Grounding outdoor antennas

(Ordering materials needed for Grounding are at bottom of page)

For TVs, the main benefit of grounding is lightning protection.  Lightning is a powerful radio wave generator and any elevated wire is an antenna for it.  A lightning strike in your neighborhood can generate hundreds of volts, even thousands, on the coaxial line.  These voltages can damage your equipment.

To reduce these voltages the antenna cable should have a grounding block at the point where it enters the house, and that grounding block should be wired to a ground rod driven into the ground as close as possible to the grounding block.  An effective ground rod is one driven deep enough to reach into moist soil.

The ground rod should also connect to the mast via a heavy wire. Ground wires should be as short and straight as possible. Turns should be curves with a 6-inch radius. Ground wires do not need insulation.

Another advantage:  Appliance RF noise can travel up the outside of the coaxial cable to the antenna, and then back down on the inside to interfere with reception.  The grounding method described above will often eliminate that.

 The grounding method described above conforms fully to Channel Master recommendations. It does not fully conform to NFPA recommendations.

The NEC requirement

The National Electrical Codes (document NFPA 70) requires another wire be added to the grounding described above.

Outdoor Antenna Grounding

This 6-gauge wire, shown in red, connects the new ground rod to the breaker box (typically).  This wire will help absorb the lower frequency components of a direct strike.  If this seems like too much work for too little benefit, don’t be discouraged from at least installing the ground rod.  But if your antenna is situated where a direct strike is likely then installing this wire is strongly advised.  The wire should run close to the ground so that side flashes will likely arc to the ground.  It is OK to run this wire around the exterior of the building.  In this case keeping the wire 6” to 12” above ground is best.  The length of this wire is less important, but turns should still be curves of large radius.  (4-gauge aluminum can be used for this wire, but the rules forbid bare aluminum within 18 inches of the ground outdoors.)

 Some additional NEC rules

1. Do not attach an antenna to the power line service entrance power mast.  Outside the building, the antenna coaxial and grounding wires shall not come closer than:
1. 2 feet from exterior power lines of 250 Volts or less.
2. 10 feet from exterior power lines of greater than 250 Volts.
3. 1 foot from underground power lines.
4. 6 feet from lightning rod wires.

 (Although these are safety rules, they also reduce the pickup of appliance noise.)

2. If the antenna mast or wires come within 5 feet of a swimming pool, they must be bonded to the pool’s bonding grid.
3. Grounding wires and grounding blocks are permitted to be interior to the building.  (An interior ground rod might be in soil too dry to conduct much.)
4. Grounding connections must be constructed so that they will not come loose or corrode away.  (Any connection joining two different kinds of metal will corrode very rapidly if the connection can get wet.)
5. An interior cold water pipe is acceptable as a ground rod if the connection point is within 5 feet of where the pipe enters the ground.  (You must verify that the underground water line is not plastic.)
6. Indoor antennas (including attic antennas) are not generally susceptible to direct strikes.  In such cases a grounding block is not required by the rules, but is probably a good idea when the cable is longer than 30 feet.
7. There is nothing that you can do to guarantee that your electronics will survive a direct strike.  If you have any uncertainty about a safety issue or feel you are not competent with this portion of your antenna install, seek the advice of a registered electrician. Digital Antennas will not be held responsible for the accuracy of the above mentioned. Please consult your electrician for any local codes (if any) you may fall under.