Is there a way to have a timestamp log from another instance of a PPS
driver (another meaning the first instance is the one in use by ntpd)?  So
you could have a PPS driver log timestamps from a really high quality
input signal, such that any variation in the timestamps was due to the
clock variation and not from the input signal, and then see if the
variation in timestamps was less after adding sawtooth correction to gpsd.
That's the only idea I can up up with off the top of my head to check
whether such a patch would actually improve the clock estimate noticeably.
 In essence this is like trying to build a GPSDO without being able to see
the output of the oscillator directly, so the normal approach to measuring
stability with TICC, counters, phase noise analyzers, etc. doesn't really
work.

-- 
Chris Caudle




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