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Old 07-05-2012, 16:05   #1
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lost GPS fix

Pulling into an anchorage that I've been to lots of times this weekend my GPS lost its' fix. Was all bummed out and checked the connections etc to no avail. Turned it off and back on; nothing. So I figured maybe it will come back the next day when time (you know that dream type thinking) to leave and all I was out was my anchor alarm.

Next day turned it back on and still no fix. So I figured it is the receiver and I'll screw around with it later since I know the way home (and I can read a chart).

But as I motored out the fix came back right about where I had lost the signal going into the little cove!!!

This is just an abandoned island with northing on it, no antenna etc.

Anyone else ever seen this?
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Old 07-05-2012, 16:17   #2
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Re: lost GPS fix

It's most likely the GPS is on its last legs. Many units fail after 4-6 years, mostly due to the internal battery failing.

Before they fail completely they often become intermittent.

Car thieves are useing gps jamming equipment, but these effects are very localised. The military can jam GPS signals over a wider area, but it does not sound the location where either of these two problems would be seen.
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Old 07-05-2012, 17:02   #3
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I experienced a loss on a garmin 4208. The nmea connection/ backbone was in the engine room . I moved the connections out of the engine room routing them to cabin space fwd of the bridge deck. Seemed to work since. That was a year ago. I have my antenna mounted below deck but flush with a otherwise clear path above deck. I like this as the antenna is protected. Other then that failure it's been flawless. I don't have faith in gamins nmea connection. Every wire is tied tite as it enters the branch connection.
I hooked up an ok'd 492 and as back up but it never happened again. Event was at night c and d canal
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Old 07-05-2012, 17:11   #4
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Re: lost GPS fix

Quote:
Originally Posted by Don Lucas View Post
.........Anyone else ever seen this?
Yes, occasionally, do you have a discrete external antenna; IME these fail before the GPS receiver does and usually start becoming intermittent well before a hard failure occurs.

How old is the receiver?
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Old 07-05-2012, 17:21   #5
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Re: lost GPS fix

I figure that system is 10-12 years old (came with the boat last year).

I do have an external antenna. My last boat had a Garmin and the antenna went bad once and I replaced it so I know that happens (but it never came back once it went bad). Current boat is a Raymarine but the antenna is basically the same mounted on the aft rail.

I noticed last year that if someone put their hand on the antenna long enough that I would lose signal.

It was just weird that the unit lost and regained the signal at about the same spot, both of which were pretty open. But maybe just a coincidence.
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Old 07-05-2012, 17:42   #6
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Re: lost GPS fix

If it is a Ray, the internal battery can be replaced.

b.
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Old 07-05-2012, 18:10   #7
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Re: lost GPS fix

I have 2 chart plotters and both lost fix connected via seatalk to 1 antenna; does this change the possibilities?
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Old 07-05-2012, 18:16   #8
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Re: lost GPS fix

Quote:
Originally Posted by Don Lucas View Post

This is just an abandoned island with northing on it, no antenna etc.

Anyone else ever seen this?
Sure have.

Perfect place for a gubment installation.

If they are there, they are there to help you.


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Old 07-05-2012, 18:27   #9
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Re: lost GPS fix

LOL IM from the Goverment and Im here to help ya !!! I really doubt the Gov had anything to do with this ! Im sure one of the above reasons is the cause of your problem! Altho I have found a FEW Places where signals seem to fade and even go away !! I found a place in Belize last yr when we went in to anchor up same as you describe! the signal came back the next day and have had no other problem with the hand held since! Hope yours is alright !(I also have a back up that did not work either so maybe it was a signal drop !) I don't know as Im still not to sure how all this stuff works LOL
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Old 07-05-2012, 18:48   #10
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Quote:
Originally Posted by Don Lucas
I have 2 chart plotters and both lost fix connected via seatalk to 1 antenna; does this change the possibilities?
It points to items that are common to both plotters. In your case that sounds like the antenna and the wiring.

A backup system should be as independent as possible such as a handheld or iPhone or iPad.

Also when troubleshooting it is nice to try and repeat the fault. I probably would have been so curious that I would have immediately gone back in the cove.

The Bad Elf and the XGPS150 that I have for the iPad both have nice monitoring apps where the individual satellite signal strengths can be determined.
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Old 07-05-2012, 19:53   #11
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Ha, and some people make fun of us folks who still have a sextant aboard
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Old 07-05-2012, 21:03   #12
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Re: lost GPS fix

Ahh I carry a sextant, but Ive never needed it to anchor!! LOL but i would sure miss my depth finder !! Just kiddin
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Old 08-05-2012, 04:42   #13
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Re: lost GPS fix

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Originally Posted by gpdno View Post
Ha, and some people make fun of us folks who still have a sextant aboard

Thanks, that helps answer the question
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Old 08-05-2012, 07:38   #14
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Re: lost GPS fix

Quote:
Originally Posted by Don Lucas View Post
Pulling into an anchorage that I've been to lots of times this weekend my GPS lost its' fix. Was all bummed out and checked the connections etc to no avail. Turned it off and back on; nothing. So I figured maybe it will come back the next day when time (you know that dream type thinking) to leave and all I was out was my anchor alarm.

Next day turned it back on and still no fix. So I figured it is the receiver and I'll screw around with it later since I know the way home (and I can read a chart).

But as I motored out the fix came back right about where I had lost the signal going into the little cove!!!

This is just an abandoned island with northing on it, no antenna etc.

Anyone else ever seen this?
How small was the cove and how tall was the surrounding terrain? If the some or most of the satellite constellation is/was blocked your system could/would loose lock, particularly so if the soil also has a high iron content. I have seen this while hiking with our handheld and, at least in theory, the same could happen aboard, no?
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Old 08-05-2012, 07:45   #15
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Re: lost GPS fix

my garmin 2010 had a similar problem replaced the antenna works well now
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