Sub-Element T3 Radio wave characteristics: Properties of radio waves; propagation modes [3 Exam Questions]

Question 1

What should you do if another operator reports that your station’s 2 meter signals were strong just a moment ago, but now they are weak or distorted?

Answer 1

Try moving a few feet or changing the direction of your antenna if possible, as reflections may be causing multi-path distortion

Question 2

Why might the range of VHF and UHF signals be greater in the winter?

Answer 2

Less absorption by vegetation

Question 3

What antenna polarization is normally used for long-distance weak-signal CW and SSB contacts using the VHF and UHF bands?

Answer 3

Horizontal

Question 4

What can happen if the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization?

Answer 4

Signals could be significantly weaker

Question 5

When using a directional antenna, how might your station be able to access a distant repeater if buildings or obstructions are blocking the direct line of sight path?

Answer 5

Try to find a path that reflects signals to the repeater

Question 6

What term is commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting?

Answer 6

Picket fencing

Question 7

What type of wave carries radio signals between transmitting and receiving stations?

Answer 7

Electromagnetic

Question 8

Which of the following is a likely cause of irregular fading of signals received by ionospheric reflection?

Answer 8

Random combining of signals arriving via different paths

Question 9

Which of the following results from the fact that skip signals refracted from the ionosphere are elliptically polarized?

Answer 9

Either vertically or horizontally polarized antennas may be used for transmission or reception

Question 10

What may occur if data signals arrive via multiple paths?

Answer 10

Error rates are likely to increase

Question 11

Which part of the atmosphere enables the propagation of radio signals around the world?

Answer 11

The ionosphere

Question 12

How might fog and light rain affect radio range on 10 meter and 6 meter bands?

Answer 12

Fog and light rain will have little effect on these bands

Question 13

What weather condition would decrease range at microwave frequencies?

Answer 13

Precipitation

Question 14

What is the name for the distance a radio wave travels during one complete cycle?

Answer 14

Wavelength

Question 15

What property of a radio wave is used to describe its polarization?

Answer 15

The orientation of the electric field

Question 16

What are the two components of a radio wave?

Answer 16

Electric and magnetic fields

Question 17

How fast does a radio wave travel through free space?

Answer 17

At the speed of light

Question 18

How does the wavelength of a radio wave relate to its frequency?

Answer 18

The wavelength gets shorter as the frequency increases

Question 19

What is the formula for converting frequency to approximate wavelength in meters?

Answer 19

Wavelength in meters equals 300 divided by frequency in megahertz

Question 20

What property of radio waves is often used to identify the different frequency bands?

Answer 20

The approximate wavelength

Question 21

What are the frequency limits of the VHF spectrum?

Answer 21

30 to 300 MHz

Question 22

What are the frequency limits of the UHF spectrum?

Answer 22

300 to 3000 MHz

Question 23

What frequency range is referred to as HF?

Answer 23

3 to 30 MHz

Question 24

What is the approximate velocity of a radio wave as it travels through free space?

Answer 24

300,000,000 meters per second

Question 25

Why are direct (not via a repeater) UHF signals rarely heard from stations outside your local coverage area?

Answer 25

UHF signals are usually not reflected by the ionosphere

Question 26

Which of the following is an advantage of HF vs VHF and higher frequencies?

Answer 26

Long distance ionospheric propagation is far more common on HF

Question 27

What is a characteristic of VHF signals received via auroral reflection?

Answer 27

The signals exhibit rapid fluctuations of strength and often sound distorted

Question 28

Which of the following propagation types is most commonly associated with occasional strong over-the-horizon signals on the 10, 6, and 2 meter bands?

Answer 28

Sporadic E

Question 29

Which of the following effects might cause radio signals to be heard despite obstructions between the transmitting and receiving stations?

Answer 29

Knife-edge diffraction

Question 30

What mode is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?

Answer 30

Tropospheric ducting

Question 31

What band is best suited for communicating via meteor scatter?

Answer 31

6 meter band

Question 32

What causes tropospheric ducting?

Answer 32

Temperature inversions in the atmosphere

Question 33

What is generally the best time for long-distance 10 meter band propagation via the F layer?

Answer 33

From dawn to shortly after sunset during periods of high sunspot activity

Question 34

Which of the following bands may provide long distance communications during the peak of the sunspot cycle?

Answer 34

6 or 10 meters

Question 35

Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations?

Answer 35

The Earth seems less curved to radio waves than to light