Ham Radio General Class Practice Test

What characteristic describes a log periodic antenna?

1. Length and spacing of the elements increases logarithmically from one end of the boom to the other

2. Impedance varies periodically as a function of frequency

3. Gain varies logarithmically as a function of frequency

4. SWR varies periodically as a function of boom length

The correct answer is: Length and spacing of the elements increases logarithmically from one end of the boom to the other

A log periodic antenna is characterized by the length and spacing of its elements increasing logarithmically from one end of the boom to the other. This design allows the antenna to cover a wide frequency range while maintaining a relatively uniform gain and radiation pattern across that range. The logarithmic increase in element length and spacing contributes to the antenna's ability to operate effectively over multiple frequencies. As one moves along the boom from one end to the other, the dimensions of the elements change in accordance with a logarithmic scale, leading to enhanced performance in terms of bandwidth and gain. This makes log periodic antennas particularly useful for applications needing wide frequency coverage, such as during certain ham radio operations. While impedance and gain do change with frequency in many cases, they do not do so in a strictly periodic or logarithmic manner as described in the other options. Understanding the unique design and characteristics of log periodic antennas helps in grasping how they function effectively in various radio communication scenarios.