This site is dedicated to AIS. AIS or Automated Identification System of shipping and has been compulsory for shipping since 2004. All ships over 300 Tonnes are required by International law to transmit an AIS signal every few seconds when under way. This signal can be heard on your marine VHF Ch. 87 (161.975) or 88 (162.025) Int. as a very short burst of sound. In that burst of sound, the ships position, course, speed, name and maybe other data as well is transmitted. Passenger carriers and many private vessels also transmit, usually as a class B vessel, and are not required to give as much information. WARNING> Do NOT rely too much on AIS if operating in the Pacific, where Chineese registry fishing ships operate, some actually transmit but I think the cost of a class a transponder is to much for the ship owners.(Paint certainly is).Their seamanship is also suspect. But at least they are usually only in sight of land - So sue me!
The VHF signal cannot be decoded without some simple modifications being made to the set, although it can be heard.
The information here is for sailor’s safety, and not intended for home monitoring, although there is an overlap.
From a practical aspect of sailing long distances and watch keeping with a reduced crew. Every reliable assistance must be considered.
As most short-handed yachtsmen are sailing on a limited budget (as I am), I am including a few addresses to sites that allow you to monitor shipping at sea.
Some years ago while researching AIS and various systems I came across a web site selling an AIS plotting program, He also had a schematic for an alarm for AIS. Unfortunately he has withdrawn his program and schematic from the market.
The idea of an ais alarm connected to your existing VHF with no modifications, really fired my interest. I made his alarm and could sometimes get it to work. Not good enough, so had an electronics wiz design an alarm for me. It is so reliable and simple to use, I have been asked to make them for a number of sailors. There are now two models being made, the main one has a 90dB buzzer, quite loud enough for normal work, the other has a 100 or 105dB duel alarm.(About the same as a house-hold smoke alarm.) I used one of these on a 1500-mile voyage last winter and found it a bit too loud for me except while under motor. There is one main disadvantage to the unit: if using a masthead aerial then the alarm is activated whilst the ship is still over the horizon. Possibly never to be seen. (This depends upon atmospherics at the time.) As this is a sound activated device, - sound= energy, and hence an electrical current, then it follows that the same unit can be adapted for other uses, for example, I drive a burglar alarm on my boat with one, use an LPG sensor hooked up to one and you have a much cheeper, and if you make it yourself perhaps more reliable unit. The list goes on. It requires about one half volt to activate. (max 30 volts) but uses milliamps.
I am a believer in the idea and feel it will save lives- maybe even my one. Hence I am now making them commercially. If you feel that $95 NZ is too much but like the idea E-mail me and I will send you a schematic of my design so you can make your own, or better still manufacture them and under sell mine. To the best of my knowledge there is nobody else making an AIS Alarm worldwide.
DIY To take this a step further then a warning alarm and if you have a computer on board it is relatively easy to download (mostly for free) programs to monitor ships. Firstly you will need to modify your radio,ie: fit a discriminator, better still buy a cheep VHF scanner and use its own little aerial down at deck level- that still gives it about a 10 mile range. Also available are dedicated AIS digital receivers, which work very well for decoding
If you want to use a VHF radio to track nearby shipping than it is necessary to convert your analog VHF signal to digital at some point, as well as removing some of the filtering of signal from the radio. It sounds sort of technical but is all quite simple. First the radio must be modified, to decode the signal. Most VHF's can be modified, Most of them you can do yourself, otherwise a radio tech. with an oscilloscope will do it for you. The modification will not impair the other uses of a radio, a separate output is fitted. (Go to discriminator.nl, for a list of radios and how-to)
Next step is to download AISMon and a VSPE (Virtual Serial Port Emulator), sites below.
A stereo or mono cable from the radio to your computer and you are in business.
Note each time you start your monitoring, and if you use the VSPE listed here then go to "device", "create" "pair" and follow your COM port requirements.
VHF gives quite adequate results for plotting but a dedicated digital receiver is best. Around $200 and upwards. Or a class 2 transponder can be purchased for about $500 US and upwards
Personally I use an ais alarm from my cheap VHF scanner/receiver; once the ais alarm sounds then turn on my computer, start VSPC, AISMon and Open CPN running cm93 charts. A bit long winded, but it works. I don’t like to know about ships passing 30 to 50 miles away so I have an aerial a little above deck level on my scanner, that gives a range little more than the horizon. Otherwise I would recommend a seperate dedicated aerial; I was using a "Slim Jim" aerial, a unit to make yourself using TV ribbon in a plastic tube. Works well, and plans available for free on the net.-Also cheep to make. But it receives a signal laterally only, no good if under sail as I found out earlier this year, good signal 10 miles away but nothing under 2 miles.
http://www.coaa.co.uk/shipplotter.htm "Ship plotter" one of the most popular programmes. Well worth playing with. But it costs 25 Euros after 21 days free trial. Also has info on some VHF radios and adaptation
http://www.discriminator.nl/index-en.html . This site is a must if you want to decode signals using standard VHF and a computer. FREE
http://groups.yahoo.com/group/aismon/ It is necessary to sign up with Yahoo groups to download and use AIS Mon. (FREE) AIS Mon decodes the signal for you, and will send it to your charting program.
http://opencpn.org/drupal/ Here is a FREE charting program. It may not be quite as good as some of the other expensive ones but it reads a variety of chart formats, shows your position, and any targets (ships) on the screen. You will need to acquire your charts elsewhere.
http://www.sping.com/seaclear/ I have not used this program so cannot comment on its use. It uses Raster charts and has that magic word- FREE.
http://www.stentec.com/en/navigation/wingps-5-series WinGPS5 software again I haven’t used it but again FREE.
http://www.eterlogic.com/Products.VSPE.html If using a VHF,decoder such as AISMon there a serial port emulator is required. It is a bit of a nuisance but necessary, to open VSPE (virtual serial port emulator), AISMom then a charting program. Note: this VSPE is free to 32 bit users i.e. up to and including Windows XP but to use on Windows 7 a pay for version is necessary. Windows7 is 64 bit and software writers must pay an annual license fee to use. Therefore a "not new" computer is best for your Yacht.
http://en.wikipedia.org/wiki/Automatic_Identification_System No systems but worth reading for general knowledge. Also has links to a number of sites and references.
AIS web sites- Commercial
http://www.thegpsstore.com/Icom-MXA-5000-AIS-Receiver-P2014.aspx This site has a dedicated AIS receiver at $350
http://www.thegpsstore.com/AIS-Equipment-C388.aspx Or fit your own class B transponder (before all yachts are required to do so) $830
http://www.crystal.co.nz/products_ais_equipment.html Vesper marine, support NZ made. Their web site doesn’t give prices and not too much about their products. Have to E-mail them. But I know they make and sell a dedicated AIS receiver with its own plotting screen and built in alarm(which cannot be heard by anyone without perfect hearing and within 10 feet). But they told me an external alarm can be fitted.
http://www.myboatsgear.com/newsletter/AIS.asp Here is a site with AIS digital receivers for around $200. I have used one of their models shown and found it very good. More sensitive then my old Icon scanner/receiver. But it is dedicated to AIS so cannot be used as a VHF receiver ie.weather reports or faxes.
http://tcb.en.alibaba.com/productshowimg/508784320-210109371/Marine_AIS_Class_B_Transponder_M4501.html?tracelog=cgsotherproduct1 Another site selling class B transponders. Don’t know anything about them or their pricing.But their site title is sure long.
http://www.yachtinsure.com/news-auto-identification-systems.htm More info on AIS.
http://www.ehow.com/how_2021665_boat-receive-ais.html May be helpful.