unruh wrote:
On 2010-04-18, David Lord <[email protected]> wrote:
Hi
I just noticed that the GPS used as reference for my xtal oscillator
clock source has from midnight last night been losing reach. Previous
24 hr to that logging at 6 minute intervals had all 240 entries
at 377 but now they are mostly at 0 or start increasing for a short
period, last up to 76, then drop back to 0. Any chance this is due
to atmospheric volcanic ash?
I sort of doubt it, unless the ash is conductive.
David
I'd had 48hr with all sources at 377 throughout since last
change. I withdrew that post within a minute or so of posting
once I saw reach on my xtal clock had also been lost at about
same time. I think there is some interaction (bug) between
the different refclock sources that's been fixed in more
recent sources (I can't so far get these to compile on NetBSD).
I had this setup
GPSb 127.127.20.0 using gps0 => tty00
PPSb 127.127.22.2 using pps2 at ppbus
OSCc 127.127.22.0 using pps0 => tty00
I've restarted with xtal oscillator OSCc moved to parallel port
and PPSb from GPS moved to serial port.
GPSb 127.127.20.2 using gps2 => tty00
PPSb 127.127.22.2 using pps2 => tty00
OSCc 127.127.22.0 using pps0 at ppbus
and it looks ok again:
remote refid st t when poll reach delay offset jitter
========================================================================
+GPS_NMEA(2) .GPSb. 0 l 63 64 377 0.000 0.004 0.004
oPPS(2) .PPSb. 0 l 6 16 377 0.000 0.001 0.004
PPS(0) .OSCc. 0 l 3 16 377 0.000 -186.94 0.088
-k6x400 158.152.1.76 3 u 12 64 377 1.215 0.144 0.517
+me6000g .MSFa. 1 u 63 64 377 0.754 -0.103 0.560
-p4x2400c 192.168.59.64 2 u 24 64 377 1.247 0.841 0.540
I'm busy at moment getting circuit for xtal oscillator oven
worked out. Best open air xtal has done is 10ms change over
24hr but tonight it's drifting about 6ms per hour. Temperature
has varied since 11th from mid 20s to 12C or below so I'm
reasonably confident I'd get better than 1ms/day holdover
with even a crude temperature control. I'm using much same
circuit as for my beer brewing box but that has a 500W heater
element pwm via an opto isolated triac.
cheers
David
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