Loss of GPS position in recent days (24/7/06)

[Gin]

Do you remember this problem from previous posts?

Well, truth to tell I haven't yet followed up Oldhand's pointers but will certainly check the unit's mode when I reinstall it.

I sent the offending unit back to Raymarine, who have bench tested it for days and it has performed with a clean bill of health- I am awaiting its return as I write.

The engineer's report was read out to me and the conclusion is that either the power, or interfacing cabling(either the Seatalk circuit or the NMEA circuit) is/are the culprit(s), or even the aerial which is a small Raymarine domed job sitting on the pushpit which I haven't knocked so far as I recall.

I rerouted the Seatalk cabling over winter so this could be the cause BUT I did not interfere with the power supply to the RN300 nor did I disturb the NMEA cabling which feeds the cockpit repeater- yet the repeater showed"No Input" on each occasion the DSC went into an alarm condition. So I don't think it is my work which has created this situation, and I did first make enquiries as whether the unit could feed NMEA and Seatalk simultaneously

Clearly I need to hook everything up again and pay greater attention to what then happens but it seems to me that unless this was an intermittent unit failure or cabling problem then the only other source must be the aerial.

Does this make sense??

How do I test the aerial without going to the expense of buying a replacement- and if a replacement is necessary must this be sited in a vulnerable position outside or can it be fixed under deck somewhere??

 

[Talbot]

My GPS aerial failed recently. I sent it back to navman for repair, and they said it needed replacement. I replaced the SMA plug on the end of the cable and it now works perfectly (£2 repair!)

 

[AIDY]

I had a similar problem a few years back on my raymarine gps. the problem for me was the mushroom dome aerial thingie... it has a battery inside, so i was told which had failed. i sent this back to raymarine they confirmed this and i did a part exchange on a new bit.

 

[Gin]

Ahaaa! You would think that Raymarine would have mentioned that wouldn't you- still never mind.

I've booked a call to speak to their engineers this afternoon( they only take such calls pm)and see where we go from there but I shall first try Talbot's idea of changing plugs as that is the obvious first thing to do.

Many thanks to both of you

Gordon

 

[Bodach na mara]

I lost position several times this year and the problem is the plug. Advice on changing it would be welcome.

 

[old_salt]

See this very good description by DogWatch on replacing BNC connectors if yours is similar it will have the same method of Assembly.
By DogWatch.
I hope this helps.

 

[Birdseye]

[ QUOTE ]
.

Does this make sense??

How do I test the aerial without going to the expense of buying a replacement- and if a replacement is necessary must this be sited in a vulnerable position outside or can it be fixed under deck somewhere??

[/ QUOTE ]

Yes it does it the circuit is aerail to unit and then from there to dsc and repeater.

There is no easy way to check the aerial unless you have a pal with an interest in electronics and equipment to match. Or maybe your local Raymarine dealer will sell / lend you a replace on a sale or return basis? Failing that the cable is the next thing to check. Simple really - looking for a dirty connection or corrosion somewhere. The NMEA signal is a simple volts on / off so the cable doesnt carry much if any current.

Dont just start on replacing bits without reason though. Thats just lashing out.

Doubtful you can put the aerial under deck - the sat signal is very weak and almost anything attenuates it beyond detection. Certainly, even if it worked you would degarde accuracy because you would restrict the sats available.

 

[Bodach na mara]

Thanks David for that link

 

[Oldhand]

RN 300 uses a TNC connector, not a BNC. I had to cut the original off to route the cable and have had no problems with the self installed TNC nor the antenna. I would be very surprised if there is a battery in the antenna, I thought it took DC through the RF cable.

 

[old_salt]

I think the Assembly is somewhat similar I can not just recall to mind right now but if you have the principle of one the other is not to different to make up. My trouble is over the years I have made up so many different types you tend to not think to much about it.

 

[Niord]

No battery in Raymarine domed GPS Ae. I have a failed one replaced by Raymarine (FOC) and stripped it down to see what was inside - simply a circuit board

 

[dulcibella]

My boat has one GPS aerial (part of the system) on the pushpit and another (outputting to the DSC) below the deck. I can't detect any difference in performance between them.

 

[BruceDanforth]

Do you have anything that is connected to the Seatalk Bus but switched off - a tiller pilot perhaps? I have known Raymarine gear do spurious things in this situation.

 

[awyatybw]

Loss of GPS position in second week of August

We had a loss for 3-4 hours in the North Sea off the West Friesland islands. Neither main unit nor handheld (both older types) could find enough satelites to get a fix. I do not reacal the exact day - second week of August.