US_TECH_2026_2030
Technician 2026-2030 - Radio wave propagation
Radio wave propagation groups the T3 section questions for focused review and easier weak-point tracking.
35
Questions
9
Sibling Topics
- Pool
- Technician 2026-2030
- Questions
- 35
- 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 covers the physical properties of radio waves (wavelength, frequency, electromagnetic fields) and propagation behaviors across HF, VHF, and UHF bands, including multipath, polarization, and ionospheric reflection.
High-Yield Checks
- Wavelength and frequency are inversely related. Formula: Wavelength (meters) = 300 / Frequency (MHz).
- Frequency ranges: HF (3-30 MHz), VHF (30-300 MHz), UHF (300-3000 MHz).
- Electromagnetic waves consist of electric and magnetic fields at right angles. Polarization is determined by the electric field.
- VHF/UHF propagation: Vegetation absorbs signals; multipath causes "picket fencing" flutter on mobile signals and increases data error rates.
- The ionosphere reflects HF waves, causing irregular fading from random multipath combining. It creates elliptical polarization, so TX/RX antennas don't need matching polarization.
Trap Patterns
- Confusing VHF (30-300 MHz) with UHF (300-3000 MHz). Pay close attention to the number of zeros in the options.
- Assuming the Doppler effect causes dead spots. Dead spots are actually caused by multipath propagation cancellations.
- Thinking vegetation causes diffraction. In reality, vegetation absorbs UHF and microwave signals.
- Confusing the troposphere with the ionosphere. It is the ionosphere that reflects HF radio waves.
Review Steps
- Memorize the HF, VHF, and UHF frequency ranges, and practice using the "300 / f (MHz)" formula to calculate wavelength.
- Understand the physical structure of radio waves: electric and magnetic fields are at right angles, the electric field defines polarization, and they travel at the speed of light in free space.
- Compare how different environments affect VHF/UHF signals, such as absorption by vegetation, fading and errors from multipath, and signal loss from cross-polarization.
- Differentiate between the characteristics of line-of-sight propagation (VHF/UHF) and ionospheric skywave propagation (HF).
Quick Checks
- What is the formula to calculate approximate wavelength in meters from frequency in MHz?
- What property of a radio wave defines its polarization?
- Which region of the atmosphere can reflect HF radio waves?
- How does vegetation affect UHF and microwave signals?
Questions in This Topic
Choose Practice ModeT3A01Why do VHF signal strengths sometimes vary greatly when the antenna is moved only a few feet?T3A02How does vegetation affect UHF and microwave signals?T3A03What antenna polarization is normally used for long-distance CW and SSB contacts on the VHF and UHF bands?T3A04What is the effect of antenna cross-polarization over a line-of-sight VHF or UHF path?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 reflect HF radio waves?T3A12What effect does fog or rain have on 10-meter and 6-meter band signals?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?T3B12Which of these frequencies travels at the highest velocity 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 one 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?
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