Puzzling clock offset spikes

Hal Murray hmurray at megapathdsl.net
Sat Jun 30 07:26:36 UTC 2018

What's in your ntp.conf?

You might try increasing any maxpolls if they are less than 6.  It's likely to 
make the normal case worse, but if the spikes get better that might tell 
you/us something.

Do you have full logging?
  logfile /var/log/xxx
  logconfig =syncall +clockall +peerall +sysall

There might be something interesting in there.

You might try putting all the log files into a memory file system.  Maybe the 
disk writes are disabling interrupts long enough to cause troubles.  Or try a 
USB hard drive.

If you run out of other ideas, try without gpsd.  Use the NMEA and PPS drivers.

> I have a thin, closed-cell insulation sheet  affixed to the back of the GPS
> hat to slow temp variations coming from  the Raspi itself

The temperature of the GPS isn't important.  Time comes from the crystal that 
drives the CPU.  I think it's on the bottom of the board.

These are my opinions.  I hate spam.

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