Grounding and Lightning Protection

Few topics start more arguments at a club meeting than grounding. Part of the trouble is that hams use one word, “ground,” for three different jobs. Once you pull those jobs apart, most of the confusion goes away.

This article explains what each ground does, why they all need to be tied together, and the habits that protect you, your radios and your house. It is a starting point, not a wiring manual. Your electrical code and your local inspector have the final word.

Three Grounds, Three Jobs

The safety ground is the green or bare wire in your house wiring. If a hot wire touches a metal case, that ground carries the fault current back to the panel so the breaker trips instead of the case staying live. Your power supply gets it through the round pin on its plug.

The lightning ground has a much harder job. It must carry a huge, very fast surge into the earth outside, before that energy finds a path through your shack. Because the surge rises so quickly, the inductance of a long or bent wire matters as much as its resistance, so short, straight, heavy conductors work best.

The RF ground is only needed by antennas that use the earth or a counterpoise as half of the antenna, such as a quarter-wave vertical. Radials do that job, as Verticals and Radials explains. A dipole needs no RF ground at all, and RF in the shack is usually cured with a choke on the feed line, covered in Ferrites and Common-Mode Chokes.

Why Everything Must Be Bonded

When lightning strikes nearby, the earth near the strike can rise to a very high voltage compared with the earth a short distance away. If your radio’s coax is grounded to one rod and its power cord is grounded to another, that difference can appear right across your radio. The radio becomes the bridge between two grounds, and it loses.

Bonding means connecting all the grounds together with solid conductors so they rise and fall together. If everything in the shack goes up by the same amount at the same moment, little current flows through your equipment.

Hams do this with a single-point ground. Every cable that enters the shack, including coax, rotator cable, power, phone and network, passes through one entry panel at one place. That panel is bonded to the building’s grounding electrode system, ideally close to where the electrical service enters. Equipment inside the shack is then bonded to a ground bus with short, direct straps.

What the Electrical Code Says

Most of the US uses the National Electrical Code, published by NFPA, sometimes with local changes. Article 810, Radio and Television Equipment, covers receiving antennas and amateur stations. ARRL notes that NFPA lets you read the code online for free.

In plain words, Article 810 asks for these things:

• Outdoor masts and metal antenna supports must be grounded.
• Each lead-in from an outdoor antenna needs a listed antenna discharge unit, unless the code’s exceptions for grounded shields or grounded antennas apply.
• The antenna’s bonding conductor must connect to the building’s grounding system, and any separate ground rod you drive for the antenna must be bonded to the building’s power grounding electrode system.
• Antennas and lead-ins must keep a minimum clearance from power conductors.

The code also sets minimum wire sizes and approved connection methods, and the details change between editions. Follow the edition your area has adopted, plus any local rules. Outside the US, your national wiring code applies instead.

Bonding to the service ground often means working at the meter base or main panel. That work belongs to a licensed electrician, who can also install a whole-house surge protector at the panel. It is money well spent.

Surge Protectors and the Entry Panel

A coax surge protector, sometimes called a lightning arrestor, sits in the feed line where it enters the building. When a surge arrives, it shunts the energy from the center conductor to its own case. That only helps if the case is bolted to something that can carry the surge away.

• Mount every protector on a metal entry panel or bulkhead, with clean metal-to-metal contact.
• Bond that panel to the grounding system with a short, straight, heavy conductor. Avoid sharp bends and coils of extra wire.
• Use one protector per coax, rated for your frequency range and power level.
• Protect rotator, control and data lines at the same panel, not just the coax.

Plug-in surge strips help with small power-line spikes, but they are not lightning protection. The National Weather Service says plainly that typical surge protectors will not protect equipment from a lightning strike.

Towers and Masts

A tower is the tallest thing around, so expect it to take a strike sooner or later. The code requires metal masts and towers to be grounded, and the usual practice is ground rods at the base, bonded to the tower and connected to the house system by a buried conductor. Many builders also bond the coax shields to the tower at the top and the base, then again at the entry panel.

Grounding a tall tower is real engineering, so follow the tower maker’s instructions and get help from someone experienced. Never climb alone, always use proper fall protection, and never climb when storms are anywhere in the forecast. Place every tower and antenna so that if it falls, it cannot touch a power line.

What Not to Do

• A Separate Ground Rod. Driving a rod outside the shack window and leaving it unbonded is the classic mistake. It creates exactly the voltage difference that destroys radios, and it does not meet the code.
• Lifting the Safety Ground. Never cut off a ground pin or use a cheater plug to cure hum or RF. You remove the protection that trips the breaker.
• Long Wires to an Upstairs Shack. A long ground wire from a second-floor shack is a fine bonding conductor, but on HF it is not an RF ground. It can even act as part of the antenna.
• Trusting a Power Strip. A surge strip does not make up for missing bonding or a missing entry panel.

Storm Habits That Work

Bonding and protectors reduce damage from nearby strikes. Distance is the only thing that reliably beats a direct one, so build a simple routine and stick to it.

1. Watch the forecast. When storms are expected, act early.
2. Disconnect the coax and control cables at the entry panel, and move the loose ends well away from your equipment.
3. Unplug radios, power supplies and computers from the wall.
4. If the storm is already overhead, leave everything alone. The National Weather Service advises against unplugging equipment during a thunderstorm because of the risk of being struck.
5. When you travel, leave the station disconnected.

Once a year, walk your ground system and look for loose clamps, corrosion and wires a mower has nicked.