Antennas & Feedlines Flashcards
7 cards from real Ham Radio Technician Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Antennas & Feedlines flashcards as text
What is the approximate length of a quarter-wave vertical antenna for the 2-meter band (146 MHz)?
Answer: 19 inches
A quarter-wave vertical at 146 MHz is approximately 19 inches (about 48 cm).
Which feedline type has the lowest loss per unit length at VHF frequencies?
Answer: Open-wire ladder line
Open-wire ladder line has very low loss at VHF because of its air dielectric and wide conductor spacing.
What does a balun do in an antenna system?
Answer: It matches balanced to unbalanced transmission lines
A balun (BALanced-UNbalanced) transitions between balanced antenna elements and unbalanced coax feedline.
What is the radiation pattern of a vertical quarter-wave antenna over a perfect ground plane?
Answer: Omnidirectional in the horizontal plane
A vertical quarter-wave antenna radiates equally in all horizontal directions, making it omnidirectional in azimuth.
What is the effect of increasing coaxial cable diameter on signal loss?
Answer: Loss decreases
Larger-diameter coax has lower loss because of reduced resistance and better power-handling capability.
A 5/8-wave vertical antenna is often preferred over a quarter-wave vertical for VHF because it has:
Answer: A lower radiation angle and slight gain over a quarter-wave
The 5/8-wave vertical has a lower radiation angle than the quarter-wave, providing a few dB of gain toward the horizon.
What is the purpose of a ground plane on a vertical antenna?
Answer: It acts as the other half of the antenna and provides a return path for RF current
The ground plane (radials) completes the antenna system by providing a low-impedance RF return path, simulating actual earth ground.