Leason 3: Radio Wave Characteristics

Question 1

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

A. Backscatter

B. Sporadic E

C. D layer absorption

D. Gray-line propagation

Answer 1

B. Sporadic E

Sometimes you will hear amateur stations located past the horizon on 10 meters, 6 meters and 2 meters with strong signals. These over-the-horizon signals are being reflected by the E layer of the atmosphere. This propagation type is called sporadic E.

Question 2

What weather condition might decrease range at microwave frequencies?

A. High winds

B. Low barometric pressure

C. Precipitation

D. Colder temperatures

Answer 2

C. Precipitation

Question 3

Which of the following results from the fact that signals propagated by the ionosphere are elliptically polarized?

Answer 3

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

Question 4

What is the relationship between the electric and magnetic fields of an electromagnetic wave?

A. They travel at different speeds

B. They are in parallel

C. They revolve in opposite directions

D. They are at right angles

Answer 4

D. They are at right angles.

Notes: A radio wave has two components: the electric and magnetic fields. The two fields of an electromagnetic wave are at right angles to each other.

Question 5

What is the approximate velocity of a radio wave in free space?

A. 150,000 meters per second

B. 300,000,000 meters per second

C. 300,000,000 miles per hour

D. 150,000 miles per hour

Answer 5

B. 300,000,000 meters per second

Question 6

What is the effect of vegetation on UHF and microwave signals?

Answer 6

Absorption.

Question 7

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

Answer 7

Try to find a path that reflects signals to the repeater.

Question 8

What property of a radio wave defines its polarization?

Answer 8

The orientation of the electric field.

Question 9

Why are simplex UHF signals rarely heard beyond their radio horizon?

Answer 9

UHF signals are usually not propagated by the ionosphere.

Question 10

What band is best suited for communicating via meteor scatter?

A. 33 centimeters

B. 6 meter band

C. 2 meter band

D. 70 centimeter band

Answer 10

B. 6 meter band.

Communications via meteor scatter occurs when radio waves are reflected back to Earth from the ionized atmosphere because meteorites are entering Earth’s atmosphere and burning up on entry. The 6-meter, or 50 MHz, band is excellent for meteor scatter communications because of its wavelength.

Question 11

What are the two components of a radio wave?

A. Impedance and reactance

B. Voltage and current

C. Electric and magnetic fields

D. Ionizing and non-ionizing radiation

Answer 11

C. Electric and magnetic fields

Question 12

What is the effect of fog and rain on signals in the 10 meter and 6 meter bands?

A. Absorption

B. There is little effect

C. Deflection

D. Range increase

Answer 12

B. There is little effect

Question 13

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

A. Knife-edge diffraction

B. Faraday rotation

C. Quantum tunneling

D. Doppler shift

Answer 13

A. Knife-edge diffraction

Question 14

What is a characteristic of HF communication compared with communications on VHF and higher frequencies?

A. HF antennas are generally smaller

B. HF accommodates wider bandwidth signals

C. Long distance ionospheric propagation is far more common on HF

D. There is less atmospheric interference (static) on HF

Answer 14

C. Long distance ionospheric propagation is far more common on HF

Notes: The amateur radio VHF and UHF and above bands are mostly for communications with other stations that are within line of sight. These bands depend on repeaters to increase their effective range. The HF bands are well suited for long-range communications because their radio waves are reflected back toward earth instead of punching through the ionosphere. The ability of HF frequencies to bounce off the ionosphere and provide long-distance propagation is far more common.

Question 15

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

A. Wavelength in meters equals frequency in hertz multiplied by 300

B. Wavelength in meters equals frequency in hertz divided by 300

C. Wavelength in meters equals frequency in megahertz divided by 300

D. Wavelength in meters equals 300 divided by frequency in megahertz

Answer 15

D. Wavelength in meters equals 300 divided by frequency in megahertz.

Notes:
Remember, on the FCC exam you are asked to pick the most correct answer, so 2.047474 meters is closer to 2 meters than 20 meters.

Question 16

What is the relationship between wavelength and frequency?

A. The wavelength gets longer as the frequency increases

B. The wavelength gets shorter as the frequency increases

C. Wavelength and frequency are unrelated

D. Wavelength and frequency increase as path length increases

Answer 16

B. The wavelength gets shorter as the frequency increases

Question 17

What is the meaning of the term “picket fencing”?

A. Alternating transmissions during a net operation

B. Rapid flutter on mobile signals due to multi-path propagation

C. A type of ground system used with vertical antennas

D. Local vs long-distance communications

Answer 17

B. Rapid flutter on mobile signals due to multi-path propagation

Question 18

What effect does multi-path propagation have on data transmissions?

A. Transmission rates must be increased by a factor equal to the number of separate paths observed

B. Transmission rates must be decreased by a factor equal to the number of separate paths observed

C. No significant changes will occur if the signals are transmitted using FM

D. Error rates are likely to increase

Answer 18

D. Error rates are likely to increase

Question 19

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

A. Right-hand circular

B. Left-hand circular

C. Horizontal

D. Vertical

Answer 19

C. Horizontal

Question 20

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

A. Tropospheric ducting

B. D layer refraction

C. F2 layer refraction

D. Faraday rotation

Answer 20

A. Tropospheric ducting

Question 21

What frequency range is referred to as VHF?

A. 30 kHz to 300 kHz

B. 30 MHz to 300 MHz

C. 300 kHz to 3000 kHz

D. 300 MHz to 3000 MHz

Answer 21

B. 30 MHz to 300 MHz

Question 22

What frequency range is referred to as HF?

A. 300 to 3000 MHz

B. 30 to 300 MHz

C. 3 to 30 MHz

D. 300 to 3000 kHz

Answer 22

C. 3 to 30 MHz

Question 23

What frequency range is referred to as UHF?

A. 30 to 300 kHz

B. 30 to 300 MHz

C. 300 to 3000 kHz

D. 300 to 3000 MHz

Answer 23

D. 300 to 3000 MHz

The UHF (ultra high frequency) radio spectrum refers to radio waves with a frequency of 300 MHz (megahertz) to 3 GHz (gigahertz). Sometimes you will see 3 GHz referred to as the “decimeter band.” Wavelengths in the UHF radio spectrum range from one meter to one tenth of a meter (one decimeter).

Question 24

What causes tropospheric ducting?

A. Discharges of lightning during electrical storms

B. Sunspots and solar flares

C. Updrafts from hurricanes and tornadoes

D. Temperature inversions in the atmosphere

Answer 24

D. Temperature inversions in the atmosphere