Physical Processes 2 RNAV

One of the more difficult yet fundamental parts of Radio Navigation is understanding how the different frequencies dictate how the wave changes in terms of direction and strength.

• For diffraction, as the wavelength gets closer to the size of the earth, it will diffract more readily. Hence, this happens more at lower frequencies with larger wavelengths.
• For refraction, the change of speed encountered when moving into another medium will be more at lower frequencies, hence giving a larger change in direction, and hence more refraction.
• For attenuation, high frequencies are scattered more readily in the atmosphere. In the ionosphere, however, the case is the opposite as high wavelengths will move the charged ions further, causing more collisions and therefore more loss of signal strength.
• For reflection, the efficiency of reflection is a function of both target size and wavelength. Reflection is more efficient when the wavelength is close to the target size. Therefore, this cannot simply be determined by an increase or decrease. This is an important consideration with radar, especially airborne weather radar.