NMEA baud rate converter 38400 to 4800

[gerry99]

Can anyone recommend a multiplexer or similar that will accept a NMEA 0183 input at 38400 baud (and ideally at least one other at 4800 baud) and output to 4800 baud with sufficient power to feed three devices?

Thanks

 

[PaulRainbow]

Check the spec of Shipmodul multplexors. Although, if you are planning to change AIS to 4800 you'll most likely get problems, especially in busy areas.

 

[macd]

...if you are planning to change AIS to 4800 you'll most likely get problems, especially in busy areas.

We often run AIS on 4800 (from a 'Radio Ocean' VHF which will output in either 4800 or 38400: the chartplotter is single port and also chats with something else at 4800). As you suggest, the display seems to be degraded somewhat, but not to a critical degree in the lowish traffic areas in which we generally sail. It may very well be more problematic in busy areas. (Although I'd have thought it should be fine in Berkshire )

 

[gerry99]

Thanks for the recommendation and feedback Paul,

I have a Vesper Marine WiFi AIS and am using the WiFi option for AIS itself. I was hoping to use the GPS data from the AIS unit to feed position information onto the NMEA 0183 bus which connects to my DSC radio, my ST60 instruments and the data repeater screen on my ICS Navtex, so all I really need is position data, although support for other sentences is useful. My two options are 1) NMEA multiplexer and 2) a second GPS unit like an Evermore SA320 which would output position data straight onto the NMEA bus at 4800 baud. The issue with the second option is the hassle of running another antenna cable through a tortuous wireway route to connect it to where I need it to be

 

[bitbaltic]

My shipmodul minipex-lite (which is USB powered and intended for use with a PC) will transform the 38400 0183 AIS data into 4800 on its single 0183 output port. It seems to do this okay (have checked the data stream with another PC) but I sail in relatively sparsely-populated areas and I wouldn't think it a great solution to push AIS into 4800 baud in busy areas, whatever hardware solution might turn up. Personally I would try some sort of 0183 GPS solution mounted inside close beneath the coachroof to avoid the cable run problem. Will the evermore work inside the boat?

This sort of thing might/should work fine inside a GRP boat: http://www.ebay.co.uk/itm/12-VOLT-R...442557?hash=item33c9e3343d:g:Uf0AAOSwxYxUz6si

 

[laika]

I wouldn't think it a great solution to push AIS into 4800 baud in busy areas, whatever hardware solution might turn up.

It's a fair point if you don't have the option of filtering out sentences you don't want but if the OP does invest in a higher end multiplexer, some of them at least offer the option of filtering/routing sentences. A look at the manuals suggests your miniplex lite doesn't do that but the miniplex 3 does. Essentially you'd feed in your AIS but set up the multiplexer to only send the required sentences down the 4800 baud link. Sounds like a considerably more expensive option than the Evermore (or a cheapo bu-355) but depends what other uses there may be for it on board

 

[bitbaltic]

It's a fair point if you don't have the option of filtering out sentences you don't want but if the OP does invest in a higher end multiplexer, some of them at least offer the option of filtering/routing sentences. A look at the manuals suggests your miniplex lite doesn't do that but the miniplex 3 does. Essentially you'd feed in your AIS but set up the multiplexer to only send the required sentences down the 4800 baud link. Sounds like a considerably more expensive option than the Evermore (or a cheapo bu-355) but depends what other uses there may be for it on board

Yes, I am aware that would be a solution. The reason I did not suggest it is because a) I know the miniplex lite does not do it and b) I would not suggest solving the OPs problem with a £350 multiplexer when a GPS box around 10% of that price would do. As you say if there were other uses for an expensive multiplexer on board then that might be a road to go down but the OP hasn't suggested that is the case.

 

[lpdsn]

I reckon you'd definitely have to filter out the VDM sentences to stop them getting to the 4.8Kb output (they're sent over 38.4Kb for a reason). ShipModul Miniplexer is a great bit of kit and can do what is wanted plus a lot more. Maybe a bit overkill for a simple requirement though, but I can't think of anything else cheaper (except maybe a YAPP project if he hadn't been driven away).

 

[PaulRainbow]

The multiplexer route is certainly one solution, provided the AIS is filtered out, but as already said it's an expensive solution if there is no real need for the other functionality.

A GPS, such as the Evermore should have no problems working inside the boat. My Garmin GPS is fitted under the deck above one of the aft cabin wardrobes. While i was setting my electronics up i had the GPS in the battery compartment under a saloon sofa for a couple of days, worked fine.

 

[lpdsn]

A GPS, such as the Evermore should have no problems working inside the boat. My Garmin GPS is fitted under the deck above one of the aft cabin wardrobes. While i was setting my electronics up i had the GPS in the battery compartment under a saloon sofa for a couple of days, worked fine.

I went sailing mid-project when replacing my GPS with a Garmin 158i. The reception with the internal aerial was very poor. As I'd already bought an external antenna I temporarily placed that on a shelf above the chart table. It was OK but not perfect (and sometimes fell over when beating ). I didn't get reliable reception until I'd mounted the entenna on the pushpit as per the original installation.

 

[PaulRainbow]

I went sailing mid-project when replacing my GPS with a Garmin 158i. The reception with the internal aerial was very poor. As I'd already bought an external antenna I temporarily placed that on a shelf above the chart table. It was OK but not perfect (and sometimes fell over when beating ). I didn't get reliable reception until I'd mounted the entenna on the pushpit as per the original installation.

Do you have lead decks

Not doubting your experience, but ;

My Garmin GPS is mounted using the Garmin umder deck mount : https://buy.garmin.com/en-US/US/p/13378

I also have one of those USB pucks as a backup, tucked under the roof lining beneath the side deck. They both work fine, as do the GPS receivers in my phone and tablet.

 

[lpdsn]

Do you have lead decks

Not sure what the explanation is. I usually carry the dinghy on the coachroof directly over the chart table, but can't think of a rational reason why that would make a difference.

 

[Vladis]

Can anyone recommend a multiplexer or similar that will accept a NMEA 0183 input at 38400 baud (and ideally at least one other at 4800 baud) and output to 4800 baud with sufficient power to feed three devices?

Thanks

Hello,

This multiplexer is able to translate 38.400 to 4.800. The power of its output is that of a Maxim 485 IC. The number of inputs that it is capable of driving depends on the input impedance of those inputs.

http://m.ebay.co.uk/itm/272680717148

Regards, Luis

 

[RichardS]

Hello,

This multiplexer is able to translate 38.400 to 4.800. The power of its output is that of a Maxim 485 IC. The number of inputs that it is capable of driving depends on the input impedance of those inputs.

http://m.ebay.co.uk/itm/272680717148

Regards, Luis

That appear to be a very interesting and useful device Luis at a good price.

I assume that you are the developer/seller.

Richard