Invalid Fix

[Deleted User YDKXO]

Both plotters on my boat have suddenly started flashing invalid fix warnings. They're both connected to the same aerial. From satellite window it seems that the aerial can 'see' a good number of satellites but can't get a good fix on any of them. Have checked all connections and all seem OK. Do GPS aerials fail? Anybody suggest anything else I should check?

 

[DAKA]

Friend had a problem like this with a garmin years ago.

The gps thought it was in southern hemisphere and couldnt interpret the signals.

From set up tell the gps you are in Singapore/China or anywhere a long way away.

let it get lost there and then tell it you are back in the UK and it should find itself .

 

[hlb]

Yep, your ariel can fail with no warning. IT seems any arial will work, it dont have to be rathion.

 

[MapisM]

Anybody suggest anything else I should check?

Did you check if another GPS works properly? Frinstance a portable one, as in many modern mobile phones.
In Croatia (and nowhere else, so far!), I experienced twice a total GPS failure.
The 1st time, it just lost the fix, as it seems to happen to yours.
The 2nd time, it thought I was cruising between 200 and 300kts in random directions.
Normal operation was restored after leaving the area where that happened.
My guess was that there was some local interference causing the erratic behaviour.
It happened once in the Kvarner channel, and the other time much further south, but can't remember where exactly.

 

[RobHom]

I've had one or two act up over the years.... What I did was get out the manual and ran them through the setup/initialization process all over again. That seemed to take care of it.

This may seem an odd question....but is there any chance that the units have been moved more than 100 miles while turned off? If so that will cause them to not get a fix worth a plugged penny. They have to be reinitialized then.

One other little ditty.... If your antenna for the GPS has an external mechanical connection.... try taking it loose and cleaning it with a Q-tip (cotton tipped toothpick thingy) dipped in rubbing alcohol. Sea air can cause a coating on the contacts that will foul signal transmissions.

 

[noelex]

Both plotters on my boat have suddenly started flashing invalid fix warnings. They're both connected to the same aerial. From satellite window it seems that the aerial can 'see' a good number of satellites but can't get a good fix on any of them. Have checked all connections and all seem OK. Do GPS aerials fail? Anybody suggest anything else I should check?

Yes they do fail. Most often from the internal battery getting low. A backup GPS that can be quickly switched as an input to the chartplotter is very helpfull.
So now you have to buy 2 new GPS units