I'm now using the SKG25A1 as a PPS source for an NTP server. Aside from
the offset, I noticed a large offset jump in the NTP loopstats
(attached) occurring about once a day. This is not the server oscillator
drifting since the frequency graph looks good at this point and this
behavior can
On Tue, Dec 11, 2012 at 5:55 PM, David J Taylor
david-tay...@blueyonder.co.uk wrote:
Gabs,
I've seen similar jumps, and it happens when the GPS/PPS signal drops out
for a while. In my case, the GPS receiver is sitting just in an upstairs
room, not near a window or the root (as I normally
From: Gabs Ricalde
[]
David,
I forgot to thank you for your helpful site and NTP plotter.
I have the antenna outside with a 180 degree view of the sky, outages
should be rare. Looking at the loopstats, the outage during the 4 us
jump is about 12 seconds. This is a test server, I only have the
On Tue, Dec 11, 2012 at 8:00 PM, David J Taylor
david-tay...@blueyonder.co.uk wrote:
From: Gabs Ricalde
[]
David,
I forgot to thank you for your helpful site and NTP plotter.
I have the antenna outside with a 180 degree view of the sky, outages
should be rare. Looking at the loopstats,
I'm not sure about the jammer but I'm running a timing receiver in
position hold several floors up, I haven't seen dropouts like this.
ntpd is running with a noselect NMEA source since I'm having problems
with ntpd marking the PPS and NMEA as falsetickers. The startup sequence
for the server is
Date: Fri, 7 Dec 2012 22:28:20 -0500
From: Bob Camp lists at rtty.us
Hi
A lot depends on exactly what the interrupt structure is. It may also depend
on the phase of the cpu clock relative to the pps signal. What's reasonably
sure is that there is indeed some offset between the two where
Yes, this is a good test: to evaluate how your preferred uP can perform as
a time interval counter, you can hook two GPDSOs' PPS to it and see the
result. The best would be to have at hand also a real TIC (HP53132A,
PM6681, SR620 or similar) and compare.
On Sat, Dec 8, 2012 at 4:28 AM, Bob Camp
I use a tee connection and terminated 100 foot (33 m )piece of RG58 coax
for a known delay to the stop pulse.
Don L
Azelio Boriani
Yes, this is a good test: to evaluate how your preferred uP can perform
as
a time interval counter, you can hook two GPDSOs' PPS to it and see the
result. The
OK, I use the two GPSDOs method because I can set the PPS position but the
cable is useful and only one GPSDO (or any other stable PPS source) is
enough.
On Sat, Dec 8, 2012 at 6:53 PM, Don Latham d...@montana.com wrote:
I use a tee connection and terminated 100 foot (33 m )piece of RG58 coax
One more test to try. Connect one PPS signal to both GPIO ports and see
how close to zero offset you get. It would likely be random which gets
read first.
On Wed, Dec 5, 2012 at 5:37 AM, Gabs Ricalde gsrica...@gmail.com wrote:
Hi everyone,
As Tom suggested, I redid the test with less than
Hi
A lot depends on exactly what the interrupt structure is. It may also depend on
the phase of the cpu clock relative to the pps signal. What's reasonably sure
is that there is indeed some offset between the two where the answer is indeed
ft's random. Another thing to check - how wide is the
Hi
Rather major typo there
Should be - 2 us would NOT come as a big surprise.
Bob
On Dec 4, 2012, at 7:39 PM, Bob Camp li...@rtty.us wrote:
Hi
Based on a quick look, the SkyNav does not appear to be a timing specific
part. A 2 us error in a navigation part would come as a big surprise.
Hi everyone,
As Tom suggested, I redid the test with less than 1 ft. of wire from the
PPS output to the GPIO without any logic gates or line receivers. Same result,
the SKG25A1 was 2 microseconds ahead of the 58534A. Without any other way of
testing, I would probably trust the output of the
Hi
Based on a quick look, the SkyNav does not appear to be a timing specific part.
A 2 us error in a navigation part would come as a big surprise.
Bob
On Dec 3, 2012, at 11:12 PM, Gabs Ricalde gsrica...@gmail.com wrote:
I'm using a Symmetricom 58534A GPS timing receiver and a GPS board
Hi
Based on a quick look, the SkyNav does not appear to be a timing specific
part. A 2 us error in a navigation part would come as a big surprise.
Bob
==
Indeed! The PPS output of various navigation parts I've checked recently
have typically been
I'm using a Symmetricom 58534A GPS timing receiver and a GPS board with a
SkyNav SKG25A1 module driving stratum 1 NTP servers.
On one of the servers, the ppstest output while the 58534A is connected
looks like:
source 0 - assert 1354495734.00102
source 0 - assert 1354495735.00040
When I
Hi Gabs, and welcome to the list.
Or, the 58534A is 2 us late compared to the SKG25A1. If you have a 'scope handy
check the risetime of the signal at all points in the long chain from the
58534A to the GPIO.
Better yet, if you have a dual-channel 'scope or TI counter, compare the 1PPS's
as
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