In case you haven’t noticed, I have been writing less lately. This is because the day job has been more demanding and we’ve been trying to get some things finished around the house. However, it’s now the weekend so I have a little time. My goal is to get some things caught up so I can write more regularly again.
Today was a functional ham radio day. I installed a new ground system with Adam’s help (thanks, Adam, and I mean big time!) It used to be that grounding was a concept that was not limited to electricians and radio aficionados. It was something that was routine high school physics and played into many handyman projects around the house.
Scientists theorized that the earth is large enough and has sufficient mass that it would not be possible for any electrical charge to be large enough to change the earth’s overall charge. People could pump all the electrons possible into the earth and it would make no difference. As such, the concept of an earth ground provided a useful and practical way to connect electrical devices. It takes a complete circuit for an electrical charge to flow. In a flashlight, for example, when the switch is closed the electrons flow from the battery, through the switch and the light bulb and then back to the battery. One end of the battery is + (positive) and the other – (negative). When there is a difference in the level (potential) between the + and the – electrons flow. (Think of walking through the house in winter; your shoes and the carpet create a charge on you so that when you touch a door knob the electrons flow and you get a “shock”.)
When the telegraph was invented, it was possible to use a single wire to connect the telegraph stations. The other half of the circuit was achieved by using the earth ground. The electric current flowed from the battery to the telegraph stations and then back to the battery through the earth ground.
In radio, ground systems play two important roles. The first is relatively straight forward; antennas are metal structures that are erected as high as possible. This is not the optimal location during a thunderstorm so the ground is a means of protecting the antenna and the radio from lightning. There is no protection from a direct lightning strike, but by connecting the antenna to a suitable ground, any static charge will hopefully be drained into the earth thereby reducing the possibility of attracting lightning. If the antenna is neutral in relation to the storm, the lightning should be attracted to some other location with a different charge than the cloud. This lightning protection ground can be achieved by driving an 8 or 10 foot conductive rod into the earth.
The second role of the ground is going to require some oversimplification. When a radio transmits a signal, if everything is adjusted properly, the signal exits the antenna. Even with radio there is still the need for a circuit; the antenna is one half, the ground the other. This is a radio frequency (RF) ground and is a bit more complicated. While the ground rod is important, when dealing with RF a ground system is needed. As of today my ground system consists of three ground rods spaced about 20 feet apart with heavy gauge copper wire buried just under the surface connecting them.
Heavy gauge wire tends to bend when you don’t want it and not bend when you do. This means that just after you get it buried, a segment pops up, so building a ground system takes longer than you expect. Likewise, 10 foot copper clad grounding rods take effort to sink into the ground. Bottom line is that Adam helped me get it built and it’s functioning well. When I tested it I was able to make contacts with better results and less noise than in the past.
Oh, and in the process, I got to sneak a physics lesson in on my readers.