Antenna Ground Rod - Does it Help?

The Engineering Web

Amongst the many fantasies surrounding antenna theory one frequent statement heard is "My ground rod is just as good as a radial system."

Go to any book on antenna design and you will read ground rods do not offer much in the way of conductivity at RF frequencies.

The stated purpose of a ground rod is to dissipate lots of low frequency energy from lightning surges to the earth. It will also help dissipate static charge buildup if your antenna has a DC current path to ground.

So what is the truth?

During installation of my vertical antenna system I decided to check if the ground rod did anything measurable to the SWR and resistance of the antenna system. Covered elsewhere on this site, this vertical antenna will eventually have 60 radials about 33 feet long stapled to the ground around the antenna. For testing, I assembled an approximately 17 foot copper radiator. During my testing I progressively added more and more radials to see how they change the antenna characteristics; These details are covered elsewhere on this web site.

This test has 28 33 foot copper wire radials distributed evenly around the antenna base. An 8 foot ground rod is also installed at the antenna base. A wire has been soldered to the copper ground rod and can be attached or removed from the grounding plate with ease.

Using a MFJ-259 we get the following measurements:

Frequency without Ground Rod with Ground rod
SWR Resistance SWR Resistance
11,000 kHz 3+ 40 3+ 40
11,500 kHz 3.0 29 3+ 30
12,000 kHz 2.1 25 2.1 25
12,500 kHz 1.4 30 1.4 30
13,000 kHz 1.4 45 1.4 45
13,500 kHz 1.8 70 1.8 70
14,000 kHz 2.5 95 2.5 100
14,500 kHz 3.0 200 3.0 200
15,000 kHz 3+ 200 3+ 200
15,500 kHz 3+ 200 3+ 200

Not much difference.

If you already have a good ground level radial system adding a ground rod does little to nothing to your antenna's performance and efficiency. The radial system's ability to capacitively couple the coax shield return currents to ground via its large surface area easily overwhelms any contribution made by the ground rod.

However, a ground rod is still not a bad idea for coupling DC currents to Earth including static build-up (if your antenna has a DC shunt) and lightning energy.

Conclusion: Put in a ground rod, but not for RF reasons.


Other Articles

Other Resources