Today’s story on flight MH370 is that pings got picked up by a Chinese ships. Blackboxes seem to emit a signal every second for a couple of weeks.
Maybe it would be better if these devices would send a ping not every even second. Technically it should be easy to give black boxes a fix random
ping frequency. I probably would help that the device you are looking for emits a ping every 1.345 seconds.
And bigger batteries are probably a good idea as well.