NASA AIS Engine - not sensitive enough?

[fireball]

Quick trip across to Bembridge on Friday and we had 3 cruiseships displayed on the CP using the NASA AIS engine ... I've always been disappointed in the performance of our engine - it doesn't seem to pick anything up until it is too late ....

So ... just to test my antenna installation (which seems fine on VHF, but that doesn't really "test" it ..) I borrowed a NASA AIS Display - this is the all in one unit that doesn't output to a CP ... as I didn't have a GPS input to it I just listed the targets it was acquiring ... and they rattled down the page at about 2 each second - quite reasonable I thought - well, proves that at low water in Bembridge my antenna on the pushpit should be adequate ....
Then ... plugged in my engine and looked at the "output" on the CP data display (this just shows the raw data coming into the port - I know from previous tests that this is the same to a PC using the supplied serial cable - so is accurate) ... and I could boil the kettle inbetween target signals .... so why oh why oh why is my Nasa AIS engine so crap?

I thought it might be a "sensitivity" setting - but having looked up some other websites with how to programatically change the engine it seems it resets back to manufacturers settings on powerdown - so can't be that ....

I'm about to take a screwdriver to it (just opening the case!!) .... but I'm not sure that will show anything helpful....

 

[shmoo]

What you describe doesn't fit with my experience of the engine. Couple of test cases:

1) In Woodbridge, 8 miles up the Deben from the sea: on pushpit antenna, nothing; on main VHF antenna at masthead, all of ships in Felixtowe and Harwich Haven, dozens of ships

2) In Levington about 2 or 3 miles up the Orwell, pushpit antenna: all of Felixtowe and Harwich Haven, dozens of ships. Ships as far out as Sunk.

Usually at sea we expect to pick up vessels before they come into view in good vis. In busy areas like Dover or Off Casquets we expect, and see, dozens of vessels.

When we look at the raw NMEA coming from the engine there are several messages a second.

The only vessels of any size we have been surprised by (ie didn't see on AIS) have been warships off the south coast.

 

[Talbot]

Never had any trouble with mine. However, do you use the the GPS input through the engine or direct to the laptop, as the AIS throughput is normally at a much higher rate than used by the GPS, and I think, adding the GPS signal may also slow the engine down to the same throughput (suspicion, not proven)

Personally, I put the GPS signal directly into the laptop and then share it to whatever programme requires it, using Franson.

 

[fireball]

The Engine isn't a fixed unit - there are quite a number of components on the board that have adjustments ... I'd guess that at least one of these is a squelch ... what I can only assume is that our engine is not set up correctly ....

The reason I tested against another known good unit was that I then knew whether it was the antenna or the engine - as the known good display was giving plenty of targets up to around 10 miles away (whilst we were tucked up deep inside bembridge harbour at low tide) and the engine gave 3 all within 4 miles I can conclude that in my case the engine is at fault.

 

[fireball]

Kept it simple - exclude all external influences - no GPS throughput - don't need it with the CP180i anyway as it has it's own gps ...

Just disappointed with the performance of my engine - I had hoped that it would be good - hence I suspected the antenna installation - however - as I said - I proved that good ....

 

[Talbot]

so it is one of three things:

defective AIS engine
a problem in the plotter
a defect in the wiring between them.

I used serial to USB leads from Easysync that have leds on the plugs, which enables me to see that data is being transferred. But you can also see the resultant data in the laptop anyway by using the appropriate software.

 

[fireball]

Well - I can discount the problem with the plotter or the defective wiring as I get the same number of targets using a standard PC with a serial port using the supplied cable, not only that, but the rate that the transmissions come through is the same - using Hyperterminal - so although I can't identify the targets I know there isn't a lot of traffic coming through ... so I'm left with the engine ....

As the engine is providing an output it just isn't outputing all the traffic that I know to be available (by comparing with an AIS display from the same company) - therefore I can only assume that either the radio is "squelched out" ... or it is disregarding those transmissions for some reason.

I did think about the possibility of programing it - telling it what sensitivity to use etc - but as this resets when it looses power it would not be a fix and I can't see that it will make any difference - it resets to maximum sensitivity and switches between the chanels ... I suppose the next step could be to make a more detailed examination of a known working engine and mine - compare where the dials are turned too .... it could be just a false adjustment ... I doubt it is a component failure, although there could be a corrupt programme in the chip ??

 

[HenryB]

My own NASA AIS engine gives excellent results, frequently showing vessels 60 miles away. Is there any chance that your CP isn't set up with the correct serial port settings?

From memory they should be 38400 baud, 8 bits, no parity, 1 stop bit and no handshaking.

 

[Alfie168]

At the risk of stating the obvious, why not ring NASA and have a word with them. Everyone says they are very helpful. I'm sure they would check it out for you as it seems on the face of it there is a fault with the unit if you are getting good results on another. Its better than breaking it for definite by twiddling inside it I'd have thought.

Tim

 

[Talbot]

agree that the NASA engine does appear to be the culprit, and that the best diagnostic would be a substitute. Sorry I cant help you there.

I have found NASA to be very helpfull when I had a problem. I sent my engine off for testing, and it was returned very quickly.

 

[fireball]

Thanks - I have emailed them .... but as it is a bank holiday not expecting a swift response ...

Despite knowledge of circuit boards, my knowledge is not detailed enough to reverse engineer the design and fix it without outside help .. /forums/images/graemlins/frown.gif

 

[fireball]

I'm in IT and regularly fix everything from stuck toners to web scripts and servers ... I'm used to diagnostics and am happy that it is the engine at fault ....

 

[fireball]

NASA have just replied:

[ QUOTE ]
There are no manual squelch controls and it should be comparable in sensitivity to the AIS Radar. Suggest you return to us for test, we will take into account the age but our repair charges are modest anyhow.


NASA Marine

[/ QUOTE ]

Not bad for a Bank holiday weekend ....

 

[mldpt]

I am having the same thoughts, I had the stand alone Nasa AIS, which worked fine picked boats up way off, but I wanted to link it to my Raymarine C120 so bought the engine, and I am very dissapointed with the results although it does show everything within about 7 nm on screen but I feel it should do better than that. I have my GPS routed through the Ais engine as there is only one NMEA input and this has to be set for 34,000 Baud rate so the Gps connects to the blue wire into the AIS and works OK, I did notice yesterday that there is a setting on the plotter which reads something like show all AIS targets or show only dangerous targets, but in the marina its hard to be sure, I look forward to hearing your outcome. I have spoken with Nasa they seemed to think it would be my ariel but I have two mast head VHF ariels both work my radio OK.
Regards Mike

 

[fireball]

If you still have the standalone one then connect it in place of your engine and see how many targets you get - you can just count the frequency of the reception .... then, if the C120 will show raw data input do the same with the engine - I suggest you turn off the GPS ... you should expect the same frequency of signals .. if not, then the engine is not working as well as the standalone unit.
7Nm is next to useless as you can see the blummin things by that point ...

 

[fireball]

Just as a quick update - came home today to a UPS InfoNotice through my door .... quick phone call to change delivery location and enquired as to who had sent it - NASA Marine ... hmm ... well - as it is a "packet" I can only assume it is an AIS engine - an invoice would've come through normal post ... so the question is - have they fixed it? have they replaced it? have they decided there is nothing wrong and just returned it? Are they charging me for anything?They haven't emailed or phoned me (nor I them - they've only had it a week - so was going to call them in the next few days). The only slightly annoying thing is that I did give my works address for return (enclosed in the letter with the unit) - but hey I'm not _that_ bothered.

So - tomorrow I will be one of
1) Happy bunny (they've fixed it)
2) Very happy bunny (they've replaced it)
3) Grumpy bunny (they're charging me more than I think it was worth)
4) Exceedingly grumpy bunny (they've decided there is nothing wrong with it)

we'll see!

 

[BlueSkyNick]

I missed this thread first time around, and have had a similar experience with poor reception, so I look forward to the next installment !

 

[fireball]

I'm between 1 and 2 ....

The report says they've replaced the "inductor" ... however I believe they've replaced the whole board (tell-tail signs see!)- the case is the same though.

There is a note of a CC charge required - £9.99 delivery via UPS .. So I guess there will be an invoice in the post - it's a little painful to have to pay delivery on something that was never right, but if this fixes it then for a tenner it will be worth it.

I'll try and test it this weekend - it should be fairly obvious ...


Nick - what range did you think you were getting? We'll have to arrange to meet up somewhere and swap kit about to test it.

S/n of my unit is V0517 - could be a batch of dodgy units about?

 

[BlueSkyNick]

I reckon I'm picking up ships at 7-10 miles, which always struck me as poor, especially as the likes of oldhand and tome, whose opinions I always respect(ed), have talked of 60miles on good days.

I had been assuming it was my crap cabling, until I read this thread!

will look forward to how well yours works from now on.

 

[fireball]

I'm now a very happy bunny - AIS plugged in and works fine ... swapped it over to the mast head antenna to get an idea for the range it will now receive ... whilst sat on our mooring in Chi Harbour

Was happy when I got Bembridge anchorage ... then scrolled across to get the yellow smoke machines at Ryde ... bit further and the IanGrant crushers going into Wooton Creek .... carried on across and there were a couple of ships just around Cowes .... up Southampton water - still receiving ...

Zoom out ... and go down south - a ship or 2 in the deep water anchorage ... and then 2 in the main English Channel ... 30Nm away ... thats better!!

Now I just need to see how it works on the pushpit - not so far maybe, but it'll be the antenna at fault - not the engine - thanks NASA Marine ...