Ten bucks more will get you a reliable, proven AIS receiver, the SR 161.

Nasa Marine makes great gear and reasonably priced too. Very popular here in the UK where they're based. I've got their AIS engine 2. That upgrade (from "1") meant they put a pair of LEDs indicating power and signal receipt. Real easy to install. Instructions run all of 2 pages. Couldn't tell from their website what the "3" upgrade means. No affiliation other than a happy customer of multiple products.

I'm not a fan of NASA AIS receivers as explained here:

http://www.panbo.com/archives/2008/03/nasa_ais_engine_2_as_screwy_as_1.html

Nasa did finally stop misrepresenting their AIS output as NMEA 2000 but I understand that lot of people have had trouble with their unnecessary filtering of AIS messages.

Also, everyone should realize that single receivers like NASA's and the SR 161 only receive half the AIS messages, even if they switch back and forth across the two frequencies. This doesn't matter too much with Class A, because they transmit often, but it means that Class B dynamic data will only be received once per minute, at best. The result is a jumpy target plot in close quarters.

The Nasa engine 3 is an upgrade from the engine 2 that gets rid of the messages restrictions and some other restrictions that where in the engine2 to allow the throughput of the GPS signal to the PC. This last utility however stays , also in the engine 3.
If you already have a engine 2 , Nasa can supply an much cheaper upgrade chip which will provide the same performance as the engine 3.

I recently upgraded my NASA ais engine 2 with a GBP12 chip and now used it for three weeks at sea.
The results are very good.
I connected the nasa to my arymarine plotter and am able to see ships up to 50 miles away or more!
I think with the upgrade chip its a very good piece of equipment.

Just get the new digital yacht when its out proper dual channel

Hi Penguin,
The upgrade for Nasa 3 was a new processor which now recieves all available messages . The Nasa 2 did not!.
I ordered this new chip at Nasa directly and got it for about GBP10. The results are very good.
I normally recieve all AIS targets within 25 NMiles radius and often moch more!
I connected the upgraded AIS2 to my Raymarine 50D plotter and it works fabuleously. In the raymarine there is a function that computes the possible collision point if you give the AIS target a vector.
That way you can directly see wether the vessel passes in front or behind you or if a collision is to be expected without course change! Its a feature that is not clearly in the Raymarine manual and work similar to MARPA at a radar system.

I am a BIG fan of Alan Mulley's NASA Gear, I have had about a dozen different items over ten years and nothing has ever let me down.
I got the upgrade chip from AIS Version 2 to 3 FOC, as I bought the V2 at the same time (unknowingly) that the V3 was announced. Can't complain about that.
OK so it's no frills gear, documentation not brilliant, BUT it always does what it says on the tin. Just a bit of DIY knowledge needed. By their own admission NASA target (no pun intended) the lower end of the yottie DIY market.The best piece of kit by far was the NASA HF3/P Comms RX which actually at times outperformed my Yeasu FT 847 and is around £900 cheaper. I also like the clipper range of instruments particularly the GPS repeater.

AS far as the AIS Mk3 goes, it now does all class A and B and Base stations. It switches every 30 secs, and Ive used it in the English Channel where an AIS is really needed and is not just a boaters toy, and beleive me the NASA doesn't miss much if anything at all. And of course the majority of NASA gear is actually made in the UK, not China or anywhere else.
It is also the biggest selling Leisure AIS in the world and is re-branded also under several other names.

Steve

Steve, Do you know why NASA built message filtering into their earlier receivers? It doesn't seem at all necessary, nor a cost saver, but it does seem to be the main reason users had to install new chips to receive Class B and other info. Why?

Hi,
The new nasa engine 3 and the upgraded engine 2 no longer have a message filtering! That filtering was used to limit the processor work. The upgrade and the nasa 3 have a better processor which doen't need this message filtering.
As far as I can see the nasa 3 and the sr161 will have the same performance . The SR162 which is a two channel reciever has better performance because it recieves at a higher frequency. This however is hardly a problem normally to my experience this summer ( two month cruise using nasa2+upgrade).

To be honest Ben I dont know for sure, but there must have been a reason, NASA is not a company noted for doing extra work for no resaon!
At a guess, and it is just a guess, I would think that it was probably either on the advice of the MCA (UKCG) or IMO.
Of course when NASA first released the original AIS black box and Screen version, they were pioneers in the Leisure market and there was no Class B to speak of, this is what...9 or 10 years ago?
I suspect that not allowing Base stations through the filter, or ships destinations and Cargo info was probably a security measure, as you guys know, they were bad times.
Class B is generally still frowned on here by the commercial shipping industry and some authorities at least in the English Channel and Southern North Sea, where it is generally regarded as unwanted clutter in the #1 busy place. Lets be honest, a 35000 DWT tanker has neither the ability nor the inclination to slow down or change course quickly to start avoiding class B vessels.
We're down at our holiday place on the south coast for a week, and then we're going over to Swansea to the boat for a few days. I'm probably wrong but when I get back I'll ask "Shux" the MCA Comms manager and see if he'll give me a definitive as to why...he'll know if anyone does. I doubt that NASA will be forthcoming.

Cheers for Now

Steve.