Chris speculated that some of the weak carriers that we hear around 43 meters might be South American pirates and I tend to agree. Chances are good that some of the carriers are also North American pirates testing homebrew equipment, too. For that matter, I've seen some people test low-power equipment into an inadequate antenna (such as a wire across the floor), not expecting it to get out anywhere, but I wouldn't surprised if a few people could hear the weak carrier from it.
Enough speculating about the sources of weak carriers on 43m and back to the topic at hand: South American pirate radio . . . RCW, in particular.
Their Twitter feed is here (English translation)
Here's a brief log on YouTube with classical music
And here's a longer recording (but with weaker reception) on 6925 kHz from Brazil