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Old 06-12-2017, 20:49   #1
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GPS Antenna fix issue

This seems to happen more regularly recently.
Can see the satellites (red) but can't get a fix.
Any ideas? New antenna needed perhaps?
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Old 06-12-2017, 21:08   #2
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Re: GPS Antenna fix issue

And heres a picture
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Old 06-12-2017, 21:36   #3
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Re: GPS Antenna fix issue

I don't think your problem is the antenna, (space vehicles seem to have signal level) but it could be locally generated electrical noise. You might try temporarily relocating the antenna to see if that helps it.
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Old 06-12-2017, 23:01   #4
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Re: GPS Antenna fix issue

Quote:
Originally Posted by TreblePlink View Post
I don't think your problem is the antenna, (space vehicles seem to have signal level) but it could be locally generated electrical noise. You might try temporarily relocating the antenna to see if that helps it.
I doubt that.
This is in a large clear space all by itself on the roof of a trawler.
It has worked fine for years in that same location, nothings changed up there.
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Old 07-12-2017, 01:24   #5
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Re: GPS Antenna fix issue

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Originally Posted by Simi 60 View Post
I doubt that.
This is in a large clear space all by itself on the roof of a trawler.
It has worked fine for years in that same location, nothings changed up there.
Has anything underneath the antenna, any new cabling or such?
Has the location of the boat changed?

It is possible you antenna is on the way out but more usually it stops receiving satellites totally.
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Old 07-12-2017, 10:24   #6
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Re: GPS Antenna fix issue


I have had a problem with a older garmin GPS, found I had a older program version, updated my program and seemed to have fixed the problem
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Old 07-12-2017, 11:58   #7
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Re: GPS Antenna fix issue

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Originally Posted by boeing1 View Post

I have had a problem with a older garmin GPS, found I had a older program version, updated my program and seemed to have fixed the problem
I'll investigate that.
This is a Seiwa explorer 3
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Old 07-12-2017, 12:02   #8
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Re: GPS Antenna fix issue

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Originally Posted by Wotname View Post
Has anything underneath the antenna, any new cabling or such?
Has the location of the boat changed?

It is possible you antenna is on the way out but more usually it stops receiving satellites totally.
Nope, nothing new underneath and boat changes location regularly but the plotter does get a fix, then loses itself , then finds itself again.

Opencpn running beside it with a $15 USB antenna sitting inside the wheelhouse has no issues.

Neither do cheap phones and tablets
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Old 07-12-2017, 12:13   #9
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Re: GPS Antenna fix issue

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Originally Posted by Simi 60 View Post
I'll investigate that.
This is a Seiwa explorer 3
May be onto something
I have 2008 dates, not 2010.

How update Seiwa Software
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Old 07-12-2017, 12:41   #10
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Re: GPS Antenna fix issue

If the almanac/ephemeris data is outdated, your GPS will be looking for satellites in times and places where they aren't going to be, which will kill things.

Or the antenna cable or fittings could have taken moisture over the years. Some corrosion in the connnections, or moisture absorbed into the cable (even by pinholes) could easily degrade satellite signals.

Since your picture seems to show 3(?) satellites have been received with no problem, the antenna is working to some extent, as opposed to being totally "broke".

If you are in an area (like the coasts of the US) where there is WAAS or other augmentation of the GPS system, and your receiver is too old to have that, then it may pay to upgrade simply for better performance.
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Old 07-12-2017, 13:29   #11
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Re: GPS Antenna fix issue

Thanks
First thing checked were pins and while they looked fine they got a spray with some electronic contact spray.

East coast of Australia, but when GPS has full signal, it does say WAAS.
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Old 07-12-2017, 15:47   #12
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Re: GPS Antenna fix issue

Quote:
Originally Posted by Simi 60 View Post
Thanks
First thing checked were pins and while they looked fine they got a spray with some electronic contact spray.

East coast of Australia, but when GPS has full signal, it does say WAAS.
Hmmm....

This is tweaking my memory a bit. IIRC (and I may have it wrong) when I got my new Vesper Vision I had some obscure problems with the internal GPS. Seems that there is no WAAS correction in Oz and the receiver was confused by the missing signal(s). In the Vesper, one can disable the WAAS feature, and doing so cured my problem.

My recollection may be distorted, but perhaps this is related to your problem.

Otherwise, the intermittent nature does suggest a bad connection somewhere.

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Old 07-12-2017, 15:48   #13
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Re: GPS Antenna fix issue

Quote:
Originally Posted by Simi 60 View Post
This seems to happen more regularly recently.
Can see the satellites (red) but can't get a fix.
Any ideas? New antenna needed perhaps?
This happened to me A LOT. I had to reset to factory default (hold some keys during startup) and then it worked perfect. Frustrating because I would lose my settings and waypoints.

Since the hard reset would fix it, I figured it must be software, not hardware.

I finally solved the problem for good by selling the boat!
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Old 07-12-2017, 20:28   #14
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Re: GPS Antenna fix issue

Quote:
Originally Posted by Jim Cate View Post
Hmmm....

This is tweaking my memory a bit. IIRC (and I may have it wrong) when I got my new Vesper Vision I had some obscure problems with the internal GPS. Seems that there is no WAAS correction in Oz and the receiver was confused by the missing signal(s). In the Vesper, one can disable the WAAS feature, and doing so cured my problem.

My recollection may be distorted, but perhaps this is related to your problem.

Otherwise, the intermittent nature does suggest a bad connection somewhere.

Jim
Pretty sure you memory is still intact (assuming mine is).

Certainly in 2014, WAAS was not available in Australia and I'm pretty confident to say it is still not - I would have heard about it if it was.

WAAS is a US based subset of SBAS (satellite based augmentation system) and (as I understand it) the Aussie government has never shelled out the dollars to have WAAS extended to our part of the world. There was (is?) talk of of making our own or perhaps doing a GBAS system (ground based augmentation system) that would be available to all but so far - nothing. Of course there are some "private" (i.e. user pays) GBAS arrangements around in Oz just elsewhere.

For the OP, a factory default reset of the receiver is probably a good idea but most default resets will result in loss of user entered data. The problem well could be a software glitch in receiver software rather than an antenna issue.

Someone mentioned an old almanac/ephemeris data maybe present but in all the GPS receivers I have worked on, the receiver downloads the ever-changing almanac/ephemeris data each time it is turned on. The usual evidence of an out of date almanac/ephemeris data is a delay in getting an initial fix after turn on but this usually happens only if the unit has not been used for months or has been relocated to a new location hundreds of miles from where it was last used.
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Old 08-12-2017, 13:09   #15
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Re: GPS Antenna fix issue

How old is old? IIRC there was a widespreda problem, maybe a Y2K problem? where a number of GPS instruments had an issue with date rollover. And if an internal memory was wiped (by a bad backup battery, etc.) that's when a unit would have to start cold-scanning from scratch. Likewise, if any GPS is moved while it is off (flown cross-ocean) it may take quite a while to get an initial fix, since it is using the data from the last position to look for satellites, which of course are in different locations now.

All of which is normal for the equipment, but also normally invisible and forgotten by the users. Should be ruled out though, to be thorough about it.

Old, battery, connections...the simple stuff we mainly ignore.
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