AIS output from M-Tech MT550 Radio

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Mark Turner

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I've bought an M-Tech MT550 DCS VHF radio with AIS to link to my Garmin plotter as being cheaper than an AIS engine and splitter and less effort than installing a second antenna at the top of the mast. On the MT550 there is no display on the radio of AIS signals and not surprisingly (to me) I can't immediately see any AIS plots on my plotter.

Is there an easy way to know whether this is a plotter problem or a radio problem or my fault? It being my fault is the simplest explanation, but assuming I've got the wiring right how do I otherwise attribute the fault? I'm in Portsmouth Harbour and there are always plenty of AIS signals on Shipfinder.

Grateful for any advice, please.

Mark
 
The usual NMEA datastream is at 4800 baud (bits per second).

AIS will be transmitted from the radio as per the usual AIS speed which is 38400 baud.

Have you changed the setting on the input port on the Garmin plotter to be AIS38400 (from the default NMEA0183 - 4800)?
 
The plotter has two ports for NMEA 0183 - one at 4800 which carries GPS data out (for the DSC functional on the radio) and one at 38400 that the AIS input to the plotter uses. I'm pretty sure I've got the 38400 output on the radio linked to the 38400 input on the plotter and all use a common ground.
 
Sorry, I should have been clearer. The MT 550 doesn't have the facility to display AIS data, only to receive it and send it on in my case to my plotter. As I'm not seeing it displayed on my plotter it could be that nothing is being sent, I've got the wiring wrong or it's a problem in the plotter. I wondered whether there was a way to test that the radio is receiving and processing the data.
 
Mark Turner said:
... I've got the wiring wrong or it's a problem in the plotter...
Click to expand...
Wiring or Baud rate are the most likely candidates.

You need to connect the TX wire of the VHF to the RX wire on the plotter, plus the common or ground wires for their respective ports. Surprising how many people forget this.

Can you change the RX rate on the plotter?
 
No, but the plotter Garmin GPSMAP 720 has two ports, one at 4800 for gps and one at 38400 for AIS. I'll have another look at the wiring at the weekend.

Mark
 
The other way to check for output from the VHF is to connect the input of a serial port of a laptop to the 38400 VHF output and using something like Hyperterminal or NavMonPC software (on the laptop), see if anything is being sent over the wires.
 
Martin_J said:
The other way to check for output from the VHF is to connect the input of a serial port of a laptop to the 38400 VHF output and using something like Hyperterminal or NavMonPC software (on the laptop), see if anything is being sent over the wires.
Click to expand...

This is certainly an option that I would use, but it does open up a whole new can of worms for the uninitiated.
 
"Uninitiated" is a succinct, if slightly generous description of where I am at:)
 
Mark Turner said:
I've bought an M-Tech MT550 DCS VHF radio with AIS to link to my Garmin plotter as being cheaper than an AIS engine and splitter and less effort than installing a second antenna at the top of the mast. On the MT550 there is no display on the radio of AIS signals and not surprisingly (to me) I can't immediately see any AIS plots on my plotter.

Is there an easy way to know whether this is a plotter problem or a radio problem or my fault? It being my fault is the simplest explanation, but assuming I've got the wiring right how do I otherwise attribute the fault? I'm in Portsmouth Harbour and there are always plenty of AIS signals on Shipfinder.

Grateful for any advice, please.

Mark
Click to expand...
You won't get any AIS data if the receiver is not supplied with its gps position from the Garmin. (I'm stating the obvious!)
 
ianj99 said:
You won't get any AIS data if the receiver is not supplied with its gps position from the Garmin. (I'm stating the obvious!)
Click to expand...
Since when did AIS receivers need GPS input?
The VHF will need GPS position data for DSC to be send the position if the red button is used..
OTOH AIS Transceivers need it's own dedicated GPS receiver.
 
Mark Turner said:
I've bought an M-Tech MT550 DCS VHF radio with AIS to link to my Garmin plotter as being cheaper than an AIS engine and splitter and less effort than installing a second antenna at the top of the mast. On the MT550 there is no display on the radio of AIS signals and not surprisingly (to me) I can't immediately see any AIS plots on my plotter.

Is there an easy way to know whether this is a plotter problem or a radio problem or my fault? It being my fault is the simplest explanation, but assuming I've got the wiring right how do I otherwise attribute the fault? I'm in Portsmouth Harbour and there are always plenty of AIS signals on Shipfinder.

Grateful for any advice, please.

Mark
Click to expand...

I think you have got most of the relevant tips already
I don't know your equipment but some thoughts.

I think that on most plotters with an high speed NMEA 0183 port the speed is configurable and will probably have low speed 4800 as default, check if there are a setup menu on the Garmin plotter.
Some plotters have a port monitor where you can view the data coming in on that port.
Double check that you have wired correct - Tx from radio to Rx on the Plotter.
The Radio (don't have built in GPS ?) need GPS input for DSC.

Have a look at page 86 in this document regarding "Setting the Communication Format for Each NMEA 0183 Port"
http://static.garmincdn.com/pumac/GPSMAP_700_Series_OM_EN.pdf
 
In this case though.. the Chartplotter that is to be used to display the AIS target information is actually the GPS itself so it will not need supplied position.

The question is though whether or not the radio will actually send out the AIS sentences if it has not itself received GPS position information.

The manual for the VHF does not make this clear.. http://www.watski.se/archives/manualer/M-TECH/English%20MT-550.pdf

It would be useful for the VHF DSC function though to ensure the VHF is receiving position information anyway.
 
If I've got it set up correctly and good connections made, then the VHF should be receiving gps for DSC (and the screen on the radio shows that that is working) and sending AIS, high speed to the high speed port on the plotter. I'll check it all out tomorrow ( at least it puts off anti fouling).

Thanks for all the responses - really appreciated.

Mark
 
Just to say thanks for all the advice -seems to have been a wiring problem (i.e. I'd wired it wrongly)as suggested in several posts.

Mark
 
Mark Turner said:
The plotter has two ports for NMEA 0183 - one at 4800 which carries GPS data out (for the DSC functional on the radio) and one at 38400 that the AIS input to the plotter uses. I'm pretty sure I've got the 38400 output on the radio linked to the 38400 input on the plotter and all use a common ground.
Click to expand...

Did you check that the plotter is set up to receive the sentence as transmitted by the radio for AIS....(NMEA VDM sentence at 38400 bps.)


I am a bit puzzled as when I try to find a manual for the GPS 723 I get sent to the GPS 720 Series page and the GPS 720 does not seem to have a 34500 port???
only 4800 However the GPS 723 does???

Watch this..Its where you should get to.

https://www.youtube.com/watch?v=ubTPxreO8mc&index=10&list=PLvaHV4hle1SsHnHEA_jfd_GxUoGPPHNb9


I would double check your wiring and also make sure that the AIS port in the plotter is activated.

I take it the AIS connections are included in the power data cable as well as the 2000 socket?
 
Ok here's the skinny;

The ais data over 34800 does not need the DSC set to receive any data from the gps for your chart plotter to show AIS targets. The plotter does all of the computational heavy lifting.

The mtech 550 , unlike the std horizon units is happy if you splice the gps tx high speed to it as well.

Make sure you configure the port on your plotter to nmea high speed and off you go.
 
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