Antenna Theory and Design Flashcards
7 cards from real HAM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Antenna Theory and Design flashcards as text
What is mutual coupling between antenna elements in an array?
Answer: The electromagnetic interaction between antenna elements that affects their impedance and current distribution
Mutual coupling is the electromagnetic interaction between nearby antenna elements that changes their individual impedances and current distributions from the isolated element case.
What is a beverage antenna and what is it primarily used for?
Answer: A long terminated wire antenna used for low-angle HF reception
A Beverage antenna is a long (one to several wavelengths) wire terminated in its characteristic impedance, used for low-angle receiving on HF bands with excellent directivity.
What is the significance of the E-plane and H-plane in antenna radiation pattern descriptions?
Answer: E-plane contains the electric field vector and H-plane contains the magnetic field vector in the direction of maximum radiation
The E-plane is the plane containing the electric field vector and the direction of maximum radiation, while the H-plane contains the magnetic field vector and maximum radiation direction.
What is the purpose of stacking two identical Yagi antennas vertically?
Answer: To increase gain by reducing the elevation beamwidth
Stacking Yagis vertically increases gain (about 3 dB ideally) by narrowing the elevation (vertical) beamwidth while maintaining the horizontal pattern.
What is an isotropic radiator and why is it used as a reference?
Answer: A theoretical antenna that radiates equally in all directions, used as a universal gain reference
An isotropic radiator is a theoretical point source that radiates equally in all directions (4π steradians), used as a universal reference for expressing antenna gain in dBi.
What is the effect of ground conductivity and permittivity on the radiation pattern of a low-frequency vertical antenna?
Answer: High-conductivity ground improves low-angle radiation efficiency and lowers the angle of maximum radiation
High-conductivity ground acts as a better reflector, improving low-angle radiation efficiency and pushing the angle of maximum radiation closer to the horizon, which benefits DX communication.
What is the term for the ratio of the maximum radiation intensity of an antenna to the average radiation intensity over all directions?
Answer: Directivity
Directivity is the ratio of maximum radiation intensity to the average intensity over all directions, and equals gain for a lossless antenna.