# Antennas Questions and Answers – Space Wave Propagation – Tropospheric Scatter

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

1. What is the frequency at which tropospheric scatter occurs?
a) Above 30MHz
b) Below 30 MHz
c) < 3MHz
d) > 3 MHz and < 30MHz

Explanation: Tropospheric scatter is also known as forward scatter propagation. It occurs at a frequency above 30MHz. It belongs to the UHF and microwave range.

2. What is the range of frequency at which tropospheric scatter occurs?
a) UHF and Microwave range
b) HF
c) MF and VHF
d) MF and HF

Explanation: Tropospheric scatter occurs at a frequency above 30MHz. It belongs to the UHF and microwave range.
MF- 300 KHz – 3MHz
HF – 3 to 30 MHz
VHF -30 to 300MHz.

3. Tropospheric propagation is also known as forward scatter propagation.
a) True
b) False

Explanation: Tropospheric scatter is also known as forward scatter propagation, occurs at a frequency above 30MHz. It belongs to the UHF and microwave range. Its scattering occurs above radio horizon and travels beyond the LOS.

4. The tropospheric scattering occurs at _________
a) Beyond the LOS
b) In ground wave propagation
c) In sky wave propagation
d) Below the radio horizon

Explanation: Tropospheric scattering occurs at a frequency above 30MHz. So, this occurs in space wave propagation. Signal scatters in forward direction above the radio horizon and it travels beyond the LOS. Ground wave propagation occurs at less the 2MHz and sky wave at 2 to 30 MHz frequency.

5. Tropospheric scattering, if falls under low frequencies then it leads to Ionosphere scattering.
a) True
b) False

Explanation: The tropospheric scattering occurs at frequency above 30MHz. Under low frequencies it falls below 30MHz and sometimes thus leads to the Ionospheric propagation.
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6. The turbulences in the atmosphere lead to ___________
a) tropospheric scattering
b) ground wave propagation
c) sky wave propagation
d) constant velocity of signal

Explanation: The main cause of the tropospheric scattering is the turbulences in the atmosphere. When it meets the turbulences, then there will be an abrupt change in velocity leading to the tropospheric scattering.The tropospheric scattering occurs at frequency above 30MHz.

7. When the signal take-off angle increases, the height of scatter volume ________
a) increases
b) decreases
c) it remains constant
d) may increase or decrease

Explanation: The signal take-off angle determines the height of the scatter volume. As the signal take-off angle increases, the height of scatter volume also increases. A low take-off produces low scatter volume.

8. Which of the following statements regarding tropospheric scattering is false?
a) It occurs in the region near to the mid-point of the transmitter and receiver
b) It occurs above the radio horizon
c) It travels beyond the line of sight distance
d) It occurs below the radio horizon

Explanation: Signal scatters in forward direction above the radio horizon and it travels beyond the LOS. It occurs in the region near to the mid-point of the transmitter and receiver.

9. In tropospheric scattering, rapid fading occurs due to _______ and long-term fading occurs due to ______
a) multipath propagation, turbulences in atmosphere
b) low signal strength, signal travelling below horizon
c) signal travelling below horizon, low signal strength
d) daily and seasonal variations, multi-path propagation

Explanation: Rapid fading occurs due to the multipath propagation. As the turbulent conditions changes constantly, the path length and signal strength levels also change. The turbulence in the atmosphere gives rise to daily and seasonal variations in signal strength so results in long-term fading.

10. Which of the following is used for communication in rugged terrain where normal propagation methods fail?
a) Tropospheric Scattering
b) Ground wave
c) LOS

Explanation: Signal scatters in forward direction above the radio horizon and it travels beyond the LOS. The signal strength is decreased as only a small amount of it is forward scattered and so high power amplifiers are equipped at the receivers.

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