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Discussion of precise time and frequency measurement

TrueTime/Symmetricon XL-AK date reset failure

Joe Pendergrass

Mon, Jan 2, 2017 10:29 PM

Hello, all. I am a new member, having discovered this forum a few days ago,
whilst doing a Google search looking for current telephone contact
information for TrueTime/Symmetricon technical support.

For many years I've had a TrueTime/Symmetricon Model XL-AK GPS time &
frequency receiver in service here, which drives multiple serially slaved
9-digit LED IRIG-B remote readouts spread around my station. They display
the day-of-the-year [counted up from 1/1] and the satellite GMT time. At
midnight on each January 1st, the display always updated to reflect the
coming of a new calendar year, and the day-of-the-year on the remote
displays would reset to "0" [Zero]. On 1/1/2016, I noticed that the day
counter display did not automatically reset to zero, and start over. The day
counter display continued increasing incrementally, until 139 days ago, it
finally reset itself to zero and started incrementally increasing again from
[day] 1. Which means that the day-of-the-year counter function currently
reads "139," when it should read "2." The time display has always remained
accurate. I had hoped the day counter issue would resolve itself at midnight
on 1/1/2017; but nothing changed.

I know that the TrueTime/Symmetricon XL-AK and XL-DC GPS receivers are
popular, and now that I have discovered this forum; I would like to solicit
feedback as to what the root of the problem is and how to remedy it, from
anyone on the forum having personal experience with this line of GPS
receivers. Ideas???

Thanks de Joe-W6VI

Hello, all. I am a new member, having discovered this forum a few days ago, whilst doing a Google search looking for current telephone contact information for TrueTime/Symmetricon technical support. For many years I've had a TrueTime/Symmetricon Model XL-AK GPS time & frequency receiver in service here, which drives multiple serially slaved 9-digit LED IRIG-B remote readouts spread around my station. They display the day-of-the-year [counted up from 1/1] and the satellite GMT time. At midnight on each January 1st, the display always updated to reflect the coming of a new calendar year, and the day-of-the-year on the remote displays would reset to "0" [Zero]. On 1/1/2016, I noticed that the day counter display did not automatically reset to zero, and start over. The day counter display continued increasing incrementally, until 139 days ago, it finally reset itself to zero and started incrementally increasing again from [day] 1. Which means that the day-of-the-year counter function currently reads "139," when it should read "2." The time display has always remained accurate. I had hoped the day counter issue would resolve itself at midnight on 1/1/2017; but nothing changed. I know that the TrueTime/Symmetricon XL-AK and XL-DC GPS receivers are popular, and now that I have discovered this forum; I would like to solicit feedback as to what the root of the problem is and how to remedy it, from anyone on the forum having personal experience with this line of GPS receivers. Ideas??? Thanks de Joe-W6VI

Greg Troxel

Tue, Jan 3, 2017 1:21 AM

I have had an XL-DC at work since about 1997, serving as a reference
clock for an NTP stratum 1 server. My memory is getting fuzzy, but at
some point (after I called and asked) Truetime mailed me at no cost a
new ROM of some kind and a tool to cahnge it to deal with the W1K bug.
I think that just changed the default assumption ("time could not be
before X") to a later date. Since then, it has been mostly ok, but
occasionally troubled. Manual date entry allowed me to have it continue
to track. It's on a UPS, so it doesn't see power interruptions, and at
this point has probably been on continuously for ~7 years.

I have not been in the office for a while. I'll follow up privately if
it's ok, or on-list if it's troubleed.

I have had an XL-DC at work since about 1997, serving as a reference clock for an NTP stratum 1 server. My memory is getting fuzzy, but at some point (after I called and asked) Truetime mailed me at no cost a new ROM of some kind and a tool to cahnge it to deal with the W1K bug. I think that just changed the default assumption ("time could not be before X") to a later date. Since then, it has been mostly ok, but occasionally troubled. Manual date entry allowed me to have it continue to track. It's on a UPS, so it doesn't see power interruptions, and at this point has probably been on continuously for ~7 years. I have not been in the office for a while. I'll follow up privately if it's ok, or on-list if it's troubleed.