When worlds collide:
I bought an AIS (Automatic Identification System) transponder for my sailboat. If you don't know what these are, they are a doohickey that transmits your boat GPS position, speed and direction (among other bits of data like name and boat size and stuff). It's how sites like marinetraffic.com get populated with live ship position feeds. It also lets you set up computers on your boat to warn you if you are on a collision course with another boat that has AIS. For example. Very helpful during fog, at night, or when people do people things like fall asleep.
Anyway transponders are interesting. When you buy them, you have to provide the seller with your boat's MMSI (Maritime Mobile Service Identity). The seller then configures the radio with the MMSI before giving you the radio.
If you want to change the MMSI later, say because you bought a new boat and want to move your thousand dollar radio to it, you have to beg and plead (and probably pay) to get a special unlock code from the manufacturer. Sometimes you actually have to mail the radio back to the manufacturer to get it reset with the new MMSI. I did a little sleuthing and RE and figured out that the unlock code for my radio is derived using a pretty simple algorithm. So when it comes time to get a new boat, I can Do It Myself thankfully.
Perhaps not surprisingly, DOT and FCC get really cranky about people talking about AIS transponder resets in too much detail. They don't want such knowledge to become well known or understood for fear of people changing their own transponder MMSI to someone else's I guess? It's odd though, considering the protocol is plaintext and you can implement it easily with a cheap SDR (see for example:
https://jeremyclark.ca/wp/nav/rtl-sdr-for-ais/ ) . The protections against transponder resets seem like security theater.
Anywho, will be interesting to play with AIS on the Big Lake in the coming weeks. It really was neat to crew on a friend's boat during a big race (~19 boats), as most of the race boats out of Duluth have transponders. And thankfully I could pull the trigger on this even though I know my boat is not my forever-boat. It's nice to know that this quite expensive radio will be usable in the new boat, whatever it might be.