The USCG doesn't know squat about the RoR. They're an administrative organization and they happen to publish the damn book.
I'm going to bow out on this discussion. There's been speculation enough. The proper signal to use is any of those approved as signals to attract attention. Correct, there is no specific signal assigned to a vessel at
anchor in good visibility. So, see signals to attract attention. Ignorance of ho 102 is not an excuse nor is the ignorance of education.
And before everyone on the other side of this gets over-heated let me say that I went through this. I SOUNDED THE DANGER SIGNAL REPEATEDLY. The court did not hold our vessel, myself, the third mate or her master at fault. They assigned us zero liability. But they also said that the danger signal was not the appropriate signal, the rules only allowed for it to be used by vessels underway, and that the master of the SL-7 was only given probation on his license due to the reasonable doubt in his mind by our use of that signal. The guy hit us on an almost full moon night with unlimited visibility, our deck lit up like a carnival, and he got not even a slap on the wrist. The court expressed that 'Uniform' would have been the whistle signal probably appropriate. I took the opportunity to check with the three instructors who teach the various courses in RoR at the US Merchant Marine Academy and all three confirmed that the danger signal is only for vessels underway. Obviously, it was news to me!
You guys can believe whatever you damn well please. I spent the better part of a day in lovely Philadelphia in a proceeding that is designed to make your hair hurt, in a professional sense. By the time you're done with one of those you wonder what you possibly did that was correct! I got the message from them loud and clear and while I may not know if my dog loves me, my wife is faithful to me, or that the sun rises in the east-I do know that you do not use the danger signal while at
anchor. (g)