RNAV 6

HF radiowaves travel:

• during daytime as ground and sky waves, and during nighttime as ground waves only.

• during daytime and night-time as sky waves and the range of the ground wave is very small.

• quasi optically.

• during daytime and at night as ground waves only.

The wavelength of a radio signal transmitted at a frequency of 3GHz is:

• 100cm

• 1cm

• 10cm

• 1m

Diffraction is the process by which:

• a space wave penetrates the ionosphere.

• a ground wave is attenuated over rough ground.

• radio wave travel over and around obstacles.

• a direct wave is bent around the form of the Earth.

The term Doppler shift refers to:

• the change in phase angle measured at the receiver.

• the value of attenuation measured at the receiver.

• the change in the speed measured at the receiver.

• the change in frequency measured at the receiver.

Due to Doppler effect an apparent decrease in the transmitted frequency, which is proportional to the transmitter's velocity, will occur when:

• the transmitter and receiver move towards each other.

• the transmitter moves away from the receiver.

• the transmitter moves toward the receiver.

• both transmitter and receiver move away from each other.

The term 'Keying' means:

• changing the amplitude of the carrier wave to add information.

• interrupting the carrier wave to break it into dots and dashes.

• interrupting the modulating signal to break it into dots and dashes.

• adding information on the carrier wave by the use of modulating signal.

Single Side Band (SSB) is used:

• in VHF transmissions to reduce transmission power.

• with NDB transmissions to reduce bandwidth.

• in HF two-way communication.

• with transmissions of the Meteorological Aerodrome Report (METAR).

Phase modulation:

• results in a change of amplitude of the carrier wave.

• is a modulation form used in ILS where the phase of the navigation signal is changed 90° or 150°.

• results in a change of polarisation of the modulated signal.

• is a modulation form used in GPS where the phase of the carrier wave is reversed.

What describes polarisation?

• Rotation of the antenna around a fixed axis.

• Orientation of the antenna to the North Pole.

• Orientation of the plane of oscillation of the magnetic component (H) of the electromagnetic wave.

• Orientation of the plane of oscillation of the electrical component (E) of the electromagnetic wave.

UHF (Ultra High Frequency) waves appear in the frequency spectrum:

• 3GHz-30GHz

• 30MHz-300MHz

• 3MHz-30MHz

• 300MHz-3000MHz