Only vessels under International SOLAS regulation are required to broadcast Class A AIS signals. If you are under SOLAS regulation you may not turn off your signal. AIS is not required in Inland waters except under national regulations
For Class B AIS you may want to review the following:
Nautical Institute AIS Forum: Technical Feedback
This talks about the ineffectiveness of using Class B Transponders for avoiding collisions. It essentially places these units in doubt based on a collision
this past June with a Bulk Carrier and a yacht. Both vessels were not providing a proper lookout and the bulk carrier failed to render assistance. The yacht skipper
was dismasted and he was able to recover the mast
and cut away the head
sail and motor
back to port.
Since your yacht is not required to broadcast AIS signals the use of them in not mandatory. There is regulations
stating that if you install and AIS transponder you are required to use it. Should you have a collision
and are not broadcasting it could be considered a violation.
Having an AIS receiver is of substantial value but the use of transponders to warn other vessels of your location is not so clear cut. Your obligation to maintain watch and augmented radar
visibility is not reduced by broadcasting AIS. While it might aid in your visibility is is not a means to place the obligation totally on the other vessel.
If you have security
concerns about divulging your position the range of AIS is no greater than VHF
signal propagation. If you are in areas where you might require a higher attention to security
you would normally be farther off shore than VHF transmission
range any way.
Also note Military ships are NOT required to broadcast AIS and I would think in areas where you might want yours off they would certainly have theirs off.
AIS has it's positive uses but it really does not change the game
very much for a small boat. You still have to do all the things you would as if you had no AIS. The times when you might be concerned for your own security would also correlate to the areas where having a signal to identify yourself would also avoid a collision.
Having a receiver I feel is a good idea and a valuable tool, but broadcasting when you are not required to do so has a lower value since based on the one incident a large ship didn't see the small yacht, failed to detect the AIS broadcast, collided with the yacht and went on with the trip as if nothing happened. For that reason, you are better served to be more defensive in maintaining watch using a receiver but not as a well served as a broadcaster. The big ships just don't care about you and would choose to ignore you as much as possible. It is illegal for them to do so but you have obligations as well. That fact seems to weigh heavier than the notion of piracy
on the high seas. The number of confirmed piracy
actions on the high seas with yachts is minuscule. Collisions with large ships is far greater. Playing the low percentage rather than the big percentage that carries a high death rate just isn't good bet.
It is a game
of percentages. The only high percentage for you is the most active defense. Hiding would be a lower percentage success rate.