062.01 BASIC RADIO PROPAGATION THEORY

Question 1

Both a primary and secondary radar system use a (omni-directional/directional) antenna for transmitting and a (omni-directional/directional)​ antenna for receiving.

Answer 1

Both a primary and secondary radar system use a (directional) antenna for transmitting and a (directional) antenna for receiving.

Question 2

The phenomenon when a radio wave bends when it passes around an impenetrable obstacle is (…)​.

Answer 2

The phenomenon when a radio wave bends when it passes around an impenetrable obstacle is (diffraction).

Question 3

In accordance with the ITU, a radio signal may be classified by three symbols. Second symbol indicates (e.g. A1A) (…)​.

Answer 3

In accordance with the ITU, a radio signal may be classified by three symbols. Second symbol indicates (e.g. A1A) (nature of signal).

Question 4

(…) is the bending of its propagation path as it passes through or over areas of different electrical conductivity.

Answer 4

(Refraction) is the bending of its propagation path as it passes through or over areas of different electrical conductivity resulting in a change of speed.

Question 5

Speed of light (c) equals (…) m/s.

Answer 5

Speed of light (c) equals (300 000 000) m/s.

Question 6

For an antenna to transmit an electromagnetic wave, a(n) (alternating/direct) current is necessary.

Answer 6

For an antenna to transmit an electromagnetic wave, a(n) (alternating) current is necessary.

Question 7

Modulation means addition of a (low/high) frequency signal (tone, voice) onto a (low/high) ​frequency carrier wave.

Answer 7

Modulation means addition of a (low) frequency signal (tone, voice) onto a (high) frequency carrier wave.

Question 8

In accordance with the ITU, a radio signal may be classified by three symbols. First symbol indicates (e.g. A1A) (…)​.

Answer 8

In accordance with the ITU, a radio signal may be classified by three symbols. First symbol indicates (e.g. A1A) (type of modulation of the main carrier).

Question 9

Keying means interrupting the (modulating signal/carrier wave) to break it into dots and dashes.

Answer 9

Keying means interrupting the (carrier wave) to break it into dots and dashes.

Question 10

Reflection from ionospheric layers is used in (HF/VHF/UHF/SHF) radio frequencies.

Answer 10

Reflection from ionospheric layers is used in (HF) radio frequencies.

Question 11

The phenomenon of a change in the direction of a radio wave occurring as it reaches the boundary between two different media is called (…)​.

Answer 11

The phenomenon of a change in the direction of a radio wave occurring as it reaches the boundary between two different media is called (reflection).

Question 12

The electrical component (E) is always (parallel/perpendicular) with the transmitter and the magnetic component (H) is always (parallel/perpendicular)​ to the transmitter.

Answer 12

The electrical component (E) is always (parallel) with the transmitter and the magnetic component (H) is always (perpendicular) to the transmitter.

Question 13

In accordance with the ITU, a radio signal may be classified by three symbols. Third symbol indicates (e.g. A1A) (…)​.

Answer 13

In accordance with the ITU, a radio signal may be classified by three symbols. Third symbol indicates (e.g. A1A) (nature of information).

Question 14

A radio signal loses strength as the range from the transmitter increases. This effect is called (…)​.

Answer 14

A radio signal loses strength as the range from the transmitter increases. This effect is called (attenuation).

Question 15

A flat plate (slotted) antenna generates (more/less) ​side lobes than the parabolic reflector.

Answer 15

A flat plate (slotted) antenna generates (less) side lobes than the parabolic reflector.

Question 16

Polarization is the orientation of the plane of oscillation of the (magnetic/electrical)​ compontent of the electromagnetic wave.

Answer 16

Polarization is the orientation of the plane of oscillation of the (electrical) compontent of the electromagnetic wave.

Question 17

State whether the following antennae are directional or omni-directional:

• Loop
• Helical
• Sense
• Parabolic
• Slotted planar
• Dipole

Answer 17

State whether the following antennae are directional or omni-directional:

• Loop → directional
• Helical → directional
• Sense → omni-directional
• Parabolic → directional
• Slotted planar → directional
• Dipole → omni-directional

Question 18

The process by which the radio wave energy is taken up by the atmosphere is called (…)​.

Answer 18

The process by which the radio wave energy is taken up by the atmosphere is called (absorption).

Question 19

The superimposition of two radio waves of the same or nearly the same frequency is called (…)​.

Answer 19

The superimposition of two radio waves of the same or nearly the same frequency is called (interference).