Ham Radio Technician Test Antennas & Feedlines 2

Question 1

What is the approximate length of a quarter-wave vertical antenna for the 2-meter band (146 MHz)?

Accepted Answer

19 inches

Answer

A quarter-wave vertical at 146 MHz is approximately 19 inches (about 48 cm).

Question 2

Which feedline type has the lowest loss per unit length at VHF frequencies?

Accepted Answer

Open-wire ladder line

Answer

Open-wire ladder line has very low loss at VHF because of its air dielectric and wide conductor spacing.

Question 3

What does a balun do in an antenna system?

Accepted Answer

It matches balanced to unbalanced transmission lines

Answer

A balun (BALanced-UNbalanced) transitions between balanced antenna elements and unbalanced coax feedline.

Question 4

What is the radiation pattern of a vertical quarter-wave antenna over a perfect ground plane?

Accepted Answer

Omnidirectional in the horizontal plane

Answer

A vertical quarter-wave antenna radiates equally in all horizontal directions, making it omnidirectional in azimuth.

Question 5

What is the effect of increasing coaxial cable diameter on signal loss?

Accepted Answer

Loss decreases

Answer

Larger-diameter coax has lower loss because of reduced resistance and better power-handling capability.

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