Why do AM stations power down at night?

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Tags

1. #however
2. #nighttime
3. #cease
4. #order
5. #during
6. #required
7. #miles
8. #night
9. #called
10. #signals
11. #skywave
12. #rules
13. #avoid
14. #stations
15. #phenomenon
16. #reduce
17. #hours
18. #reflection
19. #travel
20. #other
21. #operating
22. #ionosphere
23. #hundreds
24. #their
25. #radio
26. #propagation
27. #interference
28. #power