It’s Time To Think About Your Grounding.
Spring and summer thunderstorms are just
around the corner and it’s time to think about your amateur radio equipment
grounding. I know that everyone and every communication company have their own
ideas and guidelines on how to ground communication equipment. Let me give you
just a little background on why I can speak about this topic. I am the Subject
Matter Expert for the company I work for from
What I am going to speak about here are working and proven concepts not theory. I will keep this topic at a high level overview. I want you to always remember that grounding is a two-way street and most damage to equipment comes from the outside environment discharges coming back into the inside of your house or “shack” as a result of ground loops. Never used solder to make ground dissipation connections as the solder will vaporize during a high voltage static discharge rendering your path to ground useless. Use mechanical type crimps or cad welds.
The first thing I want to make perfectly
clear is that I do not want you to confuse The National Electric Code, with the
National Electric Safety Code. The ONLY accepted code that is used in the State
What is your ground configuration? Grounding your “shack” is usually done by hooking up numerous conductors and then those conductors are taken to some house ground or ground rod. Take a moment and review your grounds in your “shack” and how they are hooked up and draw them on a piece of paper. While you are at it see if your grounds require a little maintenance. A loose ground connection is a bad ground connection.
There are typically two types of ground schemes, integrated and single point. An integrated ground is where all your equipment is hooked together, or daisy chained to your ground rod, bar or house ground. This is really not a good idea because you will probably have ground loops in this configuration. A single-point ground is where you will have a single ground wire from every piece of equipment that goes to your ground bar or ground rod. The single-point approach uses more wire and can become quite cluttered, but is more effective for many reasons and reduces the possibility of any ground loops. When installing grounding conductors do not install ground conductors in metallic conduit, and do not use any metal objects to support grounding conductors that would totally encircle the grounding conductor. Why? You just installed a choke around the grounding conductor and it will not pass a discharge.
Ground loops are the single biggest killer of equipment. Ground loops will also cause other problems in your “shack.” If you have problems with RF getting into your audio when you are operating your radio equipment, start looking for ground loops. RF travels on the surface of ground conductors not through them as you would think. Ground loops also provide another discharge path for lightning. How do you protect your equipment from lightning? I bet you disconnect your coaxes but do you unplug every piece of equipment from the AC outlets? If you do not, then you expose your equipment to possible ground loops. Huh? Well if your gear is plugged into an AC outlet, the equipment is connected to the power company ground and you may have a grounding conductor connected to your radio chassis ground also. Sure they might be the same ground as seen on your ohm meter but it has two different physical connections or loops. Oh, by the way did you check your antenna rotor cables?
The National Electric Code requires that any ground rod that is installed around your “shack” or home that is being served with a power company meter base is required to be connected to the power company ground. So why go to the trouble to build your own ground system? The last thing you want to do is to build a ground system that is better than the power company. The power company has a 25 ohms or less to ground resistance requirement, so if your nice ground system you built for your “shack” is 24.95 ohms or less then you will be the new discharge and AC current gateway for your house. The N.E.C. added this safety requirement in 2002 for connecting other ground rods or systems to the serving power company ground. Did you know that the N.E.C. has a requirement that all coax antenna cables that enter a building must be grounded or protected within the first ten feet after they pass through the wall? A comment about the N.E.C. phrase “Conditioned for Lightning.” What in the world does that mean? What the N.E.C. is trying to tell you is that any exposed metallic objects that could be struck by lightning, should be taken directly to the power company meter base or the ground rod directly under the meter base outside your house. The most important item to note here is that keep all of your outside ground connections outside, and all your internal ground connections inside. The only place where these two grounds should meet is at the electric company’s meter base or the ground rod directly under the meter base.
Here is a list of equipment connections that you may want to review in your shack to see if they create a ground loop: radios of all types (yes scanners too.), linear amplifiers, coax switch boxes, rotor cables, coaxes, coax lightning protectors, all metallic objects that come in contact with a bare basement concrete floor, phone lines, security systems, security cameras, intercom systems, cordless phones, computers, printers, tnc’s, modems, cable TV, satellite dish, external outside TV antenna’s, wired weather stations and wireless routers. Remember that grounds should be functional and should not win any awards for neatness. Use sweeping bends in your grounding conductors not 90 degree right angle bends.