Finally , at radio wavelengths longer than 10 meters or so ( about 30 MHz ) , the air in the lower atmosphere remains transparent to radio .
Plasma in certain layers of the ionosphere begins to interact with radio waves ( see skywave ) .
Finally , at radio wavelengths longer than 10 meters or so ( about 30 MHz ) , the air in the lower atmosphere remains transparent to radio , but plasma in certain layers of the ionosphere begins to interact with radio waves ( see skywave ) .