Ham Radio General Class Practice Test

When the radials of a ground-plane antenna are changed from horizontal to downward-sloping, the feed-point impedance of the antenna tends to increase. This is primarily due to the change in the effective electrical length and the radiation pattern of the antenna.

Radials that are positioned downward increase the angle of radiation and can lead to a difference in how the antenna interacts with the ground. This altered geometry causes variations in the surface currents on the radials and can result in changes to the impedance seen at the feed-point.

Additionally, as the radials are inclined downward, the ground's return path and effective coupling can change, affecting the overall impedance. In essence, downward-sloping radials move the antenna's characteristics away from what is typical for horizontal radials, mostly depending on the specific design and environment, but generally leading to an increase in feed-point impedance.

This understanding of how radials affect feed-point impedance can be crucial when designing and troubleshooting antennas for optimal performance.