Blue Sunray
Well-Known Member
You really, really, don't have a scooby about this.
AIS net marker buoys
- Thread starter pcatterall
- Start date
You really, really, don't have a scooby about this.
lw395
Well-Known Member
rszemeti
Well-Known Member
Generally speaking, they are used to help fishermen avoid lost tackle, either through getting run down by ships or by drifting off station in storms.
They only need to be short range devices, boats only need to be aware of them from a mile out at most.
Somewhere around 100mW, to a stubby antenna should make it out a mile, just about. They will be kinda weak and get clobbered by every other signal out there, but as they are stationary you only need one good "read" to get a fix on them.
They only need to be short range devices, boats only need to be aware of them from a mile out at most.
Somewhere around 100mW, to a stubby antenna should make it out a mile, just about. They will be kinda weak and get clobbered by every other signal out there, but as they are stationary you only need one good "read" to get a fix on them.
lw395
Well-Known Member
The Matsutec offering has a claimed 10 mile range and 2-3W power. More powerful models exist.
https://www.advancednetting.co.uk/dhan-buoy-equipment-c-76_149/ais-buoymarker-p-1418.html
dgadee
Well-Known Member
ShinyShoe said:Pot markers presumably on one end of a string of pots - how many strings in a 1mile radius though?
Can someone point me to where there are a load of these in a 1mile area... I figure they have a second hand value
I remember forests of flagged pots as I was going up the east coast of England.
rszemeti
Well-Known Member
That looks good value! I wonder if it could be persuaded to work off 12V as a fixed install on a boat ...
Plum
Well-Known Member
Even if you did that, it is a transmit only device. You would, I assume, have an AIS receiver already but how would you stop your receiver constantly receiving your own transmitted signal from the net marker device creating a target always in the centre of your screen?
Www.solocoastalsailing.co.uk
ShinyShoe
Well-Known Member
The receiver would send data to plotter. Plotter would know the MMSI and filter it?
ShinyShoe
Well-Known Member
But, I've just given this more thought.
The transmitted data is only position. no course / sog.
That means other vessels can't plan a CPA. Or worse still, may plan to pass you thinking you are stationary.
I'm sure charging can be solved (on a li ion battery). The unit it intended to be 1m+ above water line. Charging in position may be harder...
The transmitted data is only position. no course / sog.
That means other vessels can't plan a CPA. Or worse still, may plan to pass you thinking you are stationary.
I'm sure charging can be solved (on a li ion battery). The unit it intended to be 1m+ above water line. Charging in position may be harder...
rszemeti
Well-Known Member
I would very much doubt it is only position ... even the cheapest, most basic GPS chip outputs speed/heading sentences .. I find it hard to believe they would not transmit that data, as they have it, and it is part of the AIS packet by default.
TSB240
Well-Known Member
Just to add some more confusion some of the newer Class B transponders are now also SOTDMA like class A
lw395
Well-Known Member
You're probably right.
But I don't understand the enthusiasm for an illegal device which transmits its position to the authorities every 3 minutes.
LittleSister
Well-Known Member
The forests of flagged pots are less of a problem than the dense undergrowth of unflagged ones!
ShinyShoe
Well-Known Member
Assuming you can reprogram the MMSI - the one provided you can - how would the "authorities" spot the device was illegal?
And if they did - and actually took some action - what action would you expect? I'd expect confiscation and told not to do it again while you say 'so sorry - didn't know it was "illegal" coz the manufacturer listed a load of standard and I didn't know to look for CE'
david_bagshaw
Well-Known Member
american ais kit has to be programmed by selling dealer, owners are not allowed to put in the mmsi.
rogerthebodger
Well-Known Member
That is true for EPIRB's but I programed my MMSI in my DSC radio myself and you may program the MMSI number into an AIS transponder. I purchased my DSC radio directly from the US and was collected personally from the US
A net marker is a simple form of AIS transponder well transmitter actually.
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ShinyShoe
Well-Known Member
And certainly the one posted comes with software to program
david_bagshaw
Well-Known Member
Interesting, I stand corrected, i was only going on the instructions of a digital yacht ais, which clearly states it is against american law for the owner to program the device.
ears media
Member
I've sold loads of these things and it's quite rare to find any appearing on Shipfinder/vesselfinder etc because they're just low powered and low in the water as has been mentioned. Conversely, a few people cable tie them to the mast of a boat where they want other people to know it is there. The burst repetition I tend to set is 5 minutes for crab pots (quite a common one), and the vessel name field has crab pot 1 to crab pot 2 - that kind of ID. OFCOM wise, most people apply for ships portable licences which don't require a vessel name and generate an MMSI, and they just do more than one if they need multiple MMSIs. Not ideal, but OFCOM have a name and address in case of issues and as far as I'm aware, don't seem concerned. In real terms, they are just low power, short range devices that have very short duty cycle. They are fully identified, and therefore controllable if necessary. The current licence situation is detailed for all automated devices apart from those within the VHF marine band - so presumably, OFCOM are not seeking additional regulatory powers. In fact, they are simplifying most bands now - with many previously controlled devices now being permitted - parachutes, microlights and airborne comm devices are being made simpler to control and operate.
The net markers can be programmed in a variety of ways - extended mode allows the vessel type and sizes to be entered, and net markers tend to be designated 'fishing', while those cable tied to masts to give AIS presence just get yacht or leisure craft applied. The entered times between bursts also seem slightly variable. Setting 3 minutes might be 2:57, or 3:05 - enabling less clashes if set to the same setting. I personally make small changes to the time settings depending on where they will go. Somebody protecting their equipment in constantly changing locations might identify more regularly, while a once a week crab pot could easily reduce to 10 mins without loss of effectiveness in areas with less traffic and slower speeds.
The one thing that happens, despite warnings is that people will try to reuse an MMSI. They use their boat MMSI and I get a call telling me their boat is suddenly called crab pot 1, because the crab pot transmitter got into the network and the boat name gets replaced. It often takes quite a while for the boat name to repopulate the system and change the name back to the correct one. Telling people info on radios really does not sink in. People who get annoyed a radio asks for an MMSI every power up, so they enter 123456789 to silence the alarm, then they eventually get an MMSI and get cross they have to return the radio for me to reprogram. Some do have reset modes hidden - and some are very well hidden, but others do need the software. Radios in my neck of the wood are very annoying - people come over from Holland and leave their end of transmission data burst on. It's not used here, and the buzz is very annoying.
The net markers can be programmed in a variety of ways - extended mode allows the vessel type and sizes to be entered, and net markers tend to be designated 'fishing', while those cable tied to masts to give AIS presence just get yacht or leisure craft applied. The entered times between bursts also seem slightly variable. Setting 3 minutes might be 2:57, or 3:05 - enabling less clashes if set to the same setting. I personally make small changes to the time settings depending on where they will go. Somebody protecting their equipment in constantly changing locations might identify more regularly, while a once a week crab pot could easily reduce to 10 mins without loss of effectiveness in areas with less traffic and slower speeds.
The one thing that happens, despite warnings is that people will try to reuse an MMSI. They use their boat MMSI and I get a call telling me their boat is suddenly called crab pot 1, because the crab pot transmitter got into the network and the boat name gets replaced. It often takes quite a while for the boat name to repopulate the system and change the name back to the correct one. Telling people info on radios really does not sink in. People who get annoyed a radio asks for an MMSI every power up, so they enter 123456789 to silence the alarm, then they eventually get an MMSI and get cross they have to return the radio for me to reprogram. Some do have reset modes hidden - and some are very well hidden, but others do need the software. Radios in my neck of the wood are very annoying - people come over from Holland and leave their end of transmission data burst on. It's not used here, and the buzz is very annoying.