Why Antennas Have Ground Plane?

[ab cd]

A Simple Experiment to Demonstrate How Ground Plane Radials Affect the Performance of An Antenna

A 1/4 Wavelength Monopole Whip was tested under following conditions:
(1) Only Whip, no ground plane radials.
(2) Whip with horizontal ground plane radials.
(3) Whip with 45 degrees slanting ground plane radials.

The attached performance graphs show the importance & affect of ground plane radials.

Image 1 of 5
Device Under Test: 1/4 Wavelength Monopole, without & with radials

Image 2 of 5
Three Test Setups

Images 3, 4, & 5 of 5
Performance Graphs

 

[ab cd]

The Construction Details of the Antenna Under Test

All the 4 radials were inserted between the outer PVC jacket and the braid of the coax. The zip ties were used to secure the radials in position, as these have a tendency to move and change 90 degree angle with each other.

After completion, I checked the continuity between the body of F-connector at other end of coax, and each of 4 radials by a multitester. All 4 were found electrically continuous, as the multitester beeped on each radial.

The radials were inserted in the same way as a center wires of a Coco are inserted between the PVC jacket and braid of adjacent elements.

Here is a larger size photo of the monopole with radials inserted and zip-tied.