VHF splitters for AIS or separate aerial ?

[gavina]

I have used an Easysplit OCB splitter with a Comar CSB200 and found that we could see ships 25 miles from Haslar. There have been no apparent effects on the VHF radio and I did not have to fit another antenna on the pushpit. I have to declare an interest as we sell AIS through Sea Whisper and have sold units for fitting either way with no complaints from anyone.

 

[gavina]

ICOM have added an optional AIS receiver to the M505 and M603 models. As they scan all channels including AIS the rate of data update is slower than for standalone AIS kit. The PCPlotter navigation programme can be configured for use with these models so that target loss between scans is minimised. A great advantage is that no splitter is required.

 

[ditchcrawler]

Navicom make a combined VHF DSC/AIS radio .The model is Navicom RT650 available for just over £300.

 

[alan]

Thanks for that info. Of course with a fast processor and DSP it should be very fast
but maybe they have not gone full DSP and really are scanning analogically as you say.
Out of interest, do they have a separate NMEA output port for the AIS data or do they just display it in text format on the radio??

Alan.

 

[gavina]

There is a separate output so that the data can be displayed through a suitably configured chart plotter or PC.

 

[gavina]

Concerning the reliability of splitter arrangments I understand that the EasySplit OCB splitter is designed to fail safe in the event of power loss to the unit to give an unimpeded path between the marine radio and its antenna. Apparently this was a requirement of German government standards.

 

[chriscallender]

Hi

I've recently been (not very actively) looking into this. For example, looking at Shipplotter software search for it on google, and sites like http://www.discriminator.nl/ais/index-en.html

So the good news is that AIS signal can be decoded even by a laptop soundcard, no need for fancy DSP. The downsides are

- You'd need to buy a second VHF receiver (or two if you want to simulatenously monitor both AIS frequency, although maybe dual watch would help with that, but always with the risk of missing messages). OK you could tripple watch with ch16 as wel. I guess that needing a dedicated receiver or 2 is what is putting off the add on to a marine VHF radio.

- You need a discriminator output from the radio, which would normally be a soldering iron mod, invalidated warrenties etc.

However, I've got this old VHF scanner (receive only) which I might have a play at using as a poor man's AIS with these kidn of mods, assumung there is ever a day when I'm not working.