Practical takeaway
Directional arrays shape radiation by controlling relative current and phase in multiple elements. Gain comes from concentrating energy, not from creating power.
G9C · General question group
Directional Antennas
Directional arrays shape radiation by controlling relative current and phase in multiple elements. Gain comes from concentrating energy, not from creating power.
General exam focus
The explanation below teaches the ideas behind G9C while keeping the important terms recognizable. The Quiz Me button uses the current question-pool wording for this group.
1. Yagis use a driven element plus parasitic elements
A Yagi typically has one driven element, one reflector, and one or more directors. Element length and spacing create currents that reinforce radiation in the desired direction and reduce it in others.
2. Gain, front-to-back ratio, and beamwidth are different
Gain describes concentration compared with a reference; front-to-back ratio compares forward and rear response; beamwidth describes the angular width of the main lobe.
3. Stacking and phasing reshape the pattern
Two or more antennas can be combined with controlled spacing and feed phase to increase gain or steer/null the pattern. Feed-line lengths can become part of the phasing network.
G9C checklist
- A Yagi uses a driven element with reflector/director parasitic elements.
- Gain, front-to-back ratio, and beamwidth describe different pattern properties.
- Directional gain redistributes radiated energy.
- Spacing and phasing can combine antennas into an array.
Exam scope: NCVEC 2023-2027 General Class (Element 3), effective July 1, 2023 through June 30, 2027, with February 4, 2026 sixth errata. The current NCVEC pool is the exam authority; explanatory prose here is SPARKA teaching material. NCVEC pool