Ham Radio General Class Test Radio Wave Propagation 3 — Questions and Answers
Question 1: What is the 'skip zone' in HF propagation?
- The area of strongest signal directly below the transmitting antenna
- The region between the end of ground-wave coverage and the point where sky-wave returns to Earth (Correct answer)
- The altitude range within the ionosphere where refraction occurs
- A geographic area with high atmospheric noise
Correct answer: The region between the end of ground-wave coverage and the point where sky-wave returns to Earth
The skip zone is the area of no usable signal between where ground-wave fades out and where the first sky-wave hop returns to Earth.
Question 2: What is 'multipath propagation' and what audio effect does it cause?
- Propagation via multiple antenna elements causing stronger signals
- Signals arriving via different ionospheric paths causing selective fading and distortion (Correct answer)
- Ground reflection that adds 6 dB of gain to a signal
- Multiple hops that add time delay to digital signals only
Correct answer: Signals arriving via different ionospheric paths causing selective fading and distortion
Multipath propagation occurs when signals arrive via different paths with different delays, causing phase cancellation, selective fading, and audio distortion.
Question 3: How does the 11-year solar cycle affect HF propagation on the higher bands (15, 10 meters)?
- Solar maximum degrades 15 and 10 meter propagation due to increased D-layer absorption
- Near solar maximum, higher ionization raises the MUF, making 15 and 10 meters highly active for DX (Correct answer)
- The solar cycle only affects propagation below 7 MHz
- Solar minimum is the best time for 10-meter worldwide propagation
Correct answer: Near solar maximum, higher ionization raises the MUF, making 15 and 10 meters highly active for DX
Near solar maximum, increased F-layer ionization raises the MUF above 28 MHz, opening the 10-meter band to worldwide propagation that may be absent at solar minimum.
Question 4: What causes 'long-path' propagation and how does it differ from 'short-path'?
- Long-path uses the shorter great-circle route; short-path uses the longer route
- Long-path uses the longer great-circle route (the other way around the globe) and can offer cleaner signals (Correct answer)
- Long-path is only possible on frequencies below 14 MHz
- Long-path and short-path refer to single-hop vs. multi-hop propagation
Correct answer: Long-path uses the longer great-circle route (the other way around the globe) and can offer cleaner signals
Every great-circle path has two directions; the long-path goes the longer way around Earth and sometimes offers better propagation or unique signal characteristics.
Question 5: What is the typical one-way skip distance for a single F2-layer hop?
- 50-200 km
- 200-500 km
- 1,000-3,000 km (Correct answer)
- 5,000-8,000 km
Correct answer: 1,000-3,000 km
A single F2 hop typically spans 1,000 to 3,000 km, and multiple hops can extend this range to cover intercontinental distances.
Question 6: What ionospheric phenomenon is associated with geomagnetic storms and degraded HF communications at high latitudes?
- Sporadic-E enhancement
- Polar cap absorption (PCA) (Correct answer)
- Tropospheric ducting
- Ionospheric tilt
Correct answer: Polar cap absorption (PCA)
Polar cap absorption occurs when energetic solar protons penetrate the polar ionosphere and dramatically increase D-layer absorption, blacking out HF communications at high latitudes.
Question 7: Which factor most determines whether a given frequency will be refracted back to Earth or will pass through the ionosphere into space?
- Antenna polarization
- Whether the frequency is above or below the Maximum Usable Frequency (MUF) (Correct answer)
- Transmitter power level
- Time of day relative to the local noon
Correct answer: Whether the frequency is above or below the Maximum Usable Frequency (MUF)
Frequencies above the MUF pass through the ionosphere into space and are not returned to Earth, while frequencies below the MUF are refracted back.
Ham Radio General Class Test Radio Wave Propagation 3
What is the 'skip zone' in HF propagation?