I couldn't hear Radio Nacional Amazonia at all here on 11780 yesterday evening, while they came in OK on 6180. Usually they come in much stronger on 11780 than on 6180.
As for 31m, it's usually sparsely populated at my location, except for the Voice of Greece, CRI and some religious broadcasts from the U.S. Too bad VoG doesn't have an English language service, even though they do target North America at night. During their hourly ID a female announcer says in perfect English, "You are listening to the Voice of Greece." However, the rest of the broadcast is Greek to me.