In investigating the possibilities of short-wave radio the surprising fact was discovered that although short waves may often be clearly received at distances of thousands of miles from stations with very little power, it is difficult or impossible to detect them at nearby points, 30 to 300 miles away. This can be understood if the upper atmosphere acts like a reflector.
©1931 by Iowa State Teachers College
"Radio and the Outer Atmosphere,"
Science Bulletin: Vol. 3:
5, Article 6.
Available at: https://scholarworks.uni.edu/science_bulletin/vol3/iss5/6