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Radio waves always
travel in straight lines
travel in straight lines but can be diffracted or reflected
travel in straight lines but can be diffracted
travel in straight lines but can be reflected
As they spread out from the transmitter radio waves
get stronger
get weaker
stay the same strength
will vary in strength depending on reflection from the ionosphere
When operating a transmitter with an indoor antenna
glass absorbs less RF than bricks
glass absorbs more RF than bricks
glass and bricks absorb the same amount of RF energy
glass and bricks absorb no RF energy
To improve the range of a VHF transmitter and receiver the best results are achieved by:
Increasing the power of the transmitter
Increasing the height of the antenna
Increase the filtering of the transmitter/receiver
Increase the audio gain of the receiver
Which of these bands would be most effective in transmitting a VHF/UHF signal over a long distance? Assume that they all have the same power, antennas at the same height, dipole antennas cut to the frequency of operation. Assume that only the ground wave is involved
4m band
2m band
70cm band
23 cm band
Layers of the ionosphere lie between
10 to 70 miles above the ground
10 to 70 km above the ground
70-400miles above the ground
70 - 400km above the ground
Which of these frequencies mainly depend on the ionosphere for communication?
VHF
UHF
HF
Frequencies below 200kHz
Which of these factors do not affect reflection from the ionosphere
Time of day
Seasons of year
Day of the week
Frequency
Which of these is true?
The ionospheric layers remain at the same height
The ionospheric layers always have the same thickness
The ionospheric layers can only reflect or refract signals
The ionospheric layers become ionised because of light from the sun