2. External grounds: a better place for lightning!

Lightning does not bypass tall trees, antenna masts, dipoles, or the roof and chimney of a house in favor of coming into the house or station first. It just doesn't happen. What does happen to stations that improperly bond or ground, is that lightning starts down trees, antennas, chimneys, etc., and then discovers ungrounded and / or unbonded electrically conductive equipment inside the station. It reaches this unbonded equipment two ways: from magnetic and capacitive coupling, and via the return-stroke current from ground.  

Case in point below:

Outside feedlines were disconnected near the base of a grounded tower and lay next each other on the grass. These open feedlines are still connected inside the station to ungrounded and unbonded equipment. One antenna accidentally remains fully connected but like the rest, has no shield-grounding or coax arrestor system.  All equipment is grounded only by virtue of being connected to AC power, and most is unplugged at the time. None of the equipment is common bonded. With the exception of the one connected antenna this time, the station in this condition had survived tower strikes in the past with minimal or no damage. Disconnecting antennas outside and unplugging AC power inside was the lightning protection plan.

A MAJOR strike occurs, exploding the one connected antenna and destroying the radio it is connected to.

In the station, violent flash-overs from radios to computers, even disconnected equipment occurs.  While some of this massive lightning energy is ruining equipment on it's way to and from the ground, most parts of the house wiring are being inductively charged to the point of damaging or destroying most things plugged into those circuits. It's a very destructive event, and some minor damages take months to be discovered.

It could have been worse, but not much.  One of the return-strokes shot rifle-caliber holes through unbonded equipment, induced EMI that tore up 12" holes in tile flooring where a lone test cable hung, and disintegrated 12vdc converters wherever they were plugged in. The operator had the misfortune to witness these events from inside the station. Thank God, he wasn't touching anything when it happened.

While this case was somewhat rare in it's severity, even the worst lightning possible can still be mitigated, and most lightning damage can be avoided completely.

Now what if your rooftop antennas, tower, and all equipment are properly grounded and bonded?

Lightning will direct most of it's energy straight to ground outside the station, with minimal if any damage to the antennas themselves. Can some lightning energy come inside via the coax feedlines?

Yes.  But it will be less than what travels a lower impedance path of the antenna's own common ground rods. Shield grounding the coax at the tower top, tower base, and entrance to the station is a must. Finally, the coax feedlines require either Lightning Arrestors or they must be disconnected and shorted to common ground. Not all coax lightning arrestors are created equal. There is one type made by Industrial Communication Engineering (ICE) that uses a multi-attack system which they claim has never been defeated by lightning. Still, the failure of other manufacturer's lightning arrestors are often claimed when the real cause of lightning damage was due to improper or nonexistent bonding, poor grounding, failure to shield-ground, and/or lack of proper surge protection. Even a single-mode gas tube arrestor can do the job it is designed for just fine. It can't work miracles, and failure to shield-ground the coax before the arrestor will destroy the arrestor.

Commercial-grade surge suppression is still required for the station wiring, or in it's absence, all equipment must be unplugged. All this information, taken as a whole, provides solid protection.

I use rooftop masts for UHF/VHF-marine, and tree-supported horizontal wire antennas for HF-aeronautical. All of my rooftop antennas are bonded together and to ground rods with #2 solid copper wire. The antenna grounding is of course common-bonded to the station's ground system after those down conductors first connect to their own 8' ground rods.  All coax feedlines enter the station from underground, are shield- grounded and then protected by ICE lightning arrestors. These arrestors are mounted to the station Master Ground Bus, which is 4' above the first ground rods of the grounding system. While this provides protection from a direct strike, grounding, bonding and arrestors do not prevent induction of lightning energy on the home or station electrical wiring. Without surge protection at both the house service entrance and the local load-center or power-supplies*, you must disconnect the AC power supplies to all equipment in order to protect them from electro-magnetic induction and it's very destructive energy.

    * Polyphaser Corp and it's parent Transtector, as one example, makes devices to protect individual power supplies and whole-house circuits by TVSS (Transient Voltage Surge Suppression). Links to these companies and others are available at the end of this website.

3. Radio Frequency (RF) Ground Systems

Radio Frequency (RF) grounding is not related to lightning or electrical safety per se, except that if RF energy leaks onto the coax shielding because of poor tuning, high SWR in antenna systems, etc., there is both a safety issue and poor efficiency. More importantly, if the RF ground system is not bonded to the lightning protection system, the entire SPGS could be rendered useless. Serious damage could result.

RF ground systems and lightning ground systems must be bonded together, no exceptions. *

Some types of transmitting antennas require ground radials (buried copper wire paths in a 360-degree pattern) in order to effectively radiate. My antennas derive no benefit from RF radials so I do not use them. But all transmitting stations should have an RF Ground at the transmitter. This can be provided by the station AC ground wiring, but that has a lot of shortfalls. A good transmitter RF ground system should be integral and dual-purpose with the station grounding system.

As most stations provide, I installed an extremely low impedance RF Ground System. I took the further precaution of using multiple RF ground rods connected in close parallel circuits to each other. This prevents a high frequency phenomenon known as "1/4 wave resonance". Whenever an RF ground wire is 1/4 wavelength of the transmit antenna, the inductive resistance of that RF ground wire raises dramatically. In effect, it becomes no ground at all and has serious safety consequences. That must be avoided by transmitter to RF ground lengths shorter than 1/4 wavelength, and/or connecting two or more RF ground rods in parallel.

Whether a transmit station requires antenna ground radials, or just the transmitter RF ground system as mine does, the following always applies:

An RF ground system and lightning ground system must be bonded together, no exceptions. *

Make sure that any down conductors from roof lightning rods and masts reach their own ground rod first before bonding to the rest of the RF and station ground system. Down conductors will carry the direct energy of an entire lightning strike and you do not wish to share this with your station before it reaches ground!

Notice we did not dwell too much on ground rods. Don't push them through buried utilities, put at least one and preferably three for each down conductor (at least their sum-depths-apart in a "Y" pattern), and don't assume you are getting a "real good ground" unless you have it tested professionally.  The reason we don't spend more time on grounding here is two-fold: 1. Everyone knows that we must have ground rods (this wasn't intended for beginners to lightning protection) and 2. The bonding and surge protection are simply more important. That, I fear is grossly misunderstood, and it is perhaps the #1 reason why lightning is so destructive to so many well-intentioned people, who thought they were protected.

Here's why!
Next:   Inductance - Why grounding is Never Enough

    *    For marine applications, i.e.: sailing vessels desiring to isolate RF ground system for galvanic protection, reference Marine Grounding. Bonding not only still applies, it's absence is deadly!