Question T9A12
From subelement T9 - T9A
What is an advantage of a 5/8 wavelength whip antenna for VHF or UHF mobile service?
Why is this correct?
A 5/8-wavelength whip has more gain than a 1/4-wavelength antenna by concentrating more signal toward the horizon instead of radiating it up into the sky. This redistribution of RF energy creates apparent gain for mobile operations on flat terrain. Choice B is wrong because high-angle radiation would be a disadvantage for mobile work. Choice C is incorrect as the antenna design doesn't eliminate multipath distortion. Choice D overstates the gain—it's not a 10:1 power increase.
Memory tip
When comparing mobile antennas, longer typically means more horizontal gain. The 5/8-wave design trades some upward radiation for better horizon coverage, making it ideal for car-to-repeater communications on level ground where the repeater is at your elevation or below.
Learn more
In mobile operations, 5/8-wave antennas excel on flat terrain but may underperform in mountainous areas where repeaters are located above you. The increased horizontal gain comes at the cost of reduced high-angle radiation. For canyon or hilly operations where you need to reach elevated repeaters, a standard 1/4-wave antenna often provides better frequency privileges coverage despite its lower theoretical gain specification.
Think about it
Why do you think a 5/8-wave antenna might actually perform worse than a 1/4-wave antenna when trying to reach a mountaintop repeater from a valley?