US_TECH_2022_2026
Technician 2022-2026 - Radio wave propagation
Radio wave propagation groups the T3 section questions for focused review and easier weak-point tracking.
34
Questions
9
Sibling Topics
- Pool
- Technician 2022-2026
- Questions
- 34
- Topic
- Radio wave propagation
- Region
- US
Read the condition in the stem before comparing key terms in the options.
Study rules, calculations, and equipment questions as separate patterns.
After this topic, return to the full pool for mixed practice.
Topic Study Guide
This topic focuses on the physical properties of radio waves, the wavelength-frequency conversion formula, and how HF, VHF, and UHF bands propagate through different environments like the ionosphere, vegetation, and precipitation.
High-Yield Checks
- Wavelength and frequency conversion: Wavelength (meters) = 300 / Frequency (MHz). They are inversely proportional.
- Frequency band ranges: HF (3-30 MHz), VHF (30-300 MHz), UHF (300-3000 MHz).
- Polarization: Determined by the electric field. VHF/UHF line-of-sight requires matched polarization (horizontal for CW/SSB), while ionospheric skywaves are elliptically polarized and do not require matching.
- Multipath propagation: Causes "picket fencing" in mobile signals, irregular fading in HF, and increased error rates in data transmissions.
- Environmental effects: Vegetation absorbs UHF and microwaves; precipitation affects microwaves; the ionosphere refracts HF and VHF waves.
Trap Patterns
- Confusing frequency ranges, especially mixing up VHF (30-300 MHz) with UHF (300-3000 MHz).
- Assuming mismatched polarization causes echoes or inverted sidebands, when it actually just severely reduces received signal strength.
- Believing fog and rain severely affect the 10-meter and 6-meter bands, when in fact they have little effect.
- Misunderstanding electromagnetic wave structure by choosing parallel fields; the correct answer is they are at right angles.
Review Steps
- Memorize the wavelength formula (300 divided by frequency in MHz) and the exact ranges for HF, VHF, and UHF.
- Understand the basic components of electromagnetic waves (electric and magnetic fields at right angles) and that they travel at the speed of light in free space.
- Contrast line-of-sight propagation (VHF/UHF, highly affected by polarization and multipath) with ionospheric propagation (HF, elliptically polarized, relies on refraction).
- Summarize how physical obstacles (buildings, trees, precipitation) specifically affect different frequencies (e.g., reflection, absorption).
Quick Checks
- What is the formula to convert frequency in MHz to wavelength in meters?
- Which atmospheric layer is responsible for refracting HF and VHF radio waves?
- What happens if antennas at opposite ends of a VHF line-of-sight link are not using the same polarization?
- What is the frequency range for the VHF band?
Questions in This Topic
Choose Practice ModeT3A01Why do VHF signal strengths sometimes vary greatly when the antenna is moved only a few feet?T3A02What is the effect of vegetation on UHF and microwave signals?T3A03What antenna polarization is normally used for long-distance CW and SSB contacts on the VHF and UHF bands?T3A04What happens when antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization?T3A05When 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?T3A06What is the meaning of the term “picket fencing”?T3A07What weather condition might decrease range at microwave frequencies?T3A08What is a likely cause of irregular fading of signals propagated by the ionosphere?T3A09Which of the following results from the fact that signals propagated by the ionosphere are elliptically polarized?T3A10What effect does multi-path propagation have on data transmissions?T3A11Which region of the atmosphere can refract or bend HF and VHF radio waves?T3A12What is the effect of fog and rain on signals in the 10 meter and 6 meter bands?T3B01What is the relationship between the electric and magnetic fields of an electromagnetic wave?T3B02What property of a radio wave defines its polarization?T3B03What are the two components of a radio wave?T3B04What is the velocity of a radio wave traveling through free space?T3B05What is the relationship between wavelength and frequency?T3B06What is the formula for converting frequency to approximate wavelength in meters?T3B07In addition to frequency, which of the following is used to identify amateur radio bands?T3B08What frequency range is referred to as VHF?T3B09What frequency range is referred to as UHF?T3B10What frequency range is referred to as HF?T3B11What is the approximate velocity of a radio wave in free space?T3C01Why are simplex UHF signals rarely heard beyond their radio horizon?T3C02What is a characteristic of HF communication compared with communications on VHF and higher frequencies?T3C03What is a characteristic of VHF signals received via auroral backscatter?T3C04Which 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?T3C05Which of the following effects may allow radio signals to travel beyond obstructions between the transmitting and receiving stations?T3C06What type of propagation is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?T3C07What band is best suited for communicating via meteor scatter?T3C08What causes tropospheric ducting?T3C09What is generally the best time for long-distance 10 meter band propagation via the F region?T3C10Which of the following bands may provide long-distance communications via the ionosphere’s F region during the peak of the sunspot cycle?T3C11Why is the radio horizon for VHF and UHF signals more distant than the visual horizon?
More Topics
FCC rules, station licensing, and operator dutiesOperating procedures and emergency communicationsStation setup and equipment operationElectrical principles and mathElectronic components and circuitsPractical circuits, troubleshooting, and measurementsSignals, emissions, and modulationAntennas and feed linesElectrical, RF, and mechanical safety