Extra exam: radio wave propagation
EME, meteor scatter, transequatorial, grayline and long-path propagation. 39 questions, 10 at a time, starting with ones you haven't seen.
Rules to remember10 key radio wave propagation rulesShow the rules
- Tropospheric ducting commonly carries microwave signals about 100 to 300 miles. (p. 34)
- TEP links stations about 2,000 to 3,000 miles apart on a path crossing the geomagnetic equator at right angles. (p. 35)
- Transequatorial propagation can reach up to about 5,000 miles. (p. 35)
- TEP is most likely in the afternoon and early evening. (p. 35)
- 160 m signals are heavily absorbed by the daytime D layer, so long paths open when the whole path is dark. (p. 35)
- Long-path propagation shows up most often on 40 and 20 meters. (p. 35)
- Ground-wave losses rise with frequency, so ground-wave range shrinks as frequency increases. (p. 36)
- Sporadic-E occurs mostly in daylight, between sunrise and sunset. (p. 36)
- Rising A and K indices mean the geomagnetic field is becoming more disturbed. (p. 37)
- Slight refraction in the lower atmosphere bends VHF/UHF signals, so the radio horizon is about 15 percent farther than the visual horizon. (p. 38)
Taken from the explanations to checked practice questions; page numbers link to the official handbook.
Sample radio wave propagation questions
1.What is the approximate maximum separation measured along the surface of the Earth between two stations communicating by EME?
- A5,000 miles, if the moon is at perigee
- B12,000 miles, if the moon is "visible" by both stations
- C2,000 miles, if the moon is at perigee
- D2,000 miles, if the moon is at apogee
Show the answer
✓ B. 12,000 miles, if the moon is "visible" by both stations
Two EME stations can work each other whenever both can see the Moon, which allows separations up to about 12,000 miles, roughly half of Earth's circumference.
2.Which of the following signal paths is most likely to experience high levels of absorption when the Aindex or K-index is elevated?
- ANVIS
- BSporadic-E
- CTransequatorial
- DThrough the auroral oval
Show the answer
✓ D. Through the auroral oval
High A or K values bring geomagnetic disturbance and heavy absorption on paths through the auroral oval near the poles.
3.What is a typical range for tropospheric duct propagation of microwave signals?
- A1,200 miles
- B10 miles to 50 miles
- C100 miles to 300 miles
- D2,500 miles
Show the answer
✓ C. 100 miles to 300 miles
Tropospheric ducting commonly carries microwave signals about 100 to 300 miles.
4.What is chordal-hop propagation?
- APropagation across the geomagnetic equator
- BPropagation away from the great circle bearing between stations
- CSignals reflected back toward the transmitting station
- DSuccessive ionospheric refractions without an intermediate reflection from the ground
Show the answer
✓ D. Successive ionospheric refractions without an intermediate reflection from the ground
Chordal hop is a series of ionospheric refractions with no reflection from the ground between them.