on our way back from ô môn, i saw many tv antennas like those. i asked why they were so big and they said that it was because this place was located next to the border with many different provinces so they were trying to get as many channels as possible by having big antennas. then i came back to ho chi minh-city and realized that they also had big antennas here... i thus have no real explanation for this...
moodoscope: http://www.youtube.com/watch?v=8XhB1yaJwfM