Electronics > Metrology

Synserver S200 GPS lock question

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ki0kn:
Hello all,
I've been searching/reading this forum for days now (as a guest) and decided to join and ask about this since I am running into a dead end.

I have a Syncserver S200 that's been running great for a long time.  I bumped some cabling in the rack the other day and it went into alarm with a GPS antenna open error.  I found that the BNC center pin had splayed a bit and wasn't making contact.  I rectified this and it rebooted and it found the GPS.

After approximately 20 hours, it changes from Survey to Position hold, has a good position.  GPS lock is "Unlocked'.   I am trying to figure out if I have the Sept 2022 problem with my GPS but am not sure how you determine this. 
Here's the info screen:

Local Time
Sunday January 08 07:49:42 2023 MST
Hostname
CizekNTP1
 
NTP Stratum
3
NTP Reference ID
108.61.73.243
 
Current Sync Source
NTP
Status
Locked
 
GPS Receiver Status
Position Hold
Number of Satellites
4
 
Alarm Status
No Current Major or Minor Alarms
 
Model
S200
Release Version
1.30
Up Time
1 day(s) 12 hours 12 minutes

I do have the 1.36 image and the HDD raw imaging tool (and a delkin card).  I could try the 1.36 upgrade if that has any merit, but I suspect that maybe my GPS has the rollover problem maybe?

Just trying to determine why I can't get lock.

Thanks for any assistance, I've been learning (turning from education to pulling hair out!!) for some days on this, but the only piece I can't find data on is how to determine if your GPS has the issue.  If it does, I assume the easiest fix is to replace the GPS with a new board that doesn't have the issue?

James

miro123:
Only four satellites.
Do you have the RSSI levels?

ki0kn:
3   -159   Current
4   -159   Current
7   -156   Current
9   -150   Current
16   -162   Current


It varies because of the shadowing of the antenna... but I see typically 5-6 usually and up to 8 at a time.  How many do you need for a "lock"?  It's been locked for months and has had as many as 8 and as little as 3 visible that entire time.   I watched it go from 2d solution to 3d solution within an hour of reboot and it's been in the state it's in now every time since.

Thanks!
James

ki0kn:
You got me thinking about the number of satellites.  I added an extension cable to move the antenna out in the clear open.

4   -155   Current
7   -152   Current
8   -151   Current
9   -149   Current
14   -159   Current
20   -162   Current
27   -153   Current
30   -155   Current


8 satellites in view now, full position fix, it's in "position hold" and still will not "Lock"

Wondering if there are other ideas?

Thanks.

James

The Bootloader:
Hi,

GPSDOs may need hours, if not days, to lock.
I would recommend you wait it out for one more day or two, and come back to report
Very important to not touch ANYTHING during that time, and ensure the receiver has a clear view of the sky during this time.

Additionally, how long is your extension? An extension which is too long can cause problems. Some GPSDOs have an option to compensate for this.

(I have a GPSDO myself)

Also, side note, the "Sept 2022" problem you mention can happen at any date. GPS week number rolls over every 1024 weeks, and GPS receivers all have a reference date in their firmware. Usually, this is the firmware build date, but can be older too. The GPS receivers work for 1024 weeks after this reference date without further information. But after that, they get a wrong date, and this can lead to issues like you mention. Some GPS receivers have a command to send them a new reference date.

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