Ground
A ground is a fundamental part of a properly equipped station. Without a ground, you are at risk of damaging your equipment or worse, causing physical harm to people around the device as a radio station changes the way your inhouse electric circuit behaves in case of a lightning strike.
Main article: Wikipedia:Ground (electricity)
Information here is provided AS IS and in no way ensures your own safety. This site takes absolutely no responsibility for the actions taken after consulting this documentation. You are responsible for your own actions and should read other sources to make up your mind on the safe course of action here. See also Project:General_disclaimer.
Different types of grounds
The ARRL distinguishes between three different types of grounds:
- Satefy ground - to protect against defects in your transceiver that may leak energy even though it's power plug is grounded
- Lightning ground - to protect against lightning strikes on the antenna or the electricity supply
- RF ground - to protect against RF radiations coming back in the shack with unbalanced antennas
A safety ground (the outside ground lead of your transceiver, for example) can be connected to the electric supply ground of your house.
A lightning ground should not be connected to the electric supply ground, however. It should be connected to a separate, station ground. Lightning protection can be done through the installation of surge protectors, but it is still important to connect your station to a separate station ground.
A RF ground should not be connected to the electric supply ground either. This is because the electric supply ground is longer and will start behaving as an antenna if it is a quarter of the wavelength, or a multiple of a quarter wavelength, of the frequency you are operating with.
So unless you have absolutely no chance of being hit by lightning (ie. you have no antenna or you are inside a house, and even then: lightning can strike at power poles), you will need a station ground that is separated from the electric supply ground.
Also note that an RF ground may be necessary even if you have a balanced antenna system (with a balun for example), because equipment can fail and then RF is driven back to the shack.
Building a station ground
A proper station ground will be a ground that is not connected to the electric power supply and close enough to your station to not emit RF (if you need a RF ground).
Such a ground may be a metallic cold water pipe (not plastic, not hot water!) or better yet, a custom-made ground rod, connected through a gage 6 or smaller (gage, not size).
Cold water pipes
Cold water pipes can act as a ground rod in some places. Note that in some cases, the cold water pipe system is actually connected to the house power supply ground, the phone system, or the cabling system or whatnot... So unless you know that nothing else is connected to the cold water pipes, you should consider another solution. They should also be avoided if you are far away from the actual ground.
Ground rods
A ground rod is made of copper-clad or plain copper steel. It should generally be driven into the soil at least 10 feet (3.25m). It is best if a network of ground rods is laid out, and that all ground rods are connected together. Consult the lightning protection articles of the ARRL or w8ji's documentation to build such a setup.
Ground plates
A ground plate is also a valid ground. It's a plate of copper-clad steel or plain copper made of a 30cm per 30cm square, buried 45cm below the soil.
Binding the grouds
Safety, lightning or RF grounds need to be connected together or bound securely together, as close possible to the ground. This avoids ground loops which can cause hum or interference, and will ensure all points of the station ground will be at the same potential when a lightning strike occurs.
Connecting to the station ground
Now that you have a real secondary ground close by, you need to connect your station's equipment to it. This can be done with a braided copper strip (at least 14-gage) that runs through your station's rigs and serves as a tie point for the ground leads of all radio equipment within your shack. You can use the braid from spare RG-8/U coax if you have extra.
The station ground needs to be connected directly to the station ground built above, and that connexion must be as short as possible. If this is a RF ground, it will start behaving like an antenna if the distance to the station ground is a quarter of the wavelength, or an odd number multiple of the quarter wavelength, your station is operating at. This can cause severe burns, harmful interference and other havoc so it should be avoided at all cost.
It is therefore a challenge to connect your ground properly for anybody building a station on the second floor or similar higher ground.
Some have taken the approach of simply not creating a lightning ground in their shack and simply work with a safety ground, which can be an acceptable compromise in certain conditions. For example, marine, space or aerial stations can't have a proper ground at all. Another example is people in apartment buildings where they can't even deploy an antenna in the first place.
Final words on safety
The above is just a collection of advice found on various websites. It is not the conclusions of a professional electrician or the results of a scientific study. Do not put your life on the line and consult with a professional if you are unsure about this.
In general, you should avoid operating in a thunderstorm! Disconnect all equipment and leave the shack!
External links
- Good article about problems a ground protects from
- Canadian Amateur Radio Basic Qualification Study Guide - source for some of the specifications for the ground here
- Grounding Systems for Amateur Radio Stations - The Tech Bench Elmers Amateur Radio Society (KF6GDJ)
- ARRL grounding Q&A
- Excellent serie from the ARRL on how to completely ground a station safely
- Antennas and grounds in appartments (PDF)
- Controversial article trying to tone down the usual warnings about grounding
- Directory of ground resources at dxzone.com