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km4ack / pi-scripts

Various scripts written for ham radio pi
GNU General Public License v3.0
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remove 500 ms delay in gps install #13

Open km4ack opened 4 years ago

km4ack commented 4 years ago

Discovered something else. In /etc/chrony/chrony.conf there's an entry that sets the parameters of the reference time source NMEA.

refclock SHM 0 offset 0.0 delay 0.8 refid NMEA

I set the offset on that line to 0.0, it was 0.5 and that put my station within 100ms of most stations using only GPS as a time source.

As I understand it, setting that to 0.5 (500ms) is intended to make the NTP servers more preferred by Chrony when connected to the internet, basically an intentional 500ms error. Removing that offset gets the pi clock set very close to NTP server pool time. In a system set up for very accurate time off grid, I think that offset of 500ms should not be set.

from email with John Schultz

joshuajayg commented 4 years ago

I have also noticed a 500-600ms time drift from other stations when operating FT8/JS8. I always operate off grid. It does not seem to affect performance but if it is possible to remove, I believe it should be.