Standing on Solid Ground
Welcome to Tech Talk, Pico Macom's series of technical notes, featuring useful information and equipment tips. This installment of Tech Talk discusses Pico Macom's line of quality grounding accessories.
Quality Ground
In this installment we will look at some of the reasons why it is important to ground an antenna system and the coaxial transmission cable. However, we will not go into the National Electrical Code or local electrical code requirements, since these can differ among states and municipalities.
The Antenna
In the antenna system (transmit/receive), effectively grounding the system serves two vital functions. The first is that bonding the antenna with earth ground allows the signal to be broadcast or received more effectively by creating a ground plane. This is similar to the FM radio antenna mounted on the body of an automobile or an amateur radio system. The second function is to provide a path to ground in case of lightning strike. Typically, an antenna extends beyond the highest point of a structure, making it susceptible to lightning strikes.
Transmmission Line
The coaxial cable used to transport the signal from the antenna should be grounded to provide another electrical path to ground. This is primarily to ensure that the consumer equipment in the home isn't damaged by any electrical current that gets induced into the shielding of the cable. In the case of a SMATV or CATV system, the grounding also provides additional protection against signal ingress/egress issues.
Consumer Equipment
The equipment in the customer's home can easily be damaged by an unstable power source. It is advisable to use the third-prong ground of an electric outlet when available. Never cut the third prong from a power cord. If the outlet doesn't accept a third prong, buy an adaptor at a local hardware store.
Grounding Application
Grounding the system is made simple with Pico Macom products. At the antenna, connection to the mast using an A-280 galvanized copper grounding strap will provide an effective connection.
- Clean the area with steel wool or a wire brush to ensure that there is a clean metal surface.
- Wrap the A-280 clamp around the mast and insert the peg into the hole on the strap that provides the tightest connection.
- Tighten the bolt on the A-280 until there is a snug connection.
- Wrap the ground wire around the bolt and tighten the nut down onto the ground wire.
- Protect the connection against corrosion by applying conductive grease (the same type used on car battery terminals) or wrapping electrical tape around the entire A-280 strap, ensuring that there is no path for water migration.
- Attach the ground wire and coaxial cable to the mast using CT-815BK self-locking tie wraps about every three feet down the mast. For added protection cut off the excess of the tie wrap and cover the tie wrap with electrical tape.
The coaxial cable is easily connected by placement of an inline grounding block. Select the grounding block that suits the requirements of your application:
- If a single coaxial cable is used and the signal is from an antenna, the GRB-1 would be suitable.
- For a single coaxial cable in a CATV application, the GRB-1HRL provides the performance needed.
- If two coaxial cables are used, the GRB-2HRL would be the answer.
- If two coax cables are used and there is a need to ground splitters or an amplifier, the GRB-2HRL/3G3 would provide the performance and three ground connections.
Where the ground connection is to be made, cut the coaxial cable (remove power if using a preamplifier) and place F connectors on the ends. Attach the male F connectors to the GRB-series ground block. Slip the ground wire into the hole under the ground bolt. Tighten the ground bolt until there is a snug connection to the ground wire.
Ground wires should be run to an effective ground. This could be an A-21-4 ground rod secured with an A-3/8 acorn ground rod clamp, or an A-286 copper ground strap connected to a cold water pipe. To connect to the grounding rod, slide the A-3/8 clamp over the end of the rod. Pound the rod into the ground, leaving two inches above the ground. Place the ground wire between the rod and clamp and tighten the bolt on the clamp securely. Pound the rod the rest of the way into the ground until the top is below or flush with the top of the soil. It is a good idea to connect all grounds together whenever possible.
