General > General Technical Chat
Does anyone play with GPS based ntp server and have clients?
tkamiya:
Thank you. I didn't even think of that.
tkamiya:
With my previous setup, both GPS and PPS would go to "X" state. Often times immediately, sometimes an hour or so later.
So, I made several changes.
1) replaced GPS
2) shorten the pps and data serial cable
3) play with offset a little
12 hours later, I got this:
remote refid st t when poll reach delay offset jitter
===================================================
*SHM(0) .GPS. 0 l 1 16 377 0.000 -9.225 5.857
oPPS(0) .PPS. 0 l 15 16 377 0.000 0.000 0.001
<more sources here>
This is how it should be, correcct?
ve7xen:
--- Quote from: tkamiya on December 14, 2021, 03:47:09 pm ---With my previous setup, both GPS and PPS would go to "X" state. Often times immediately, sometimes an hour or so later.
So, I made several changes.
1) replaced GPS
2) shorten the pps and data serial cable
3) play with offset a little
12 hours later, I got this:
remote refid st t when poll reach delay offset jitter
===================================================
*SHM(0) .GPS. 0 l 1 16 377 0.000 -9.225 5.857
oPPS(0) .PPS. 0 l 15 16 377 0.000 0.000 0.001
<more sources here>
This is how it should be, correcct?
--- End quote ---
Looks fine, assuming the offset to your other sources is reasonable and ntpd hasn't marked them all invalid because they don't agree with your prefer source.
tkamiya:
Offset used for GPS (local)
server 127.127.28.0 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.0 time1 0.032 flag1 1 refid GPS
fudge will require further tuning.
none of other sources are "X"'d out.
jav:
Looks great.
Don't bother too much with the GPS offset (and the fudge factor). As long as it's around those levels, it's fine. ntpd will use PPS as a reference, that's what is for.
Key here is that the values keep in that range so ntpd don't falsetick ("x") them out.
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