Basic Radio Wave Propagation

• Flight Radio Telephony is the study of how to operate the aircraft's radio.
• In aviation Very High Frequency (VHF) is used.

Radio Waves

• Radio waves do not require a medium to work in.
• This means that they can travel not only through air and solid materials, but also through the vacuum of space, and travel at the speed of light (300,000 Km/sec)
• Electromagnetic (radio) waves propagate outward from a source by causing alternate increases and decreases in the electrical field and the magnetic field at the same time.
• We use changes in the electrical fields to send out and receive radio waves.
• Dropping a stone in a pond and watching a cork in the water move up and down on the resulting waves moving outwards is a good analogy for this.

Frequency

• The number of complete waves that will travel past a point in one second. 
• It is measured in Hertz.

Amplitude

• The distance from the base line to the highest point of a peak (or lowest point of a trough).
• Generally measured in volts (being the maximum change in the electrical field).

Wavelength

• The length of a single wave.
• The distance travelled by the wave during transmission of one cycle.
• Because the speed of light is constant, if you increase the wavelength then less of the waves will pass a point each second, so the frequency must be lower.
• Radio waves may be reflected, refracted (bent), attenuated (weakened), absorbed or diffracted (scattered).
• Thus they are subject to terrain and atmospheric interference.