AIS drop out

All_at_Sea

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Hi I have a Raymarine AIS 650, transmit and receive, running through an e90w chart plotter. On sailing along the coast over the weekend the AIS plots kept dropping out. On re-booting the chart plotter they came back briefly but soon disappeared again.

The AIS is showing a green light, l have two aerials on top of the mast, one for VHF and one for AIS. I have the latest software. What's going on? Could it be that l have switched the two aerials? All seems fine in harbour but once underway it starts to be problematic......any help gratefully received. What else onboard could cause interference? I'm thinking the VHF radio as l don't always sail with this on, could this be the problem?
 

RichardS

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Is it a recent problem? If so, have you changed anything recently?

I suspect that having two aerials so close together with the VHF radio on might well cause a problem but you can easily test this by leaving the VHF off.

Richard
 

ex-Gladys

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Firstly, I have no experience of Seatalk and Raymarine, but if I was looking at this I would first check that data is consistently getting to the plotter. I don't know what diagnostic capabilities there are on your plotter. On my Garmin 751 I can do a NMEA diagnostic and see that the appropriate NMEA sentences are being delivered to the plotter. I had an issue when I originally installed, as the instruments (also connected to NMEA) kept on dropping off the plotter, and I could see that the sentences weren't there. The ultimate issue was my VHF NMEA transmit connection (for transmitting DSC data back to the plotter), which for some reason interfered with the instruments.

I would think that's more likely than physical interference on VHF channels, after all AIS and VHF signals are designed to coexist....
 

pvb

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On the instructions for the Comar unit we have it says that the antennas must be at least 5 meters apart, I would suggest you try as Richard says above.

Comar recommend a 2 meter vertical separation between the transceiver and VHF/DSC antennae. The 5 meter separation you quoted is for the transceiver's GPS antenna.
 

KevinT1

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Hi I have a Raymarine AIS 650, transmit and receive, running through an e90w chart plotter. On sailing along the coast over the weekend the AIS plots kept dropping out. On re-booting the chart plotter they came back briefly but soon disappeared again.

Not sure if this will help, but you can plug a Laptop in and run the diagnostics for the AIS650 when it is working and connected to the Seatalk / Plotter - that will show if it is transmitting, receiving and if there is a problem with the aerial ( VSWR etc ) .

Kevin
 
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