Whether it’s professional transmitting equipment or local ham radio, grounding is the key to a safe system
If you install satellite dish antennas, you must follow the requirements of Art. 810. It provides the requirements for television and radio receiving equipment, like the aforementioned satellite antenna and the following receiving equipment:
VHF/UHF antennas, which receive local television signals. These antennas can have a rotor motor for turning the antenna from inside the building.
Antennas for AM/FM radios. These radios have built-in antennas, but some remote areas use antennas for improving reception.
Amateur radio transmitting and receiving equipment, which is also known as ham radio. Even though it's a noncommercial (amateur) form of communication, you still need a license to be a ham radio operator.
Keep in mind that Art. 810 addresses only those issues specific to this kind of equipment. You still must supply power per the requirements of Chapters 1 through 4. Wiring for audio signal processing, amplification, and reproduction equipment must comply with Art. 640. If you use coaxial cables to connect antennas to equipment, you must comply with Art. 820 (Fig. 1).
The wiring for a community television antenna must comply with this article, and the distribution coaxial wiring must comply with Art. 820. Don't confuse a community television antenna (Art. 810) with community antenna television (CATV) [Art. 820]. A community TV antenna can be used for multiple units in apartments, condominiums, motels, or hotels. On the other hand, CATV is utility-supplied cable TV.
Part II of Art. 810 addresses receiving equipment, while Part III addresses amateur transmitting and receiving equipment. Let's look at Part II first.
Receiving equipment. You must securely support outdoor antennas and lead-in conductors. Secure the lead-in conductors to the antenna as noted in 810.12. Don't attach lead-in conductors to the electric service mast.
Avoid contact with conductors of other systems. The NEC Handbook says, “One of the leading causes of electrical shock and electrocution, according to statistical reports, is the accidental contact of radio, television, and amateur radio transmitting and receiving antennas and equipment with light or power conductors. Extreme caution should therefore be exercised during this type of installation, and periodic visual inspections should be conducted thereafter.”
Outdoor antennas and lead-in conductors must not cross over open conductors of electric light or power circuits. Keep them well away from all such circuits to avoid the possibility of accidental contact. If you can't avoid proximity to open electric light or power service conductors of less than 250V between conductors, provide a clearance of at least 2 feet between them. Where practicable, install antenna conductors so they don't cross under open electric light or power conductors.
Per the requirements of 810.14, make any splices mechanically secure with approved splicing devices or by other means that won't weaken the conductors.
When you size the outdoor antenna conductors for receiving stations, use Table 810.16(A). Outdoor antennas must be strong enough to withstand ice and wind loading conditions and they must be located well away from power lines to avoid accidental contact.
The three sets of clearances in 810.18 are outdoors, indoors, and enclosures:
Separate underground antenna lead-in conductors at least 12 inches from power or Class 1 conductors. Separation isn't required if Class 1 conductors or power conductors are contained in a raceway. There are no burial depth requirements for antenna lead-in wires.
Separate indoor antenna and lead-in conductors by at least 2 inches from conductors of any electric light, power, or Class 1 circuit conductors. However, this doesn't apply to installations in which the lead-in conductors or the electric light, power, or Class 1 circuit conductors are installed in a raceway, metallic or nonmetallic sheath or UF cable.
Indoor antenna lead-in conductors can be located in the same enclosure with conductors of other wiring systems where separated by an effective, permanently installed barrier.
You must provide each conductor of a lead-in from an outdoor antenna with a listed antenna discharge unit (ground block) (810.20). If you put a discharge unit inside the building, place it nearest the point of entrance — but not near combustible material. You can also place it outside the building, thus eliminating any potential problems stemming from location inside the building.
Grounding the receiving equipment is critical. If the mast isn't properly grounded, induced voltage spikes from lightning strikes can destroy the low-noise block (LNB). They can also destroy the DC rotor motors that control the positioning of satellite dishes. If the lead-in from an outdoor antenna isn't properly grounded, induced voltage spikes from lightning strikes can destroy the receiver.
Ground the antenna discharge unit (Fig. 2 above), the antenna mast, and antenna discharge unit (ground block) per 810.21 (Fig. 3). If an antenna mast is within 5 ft of an outdoor swimming pool, bond it to the pool common bonding grid [680.26(B)(5)].
Grounding conductors must be copper or another corrosion-resistant conductive material (stranded or solid), but insulation isn't required. You can run the grounding conductors inside or outside the building. If the grounding conductor is made of copper, it must not be smaller than 10 AWG.
You must securely fasten these conductors in place and provide protection from physical damage as needed. Where the grounding conductor is installed in a metal raceway, bond each end of the raceway to the grounding conductor or the same terminal or electrode to which the grounding conductor is connected. Run the grounding conductor to the grounding electrode in as straight a line as practicable — this improves lightning protection. Lightning doesn't like to go around corners or through loops in the wire, which is why the grounding conductor needs to run as straight as practicable.
If the building or structure has no grounding means, terminate the grounding conductor to any of the individual grounding electrodes described in 250.52. Otherwise, connect the grounding conductor to the nearest accessible location of one of the following:
The building or structure grounding electrode system as covered in 250.50.
The grounded interior metal water-piping system, within 5 feet of its point of entrance to the building [250.52(A)(1)].
Accessible bonding means, such as 6 inches of 6 AWG copper conductor connected to the service equipment or raceway [250.94].
The metallic service raceway.
The service equipment enclosure.
The grounding electrode conductor or the grounding electrode conductor metal enclosures.
Bond the electrode for the radio and television equipment (if used) to the building's power grounding electrode system with a conductor not smaller than 6 AWG copper or equivalent (Fig. 4 below). The point of this is to prevent flashover between the electrodes by equalizing the potential with a bonding jumper.
Don't assume the earth can be your bonding jumper. That copper jumper's resistance will be negligible, while the earth will have a resistance of millions or billions of ohms, even on a wet day.
Correctly implementing the requirements of Art. 810 is fairly easy if you remember the three concepts it addresses. First, this is very low-voltage wiring — keep it away from power wiring. Second, secure the equipment away from power wiring to prevent the chance of accidental contact. These first two concepts are important because so many people have died from accidental contact between radio/television equipment and power wiring.
Third, bond all electrodes together and to the common power electrode. This prevents flashover. Electricity is trying to get back to the source, which is why usable electrical circuits are possible. If the path you provide is too high in resistance, electricity will find another — possibly lethal — way back to the source. When you need to safely install radio and television equipment, always go back to your own source: Art. 810.