You hit the nail on the head so to speak:
[root@NTP ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
xGPS_NMEA(0) .GPS. 0 l 15 16 377 0.000 495.991 0.016
*admin.non-stop. 203.35.83.242 2 u 44 64 77 0.446 0.319 0.164
130.220.30.32 .STEP. 16 u - 64 0 0.000 0.000 0.000
chronos.ise.can .STEP. 16 u - 64 0 0.000 0.000 0.000
+ns1.unico.com.a 203.23.237.200 3 u 14 64 377 28.897 -1.359 7.578
+ntp.hiltech.com 149.20.64.28 2 u 10 64 377 87.497 4.514 13.151
GPS initially was selected but eventually got marked as false ticker.
I am going to drag a silly scope down there to have a look at the timing pulse,
I have a vague suspicion it maybe inverted by the rs422-rs232 convertor which I
built. Although unrelated to this issue, I came across this today while
building a 'gadget box' for a trimble acutime:
TTL out of rs422 convertor goes into the max232 like this :
__
_______| |___________
But the rs232 comes out of the max232 inverted, like this:
_______ ____________
\__/
The slew rate on rs232 is not so good for timing is it ):
Mark
-----Original Message-----
From: Dave Hart [mailto:[email protected]]
Sent: Saturday, 4 February 2012 4:00 PM
To: Mark C. Stephens
Cc: [email protected]
Subject: Re: [ntp:questions] timing issue with a HP 58534A
On Sat, Feb 4, 2012 at 03:04, Mark C. Stephens <[email protected]> wrote:
> I put that in because without noselect I get this:
>
> [root@NTP ~]# ntpq -p
> remote refid st t when poll reach delay offset
> jitter
> ======================================================================
> ========
> xGPS_NMEA(0) .GPS. 0 l 4 16 377 0.000 0.931
> 0.012 xtime.non-stop.c 210.9.x.x 2 u 61 64 377 0.340
> -496.02 0.236
>
> [root@NTP ~]# cat /etc/ntp.conf
> #
> #keysdir /etc/ntp
> keys /etc/ntp/keys
> trustedkey 1
> requestkey 1
> controlkey 1
>
>
> # GPS NMEA
> server 127.127.20.0 mode 16 minpoll 4 maxpoll 4 fudge 127.127.20.0
> flag1 1 # time2 -0.400
>
> # GPS PPS
> #server 127.127.22.0 minpoll 4 maxpoll 4 prefer #fudge 127.127.22.0
> flag3 1
>
> #Inhouse reference
> server 192.168.5.8 iburst maxpoll 9
>
> logconfig =allall
> driftfile /etc/ntp/drift
> enable stats
> statsdir /var/ntp/stats
> statistics loopstats peerstats clockstats
>
> Both are now false tickers. Could it be this GPS gumming up the works?
It appears despite my claim, fudge time2 -0.525 or so is needed for NMEA to
properly associate the PPS with the correct second. Moreover, you're running
into the "man with two watches never knows what time it is" problem -- there's
no tiebreaker if there's disagreement. Add more network sources, and/or
"noselect" all sources except NMEA, at least until you get NMEA behaving well.
Cheers,
Dave Hart
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