plotter losses signal on certain sail headings

[smeaks]

I have noted on here that several posts champion the virtues of the internal receiver family of plotters - myself included! However I find that my Navman 5505i looses the gps fix from time to time. At first I thought it could be a power drop but new leads and connections have not cured this. It is mounted on the hatchway beneath the sprayhood. I have been analyising the problem and think it occurs mainly when beating up wind ie with the boom in tight. Is the boom/sail adding to the interferece and blanking the set from seeing the satelites? Has anyone else found this? I have not founda setting on the plotter (upwind mode!) that can can!

 

[ga1135]

Ha Ha, I have the same situation like you, install the antenna of my Navman 5505 under the boom.

The plotter prompt warning signal for lossing fix whenever I tack (the boom goes over the antenna) and require a crew to press the "Ent" botton to release the alarm, which is very inconvenience.

I once wanted to move the antenna to somewhere else but unable to find a better place than the current protected location.

Somehow, I de-activated the "DGPs" function and the alarm never prompted again. The fixings showed on the plotter seem OK and no problem.

You may consider if de-activate DGPS function can suit your need, or you may just try before making long term setting.

Cheers. /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif

 

[alan]

If it was a power drop I would expect the plotter to re-set itself and not just lose the satellites?
Experiment with the boat in the berth: move the boom out of the way, check how many satellites are visible and their positions, move the boom into a close-haules position and see of tou lose any/all of the satellites. Try this a few times, at different times of the day with the satellites in different positions.
It could be that the boom is causng some sort of multi-path effect, and when there are only two or three satellites visible and in use by the receiver, it could cause a drop.

Alan.

 

[oilyrag]

If it's the same problem I had with a 5500 it is incurable because the service centre cannot identify the problem - it's a GPS time/positional issue so running it on the bench for a zillion years will never recreate the problem because the set is static.
Long boring saga with mine but in the end I got an exchange unit from Navman that worked faultlessly. Suggest if it is still in warranty you take it back and get a new one. If the supplying dealer is not keen get in touch with Navimo who should exchange it.

 

[lw395]

You should think about how much worse the signal might get when your sprayhood is doing its job, running with salt water as you beat into some real weather. Your gps is clearly marginal in relatively fair conditions. I would not be happy with that. Does your backup handheld gps get a good signal when held next to the plotter? i.e. is the shading of the aerial/multipath that bad or is the plotter 'deaf'?
It may be worth eliminating interference as a (contributory?) cause, switch off absolutely everything else, particularly mobile phone chargers and see if it helps.
A GPS should generally have quite a bit of margin at the moment as the satellite power levels are higher than spec. Anything that doesn't work well given a reasonably clear view of the sky isn't fit for purpose, imho.
Will it accept external nmea pos'n data? If so you can sometimes get Garmin GPS35's or similar quite cheaply- an external antenna/receiver with nmea output, just no display etc.
Sorry to tell you what you don't want to hear, but better now than when your crew lose confidence because the gps won't work (been there!).
Cheers
Chris

 

[Nick_Pam]

[ QUOTE ]
If it's the same problem I had with a 5500 it is incurable because the service centre cannot identify the problem - it's a GPS time/positional issue so running it on the bench for a zillion years will never recreate the problem because the set is static.
Long boring saga with mine but in the end I got an exchange unit from Navman that worked faultlessly. Suggest if it is still in warranty you take it back and get a new one. If the supplying dealer is not keen get in touch with Navimo who should exchange it.

[/ QUOTE ]

I had a "similar" issue on a Raymarine C80, although it only happened when the boay was stationary in the berth - NEVER when sailing...

Was identified as a software/firmare problem connected with the "Differential" part of the DGPS signal occasionally losing time-lock and was fixed in the next version of Raymarine firmware now installed in later models.

Not sure that the subject of this post is down to satellite sighting problems as most GPS's these days will "see" through fibreglass cabin roof, let alone sprayhood canvas - more likely a software/firmware glitch in the unit as Oilyrag says.

 

[Haven't-a-Clue]

I don't know much about sailing but I suspect the boom swinging across the antenna may well be a primary cause. I say this 'cos one day when I was driving down 17th street in downtown San Diego, my GPS must've picked up a reflection from one of the skyscrapers as it indicated for about 2 seconds a speed of 323.6 mph! /forums/images/graemlins/grin.gif Just a thought, I could be (and probably am) wrong.