US_TECH_2022_2026
Technician 2022-2026 - Antennas and feed lines
Antennas and feed lines groups the T9 section questions for focused review and easier weak-point tracking.
24
Questions
9
Sibling Topics
- Pool
- Technician 2022-2026
- Questions
- 24
- Topic
- Antennas and feed lines
- 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 fundamentals of antennas and feed lines in amateur radio, including antenna types, polarization, length calculations, coaxial cable characteristics, and basic SWR concepts.
High-Yield Checks
- Antenna length calculations: A 1/4 wave for 146 MHz is about 19 inches; a half-wave for 6 meters is about 112 inches.
- Antenna types and gain: Yagi offers the highest gain; beam antennas concentrate signals in one direction; dipoles radiate strongest broadside.
- Feed lines and connectors: Standard coax impedance is 50 ohms. Loss increases with frequency. Type N connectors are preferred above 400 MHz.
- SWR and tuners: Low SWR reduces signal loss. Tuners match impedance rather than altering physical length. Erratic SWR usually indicates a loose connection.
Trap Patterns
- Assuming a "UHF connector" (PL-259) is best for UHF frequencies. In reality, Type N is preferred for frequencies above 400 MHz.
- Confusing antenna "loading" with physical weight or wind resistance, when it actually means electrically lengthening the antenna using inductors.
- Believing antenna gain magically creates or amplifies power. Gain simply focuses the existing transmitter power in a specific direction.
Review Steps
- Memorize the frequently tested antenna lengths (19 inches and 112 inches) or master the wavelength-frequency conversion.
- Compare and memorize coaxial cables (e.g., RG-213 has lower loss than RG-58) and connectors (PL-259 vs. Type N frequency suitability).
- Understand basic SWR concepts, what causes erratic changes (like loose connections), and the benefits of low SWR (reduced loss).
Quick Checks
- What is the most common impedance of coaxial cables used in amateur radio?
- Which RF connector type is most suitable for frequencies above 400 MHz?
- In which direction does a half-wave dipole antenna radiate the strongest signal?
- What happens to the loss as the frequency of a signal in coaxial cable is increased?
Questions in This Topic
Choose Practice ModeT9A01What is a beam antenna?T9A02Which of the following describes a type of antenna loading?T9A03Which of the following describes a simple dipole oriented parallel to Earth's surface?T9A04What is a disadvantage of the short, flexible antenna supplied with most handheld radio transceivers, compared to a full-sized quarter-wave antenna?T9A05Which of the following increases the resonant frequency of a dipole antenna?T9A06Which of the following types of antenna offers the greatest gain?T9A07What is a disadvantage of using a handheld VHF transceiver with a flexible antenna inside a vehicle?T9A08What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?T9A09What is the approximate length, in inches, of a half-wavelength 6 meter dipole antenna?T9A10In which direction does a half-wave dipole antenna radiate the strongest signal?T9A11What is antenna gain?T9A12What is an advantage of a 5/8 wavelength whip antenna for VHF or UHF mobile service?T9B01What is a benefit of low SWR?T9B02What is the most common impedance of coaxial cables used in amateur radio?T9B03Why is coaxial cable the most common feed line for amateur radio antenna systems?T9B04What is the major function of an antenna tuner (antenna coupler)?T9B05What happens as the frequency of a signal in coaxial cable is increased?T9B06Which of the following RF connector types is most suitable for frequencies above 400 MHz?T9B07Which of the following is true of PL-259 type coax connectors?T9B08Which of the following is a source of loss in coaxial feed line?T9B09What can cause erratic changes in SWR?T9B10What is the electrical difference between RG-58 and RG-213 coaxial cable?T9B11Which of the following types of feed line has the lowest loss at VHF and UHF?T9B12What is standing wave ratio (SWR)?
More Topics
FCC rules, station licensing, and operator dutiesOperating procedures and emergency communicationsRadio wave propagationStation setup and equipment operationElectrical principles and mathElectronic components and circuitsPractical circuits, troubleshooting, and measurementsSignals, emissions, and modulationElectrical, RF, and mechanical safety