The Basic lessons · Feedlines and antenna systems · B-006-012

Dipoles, Lengths, and Multi-Band Antennas

Learn how to calculate the physical length of a dipole antenna for any frequency and understand its unique donut-shaped radiation pattern. Discover the trade-offs of using traps and end-fed designs to operate on multiple bands with a single antenna.

This lesson is part of SignalPrep Pro. The subsection's 9 exam questions are free to practise: practise B-006-012.

What this subsection asks

• If you made a half-wavelength dipole antenna for 28.150 MHz, approximately how long would it be?
• What is one disadvantage of a random wire antenna?
• What is the three-dimensional radiation pattern of a half-wavelength dipole in free space?
• What is the impedance at the feed point of a half-wave dipole in free space?
• Ignoring ground effects, what is the radiation pattern of a horizontal half-wave dipole installed with the ends pointing North/South?
• What is a major advantage of an end-fed half-wave antenna (EFHW)?
• What is a disadvantage of using an antenna equipped with traps?
• What is an advantage of using a trap antenna?
• If you were to cut a half-wave dipole for 3.75 MHz, what would be its approximate length?