What is a “ground plane?”

This one’s a bit confusing. First of all, we’re not talking about a grounded plane which is what happens when a 737 has engine trouble. That’s another whole thing.

A ground plane, at its simplest, is a large piece of metal, larger than the wavelength of the signals that pass through it. It’s sometimes connected to a ground wire or to the earth itself. It’s used for a number of different things.

Ground planes on antennas

In the case of a receiving antenna, a ground plane is mounted parallel to the earth that functions as a reflector and makes the antenna itself more useful. In this case the ground plane doesn’t need to be connected to anything in order to work.

You’ll find ground planes on base station antennas such as those on the roofs of hospitals or police stations. The frequencies used by those first responder radios tend to benefit from having a ground plane.

It’s also worth pointing out that in the case of the antenna, a ground plane doesn’t have anything to do with grounding. It’s not even connected to the ground wire. These antennas need to be grounded separately from the ground plane.

Ground planes in computer chips

In circuitry, a ground plane is a large metal area on a circuit board that serves as the negative terminal for a large number of electrical connections. In that case it generally does get connected to a ground wire through the case or other components, but that isn’t mandatory as long as the circuit is designed not to need a grounded connection.

Automated manufacturing uses ground planes to make things simpler. Circuit boards are very complex and tiny. Robots do most of the manufacturing. They have to. Humans could never work with such tiny parts. Using a ground plane makes it faster and easier. That also cuts down on costs and makes stuff affordable.

Ground planes in AV installations

In commercial applications, a ground plane is a large piece of metal that’s used as a backboard for connecting a lot of different components. That one piece of metal is bonded to the building’s ground system. As long as the components on it are making a metal-to-metal connection to that ground plane, then everything is properly grounded. It’s a lot easier than running individual ground wires from a whole bunch of individual components to a central grounding block and then to the building’s grounding system.

A ground plane does not have to be special, it just needs to be a big chunk of conductive metal that things connect to. In the case of commercial applications, you’re not dealing with broadcasting frequencies so the actual size doesn’t matter, as long as it’s big enough for the things you connect to it.

Grounding vs. Bonding

Technically, we use the term “grounding” for a direct connection to the earth. When you connect a copper wire to a post that’s driven into the ground, that’s grounding. Connecting to a water pipe is also grounding.

Bonding is when you connect to a system that is then connected to a ground… hopefully somewhere. If you take the same copper wire and connect it to the frame of your breaker box, that’s bonding. So, that’s where it gets confusing. Ground planes for AV installs are very rarely “grounded.” They’re almost always “bonded” unless they’re close enough to the outside to have their own ground wires. So why don’t they call them “bond planes?” I don’t know, other than that sounds like something 007 would use to escape Blofeld.

One perfect use of a ground plane is a satellite headend system. In a headend system, the multiswitches, splitters, and other small bits are all connected to a ground plane. Typically these things would have been mounted to plywood in many installs but using a metal ground plane instead is an easy way to make sure everything is properly bonded without spending a lot of time.

Get the grounding accessories you need from Solid Signal

No matter what kind of ground plane you need, you’ll find it at Solid Signal. Shop at Solid Signal for ground plane antennas or ground planes for circuits. We have tens of thousands of hard to find parts. Is this all just incredibly confusing? That’s what our tech experts are here for. Call 888-233-7563 to reach someone who really understands. We’re here for you during East Coast business hours. If it’s after hours, fill out the form below. We’ll get back to you, usually within one business day.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 10,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.