Nature of the information to be transmitted.

 

2                   

Type of modulation of the secondary carrier.

 

3                   

Type of modulation of the main carrier.

 

4                   

Nature of signal(s) modulating the main carrier.

 

 

Вопрос 4

The term "Keying" means:

 

 

Ответы

1                   

changing the amplitude of the carrier wave to add information.

 

2                   

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

 

3              

Interrupting the carrier wave to break it into dots and dashes.

 

4                   

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

 

 

Вопрос 5

The radio wave energy is taken up by the atmosphere. This process is called?

 

 

Ответы

1                   

interference

 

2              

Absorption

 

3                   

refraction

 

4                   

diffraction

 

 

Вопрос 6

The wavelength of a radio signal transmitted at the frequency 116,7 MHz

 

 

Ответы

1                   

2,53m

 

2              

M

 

3                   

25,3m

 

4                   

25,7cm

 

Вопрос 7

An apparent decreasa in the transmitted frequency which is proportional to the transmitter velocity will occur when:

 

 

Ответы

1                   

the receiver moves towards the transmitter.

 

2                   

both transmitter and receiver move towards each other.

3              

The transmitter moves away from the receiver.

 

4                   

the transmitter moves towards the receiver.

 

 

Вопрос 8

Diffraction is the process by which:

 

 

Ответы

1              

Radio wave travel over and around obstacles.

 

2                   

a ground wave is attenuated over rough ground.

 

3                   

a space wave penetrates the ionosphere.

 

4                   

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

 

 

Вопрос 9

To establish and maintain effective HF communications the frequency used at a given range:

 

 

Ответы

1                   

should be increased at night.

 

2                   

should remain constant.

 

3                   

should only be varied by season, decreased in summer and increased in winter.

 

4              

Should be decreased at night.

 

 

Вопрос 10

An electromagnetic wave consists of an oscillating electric field (E) and an oscillating magnetic field (H). Which statement is correct?

 

 

Ответы

1                   

when signal passes through the antenna, the "E" field is perpendicular to the wire and the "H" field is parallel to the wire.

 

2                   

a dipole antenna can only transmit the "H" field.

 

3                   

when signal passes through the antenna, the "E" and "H" fields are perpendicular to to the wire.

 

4              

when signal passes through the antenna, the "H" field is perpendicular to the wire and the "E" field is parallel to the wire.

 

Вопрос 11

Polarisation of an electromagnetic wave describes:

 

 

Ответы

1              

The orientation of the plane of oscillation of the electrical component of the wave with regard to its direction of propagation.

 

2                   

the loss of power of the electrical component of the electromagnetic wave.

 

3                   

the orientation of the plane of oscillation of the magnetic component of the wave with regard to its direction of propagation.

 

4                   

the direction of propagation.

 

Вопрос 12

The electromagnetic waves refracted from the E and F layers of the ionosphere are called:

 

 

Ответы

1                   

space waves

 

2              

Sky waves

 

3                   

refracted waves

 

4                   

ground waves

 

 

Вопрос 13

With regard to radio waves propagation, a "cycle" is defined

 

 

Ответы

1              

A complete series of values of a periodical process.

 

2                   

the length of the pulse.

 

3                   

a number of oscillations per second.

 

4                   

the distance covered by a radio wave in one second.

 

 

Вопрос 14

Change in the direction of a radio wave occurring as it reaches the boundary between two different media is called:

 

 

Ответы

1                   

diffraction.

 

2                   

interference.

 

3              

Reflection.

 

4                   

attenuation.

 

 

Вопрос 15

Comparing a parabolic reflector with a flat plate antenna of the same size

 

 

Ответы

1                   

the flat plate antenna has a considerably smaller beam width.

 

2              

The flat plate antenna generates less side lobes than the parabolic reflector.

 

3                   

the parabolic reflector generates less side lobes than the flat plate antenna.

 

4                   

the parabolic reflector has a considerably smaller beam width.

 

 

Вопрос 16

"Modulation" means:

 

 

Ответы

1                   

Addition of a high frequency signal (tone, voice) onto low frequency carrier wave

 

2                   

Elimination of disturbances for improving reception

 

3                   

Tuning receiver into the frequency of the transmitter

 

4              

Addition of a low frequency signal (tone, voice) onto high frequency carrier wave

 

 

Вопрос 17

In accordance with the ITU (International Telecommunication Union) a radio signal may be classified by three symbols. First symbol indicates

 

(e.g. A1A):

 

 

Ответы

1                   

Type of modulation of the secondary carrier.

 

2                   

Nature of the information to be transmitted.

 

3