Free HAM Radio Extra Class Test Radio Wave Propagation Questions and Answers

Question 1

Which of the following atmospheric conditions is most likely to cause tropospheric ducting of VHF and UHF signals?

Accepted Answer

A temperature inversion over a large body of water.

Answer

Tropospheric ducting occurs when a layer of warm air sits on top of a layer of cooler air, a condition known as a temperature inversion. This inversion creates a 'duct' that can trap VHF and UHF radio waves, causing them to travel much farther than the normal line-of-sight distance. This phenomenon is often observed over large bodies of water, especially during stable, high-pressure weather conditions.

Question 2

An amateur operator is attempting a long-distance contact on the 160-meter band. Which propagation mode offers the best chance for success when both the transmitting and receiving stations are located along the terminator?

Accepted Answer

Gray-line propagation

Answer

Gray-line propagation occurs along the terminator, which is the line separating daylight from darkness. Around sunrise and sunset, the D-layer of the ionosphere, which normally absorbs lower HF frequencies, rapidly disappears, while the F-layer remains ionized. This creates a short-lived but very efficient path for long-distance communication on the lower bands, such as 160, 80, and 40 meters.

Question 3

A characteristic distortion of signals propagated via aurora, often described as a 'raspy' or 'buzzing' sound on CW and SSB signals, is primarily caused by what phenomenon?

Accepted Answer

Rapid and random phase shifts from moving ionized particles.

Answer

Auroral propagation involves scattering signals off the moving, ionized curtains of an aurora. The rapid movement and changing density of the ionized particles cause rapid and random phase shifts in the reflected signal. This phenomenon results in a Doppler spread, which is perceived as a distinctive flutter, buzz, or raspy distortion on the received audio.

Question 4

For which of the following scenarios would Near Vertical Incidence Skywave (NVIS) propagation be most suitable?

Accepted Answer

Establishing reliable communication between two stations 50 miles apart in mountainous terrain on 80 meters.

Answer

NVIS is a propagation mode that uses high-angle radiation to send signals almost straight up to be reflected by the ionosphere. This provides reliable communication over short to medium distances, typically from 0 to about 400 miles, and is particularly effective at overcoming line-of-sight obstacles like mountains. It works best on lower HF bands, such as 160, 80, and 40 meters.

Question 5

Which of the following describes a key characteristic of transequatorial propagation (TEP) on the 6-meter and 2-meter bands?

Accepted Answer

It often occurs in the late afternoon or early evening between stations equidistant from the magnetic equator.

Answer

Transequatorial propagation (TEP) is a phenomenon that allows for long-distance communication on VHF bands between stations located on opposite sides of, and roughly equidistant from, the magnetic equator. It is most common during periods of high solar activity, especially around the spring and autumn equinoxes, during the late afternoon and early evening hours.

HAM - Radio Extra Class Test Practice Test

HAM - Radio Extra Class Test Practice Test

Free HAM Radio Extra Class Test Radio Wave Propagation Questions and Answers