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 impedance of a typical half-wave dipole antenna in free space?
Answer: 73 ohms
A half-wave dipole in free space has a feed-point impedance of approximately 73 ohms.
What happens to the SWR on a feedline if the antenna is perfectly matched to the line's characteristic impedance?
Answer: SWR equals 1:1
A perfect impedance match results in an SWR of 1:1, meaning all power is transferred to the antenna with no reflections.
What is the main disadvantage of using a very long coaxial feedline run at UHF frequencies?
Answer: Significantly increased signal loss
Coaxial cable loss increases with frequency, so long runs at UHF can lose a substantial portion of your transmit power.
Which type of antenna connector is most commonly used for handheld VHF/UHF transceivers?
Answer: SMA
SMA connectors are standard on most modern handheld (HT) transceivers due to their small size.
What is the term for the ratio of the maximum to minimum voltage along a transmission line?
Answer: Voltage Standing Wave Ratio (VSWR)
Voltage Standing Wave Ratio (VSWR) specifically measures the ratio of maximum to minimum voltage amplitude along the feedline.
A Yagi antenna's gain is primarily achieved by:
Answer: Focusing radiation in one direction using directors and a reflector
A Yagi uses parasitic elements (directors in front, reflector behind) to concentrate radiation in the forward direction.
What is an antenna tuner (also called an antenna coupler) used for?
Answer: To match the transceiver's output impedance to the feedline and antenna system
An antenna tuner transforms the antenna system impedance to match the 50-ohm output of the transceiver, maximizing power transfer.