Any ideas? Plotter outage.......

[TimfromMersea]

Had a curious experience on Saturday. My Northstar 557 plotter wouldn’t find position. It was showing that it was ‘seeing’ 8 or more satellites, but that they were ‘not used in fix’. The AIS and all other functions of it were working fine.

I simply couldn’t get it to find position. I power cycled it seven or eight times, did two ‘factory resets’ from the setup menu, restarted the GPS twice, turned the EGNOS feature off and on again, and when we got back to the mooring, left it for an hour or more to see if it would work when static. Nothing at all.

Then on the boat again Sunday, turned it on - and within a minute, plotting position! And it worked all day. Yesterday, just the same - found itself within a minute and worked fine all day.

It actually did exactly the same thing on one day last year as well.

Can any of ‘my learned friends’ on here shed any light on what might have caused this?

I wondered if, as a relatively old GPS set, it’s more vulnerable to interference than newer ones? There were lots of loud bangs from the Foulness ranges, which are really close to Mersea waters. Perhaps ‘they’ were experimenting with jamming GPS signals?? They’d never admit to it, would they..........

I’d be very grateful if anyone could shed any light on this, or has even perhaps experienced the same sort of issue.

Thanks in advance.

 

[prv]

Perhaps ‘they’ were experimenting with jamming GPS signals?? They’d never admit to it, would they..........

"They" do it from time to time in Scotland (where there are fewer people to be inconvenienced), and don't just "admit it" but publish it in Notices to Mariners so that people can take precautions.

I don't know what's up with your plotter but I doubt it's deliberate jamming.

Did you see if your phone could get a position at the same time? I expect it could.

Pete

 

[TimfromMersea]

I’m aware of the publicised tests in Scotland and points north, and the N to M advising of them. I still wonder if there’s ‘other things’ happening at Foulness, that no one is told about.

The iPhone did find position, but iphones use the Russian GLONASS system as well as GPS, and also triangulate themselves by using the cellphone masts, so it would have been surprising if it hadn’t.

 

[robertj]

I had exactly the same problem on Saturday aswell mine is a Lawrance in the cockpit. After half an hour it fired up.
I wouldn’t put it past the military or that plotter struggled on first fire up. No problems since

 

[TimfromMersea]

That’s really interesting! Someone else with the same problem, on the same day.

Military? Satellite outages? Kim Jong Un’s electromagnetic pulse device?! Doubt we’ll ever know.........

 

[mlines]

How long since it was last used prior to this event?

If it has been a while then the Almanac could be corrupted or lost (internal battery flat?) or just way out of date. To get a new almanac you need to have a steady, uninterrupted view of satellites for a minimum of 15 minutes. Any loss of signal during this time will extend the time it takes to get a new almanac. I have seen up to 30 minutes on our old Northstar after winter storage.

The Factory resets will have certainly cleared the almanac and then started the long download process to get a new one from a passing satellite

 

[TimfromMersea]

I don’t think it was that as it was working fine only a few days before, and after the winter layup from early November, it started in early April with no problems.

 

[NickRobinson]

I got similar symptoms when my Garmin 128 needed a new button cell.
It would show satellites greyed out but take ages to lock. Routes vanished and the time defaulted to years ago.