Signals That Don't Reflect
Shorter wavelength radio waves (such as VHF, UHF and microwaves) don't curve around the Earth or reflect from the ionosphere as they travel. The fact that they penetrate the ionosphere makes them very useful for long-distance communications. These signals can be transmitted from ground stations to satellites in orbit around the Earth. The satellites receive, boost and re-transmit the signal to other ground stations.
The Beauty of Geostationary Orbit
Satellites in geostationary orbit are very important in worldwide communications. These satellites take exactly 24 hours to orbit the Earth at an altitude of 22,300 miles. This means they hover in the sky always in view of a particular ground station. As few as 5 satellites in geostationary orbit can receive and send messages around the entire world.
Space Weather Effects
During periods of disturbed space weather, the ionosphere can be filled with small-scale size irregularities. Radio signals traversing the disturbed ionosphere are disrupted by these irregularities which cause phase and amplitude fluctuations in the signals. This problem is particularly bad at high latitudes in the region of the auroral ovals and in the equatorial region where ionospheric bubbles (not associated with solar disturbances) occur.