FAQs — What About Lightning?

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What About Lightning ?

Lightning is a serious problem in Florida. Whether you receive your TV signal from satellite, cable or off the air, you are vulnerable. With the proper precautions, you can make your installation relatively safe from a lightning strike.

Cable

For cable, you should have a lightning arrestor that is tied to a ground rod outside of your house, preferably to the same ground rod as the house wiring uses. Cable installers are trained in this procedure to meet code but it is prudent to trust but verify this critical ground installation.

Satellite

For satellite dishes, you should have a ground wire from the dish to a ground rod and have an inline arrestor which is tied to the same rod. Ideally the ground should be the same as the house wiring ground rod. The 8ft ground rod should be close to the dish and connected by low gauge copper wire. The wire and grounding clamps can be found at Lowes and Home Depot. If possible, use two 8' ground rods spaced about 10 feet apart. A conductive grease should be used on all connections to keep them from oxidizing.

Over The Air

For TV antennas, the rules are pretty much the same as for the satellite dish. Instead of running a separate wire from the antenna to the ground rod, you can tie the 8ft ground rod to the mast with low gauge wire. Be sure to clean the area where connections are made to the mast and ground rod. If possible, use two 8' ground rods spaced about 10 feet apart.  A conductive grease should be used on all connections to keep them from oxidizing.

Coax lightning suppressors are available at Radio Shack, Home Depot, Lowes and similar stores. If you need to install a ground rod, use an 8'ft rod, available at your nearest home supply store. Ground wires should be kept as short as possible and use a low gauge solid copper wire. The wire, ground rods and grounding clamps can be found at home supply stores such as  Lowes and Home Depot. A conductive grease should be used on all connections to keep them from oxidizing.

Never install an antenna near power lines, including those running to your house. Always plan enough space in case the mast and antenna should come tumbling down in a wind storm.

Antennas In The Attic

If you think you are safer putting your antenna in the attic, think again. 

Lightning has traveled through a few thousand feet of air (which is a good insulator), two inches of plywood and shingles are not going to make any difference. Roofing nails will add a direct path through the roof anyway.

In the attic, the antenna is grounded through your equipment. This is the path all the static charge (and potentially lightning) will flow. There is always static charge, even when there are no storms around. Because the path is through your equipment it is a relatively high resistance path. This also means your HDTV receiver is having to drain any charge build up on the antenna through the house wiring.

The attic antenna needs to be grounded the same way as an antenna mounted outside.

Stainless Steel Porcupines

Stainless steel porcupines, when added to a well grounded antenna system, are very effective at draining off the charge that build up around your antenna.  You should use around 3 (total) of them on the antenna mast. They can be purchase at Davis RF. The folks at Davis RF are very helpful if you call them and ask for advice. Remember, you have spent a lot of money on your home entertainment system, its worth as few extra bucks to make sure it doesn't become a boat anchor.

Porcupines will help protected about a 50 ft radius around the installation. For example if your satellite dish is near you TV antenna, your dish will also benefit. The dish still needs to be grounded (and share the same ground as your TV antenna).

Maintenance

It is best to coat all the connections with a conductive grease to minimize oxidation.  Remember to check the connections each year before summer and re-clean and re-grease as necessary.

Background Information

The key to lightning protection is to dissipate the charge before it builds up enough potential to ionize the air and form a strike. This requires a low resistance path to ground to dissipate it. Use low gauge wire and a couple of  8'ft ground rods with good connections to the mast and antenna. The addition of stainless steal wire porcupines is the best solution.  Be sure all connections are clean and have a conductive grease applied to keep the connections low resistance.

An inline coax arrestor will help with near hits but doesn't do much to dissipate any charge build up and nothing for a direct strike. These types of arrestor turn on when there is a there a high enough voltage built up, they then 'spark' the excess charge to ground. If the voltage from a hear hit is high enough, the arrestor will generally burn itself out and shortly afterward your equipment.  Its always best to avoid draining the charge through you coax.  Generally speaking, nothing survives a direct lightning strike. The most important aspect of a surge protector power strip is the equipment warranty. Save your receipt and warranty card.

Here's a link about lightning http://thunder.msfc.nasa.gov/primer/

Because of the way charges in sky, earth and ocean build up, the coast line is the worse place to be during a lightning storm. Lightning strikes are more prevalent on the coastline. Beach home owners should take as much precaution as possible.