# Antennas Questions and Answers – Radio Wave Propagation – Modes of Propagation

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This set of Antennas Multiple Choice Questions & Answers (MCQs) focuses on “Radio Wave Propagation – Modes of Propagation”.

1. Up to which frequency the ground wave propagation is used?
a) 2MHz
b) 2GHz
c) 30MHz
d) 30GHz

Explanation: Ground wave propagation also known as surface wave propagation is used up to 2MHz. sky wave propagation is used at 2MHz to 30MHz.

2. In a ground wave propagation, which component of electric field is short circuited when it’s in contact by earth?
a) Horizontal
b) Vertical
c) Both horizontal and vertical
d) Neither horizontal nor vertical

Explanation: Any horizontal component of electric field which is in contact with earth is short circuited by earth. Usually ground wave propagation is done by vertical antennas so it is vertically polarized.

3. During ground wave propagation earth behaves like a __________
a) Leaky capacitor
b) Leaky Inductor
c) Series combination of capacitor and inductor
d) Parallel combination of capacitor and inductor

Explanation: Any horizontal component of electric field which is in contact with earth is short circuited by earth. So earth behaves like a leaky capacity. It forms a resistor in shunt with a capacitor.
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4. Sky wave propagation reflects the frequencies ___________
a) 2MHz
b) 2 MHz to 30MHz
c) 2 GHz to 30 GHz
d) 30 GHz to 50GHz

Explanation: Ground wave propagation also known as surface wave propagation is used up to 2MHz. sky wave propagation is used at 2MHz to 30MHz.

5. At what distance the sky wave propagation is present from the earth surface?
a) 50 to 400km
b) Below 50 km
c) 600 to 750km
d) 50 to 400 m

Explanation: Sky wave propagation also known as ionosphere propagation reflects the waves with frequency 2 to 30MHz. It is present at 50 to 400km from earth surface.

6. Space wave propagation reflects the waves with frequencies _________
a) Below 2 GHz
b) 2 to 30MHz
c) Above 30GHz
d) Above 30MHz

Explanation: Ground wave propagation also known as surface wave propagation is used up to 2MHz. sky wave propagation is used at 2MHz to 30MHz. Space wave propagation reflects frequencies above 30MHz.

7. Space wave propagates at which frequency band?
a) VHF
b) HF
c) MF
d) EHF

Explanation: Space wave propagation reflects frequencies at 30 to 300MHz range. So it propagates at VHF band.
MF- 300 KHz – 3MHz
EHF- 30GHz-300GHz

8. Communication through LOS can be increased by decreasing the height of antenna.
a) True
b) False

Explanation: Line of sight provides a direct communication link from transmitter to receiver. If the height of antennas is increased then the LOS is also improved.

9. In which of the following mode of propagation the waves are guided along the surface of the earth?
a) Ground wave
b) Sky wave
c) LOS
d) Space wave

Explanation: In ground wave or surface wave propagation the waves are guided along the surface of the earth. In sky wave they are reflected at different layers in the ionosphere. Space wave uses either direct or indirect method of propagation from transmitter to receiver directly.

10. In which of the following modes of propagation the ionosphere acts as the reflecting surface for the waves?
a) Ground wave
b) Sky wave
c) Space wave
d) LOS

Explanation: In Sky wave or Ionospheric wave propagation waves are reflected from the ionosphere layers depending upon different frequencies.

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