[time-nuts] PPS offset between GPS receivers
lists at rtty.us
Wed Dec 5 12:15:29 UTC 2012
Rather major typo there
Should be - 2 us would NOT come as a big surprise.
On Dec 4, 2012, at 7:39 PM, Bob Camp <lists at rtty.us> wrote:
> 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.
> On Dec 3, 2012, at 11:12 PM, Gabs Ricalde <gsricalde at gmail.com> wrote:
>> 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 1354495734.000000102
>> source 0 - assert 1354495735.000000040
>> When I switch the PPS source to the SKG25A1, the ppstest output
>> indicates the PPS of that receiver is about 2 us early compared to the 58534A:
>> source 0 - assert 1354495740.999997923
>> source 0 - assert 1354495741.999997905
>> The setup looks like this:
>> 58534A GPS -> 10 m CAT5 cable -> MC3486 RS422 receiver -> GPIO
>> active antenna -> 3 m cable -> SKG25A1 GPS -> GPIO
>> Both receivers were factory reset before the test.
>> I'm planning on getting another GPS receiver to check which receiver
>> is at fault. Has anyone found timing differences this large with their
>> GPS receivers?
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