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Grounding, So Misunderstood!
"Grounding" a
satellite system is not actually what we do. We actually are Most installers will tell you that your system will work fine without a ground. In truth, many systems will work reasonably well, without any noticeable effects, when the ground is absent. Unfortunately, even if you don't know the reasons that follow, your system should be grounded! It is the law! It is for safety AND function of your system. (And Dish Network will no longer allow the system to be installed without one, if they know about it.) My interest in grounding is related to the finer details of the proper functioning of the system, especially in the context of a high definition picture quality and HD satellite dishes, with their weaker satellite signals. Grounding is more important than ever.
Satellite systems are low voltage systems. The cables are energized from receiver to dish whenever the system is in use. ALL local building codes as well as the NEC® require that all grounds be "bonded" together. Here's why...
Just as water flows to the lowest point, electricity flows to the lowest potential, or the best ground. Your satellite receiver is connected to a 120 volt circuit. The hot side of the circuit is protected by a breaker, but the ground, or neutral lead has no such limiting device. In the receiver's power supply, the power transformer will have its center tap attached to neutral. The receivers cabinet will be connected to ground. They are then tied together at the service panel. Then the coaxial cable is attached to the receiver. If the ground used for the coaxial cable is a better ground with lower potential than the one used for electrical service, then the entire house's current will, at least partially, flow back through the receiver's electrical service ground lead. From there, current will flow to the receiver cabinet, through the coaxial cable's shield (the ground part of the wire), to the grounding block and then to ground. How much current that flows depends on the ground potential difference. Aside from the effects such current may have on the transformer and voltage regulator in the power supply, the potential danger to anyone touching the receiver is serious, indeed. (This is why we shouldn't drive a stake for a dish, or remove anyone else's ground. A stake or your body may produce a better ground than that of the house creating a potentially fatal mistake.)
In addition to the correct ground at the ground block, the dish itself needs to be grounded. The reflector of a dish collects more things in addition to the signal that you want. 1. It collects stray signals (Radio Frequency Interference). To prevent this signal potential from reaching the inner wire core (entering your system as noise and degrading your picture) the reflector needs to be grounded. By reducing the potential to zero, with a ground, these signals can be prevented from reaching that inner core as they are "drained" from your dish. And this from Dish Network training about grounding a system...This is one of the reasons to ground: " Reduces Radio Frequency Interference which can degrade the display of video signals" (from Dish Network grounding instructions)2. It collects static electricity. As the wind blows across your dish and the wires attached to it, electrons are rubbed off and collect on the dish, creating a static charge. The charge will build until it has enough potential that it will jump across an airspace to ground. (Just like when you scuff your shoes on carpet and just before you touch someone, the static spark jumps from your finger.) This charge will usually hit the LNB or follow a path to your electronic components. Static charge is one of the most common caused for LNB failure. 3. It collects voltage surges and voltage transients that result from lightning. A lightning strike need not hit your home to charge the air with quite an amount of electrical energy. The potential for damage by this high voltage electrical energy can be lessened when properly grounded. (Some of you may have been "pulsed" by lightning. You saw or heard a nearby lightning strike and your system started acting up. Your color on your TV went all wrong. Then during the week it took to get a tech out there everything had pretty much returned to normal. What happened is that the degausser on the TV did its work every time you turned on the TV, drawing the excess magnetism out of the TV and restoring the color, while the excess electrical charge on the system dissipated, returning function to your system.)
Grounding (bonding) of satellite systems includes also a connection to the O.D.U. (outdoor dish unit) as well as grounding the coaxial cable. It is not used to carry the voltage of a lightning strike to the ground, but instead it turns the dish into a lightning rod. (You would need an extremely large wire to carry the millions of volts from a lightning strike!) Despite what you might think, a lightning rod does not attract lightning but it repels it. When properly grounded the potential of the dish unit resembles the potential of the earth below it. This leaves the lightning looking elsewhere to establish its strike location. What happens is this: The wind blows across your dish nearly every moment. The wind sheds electrons onto the metal dish as is passes. The more wind you have (as in an approaching storm) the more shedding and the greater the positive charge on your dish. If your dish isn't grounded, the electron build up creates a positively charged lightning rod that attracts the lightning bolt. If, however, your dish has the proper ground wires connected, what would be an electrical build up on the dish, is instead, constantly carried to ground leaving your antenna with the exact same potential as the ground. In this way, the lightning doesn't "see" your antenna as a potential strike point because the antenna "looks" the same to the lightning as the ground itself does, and lightning likes trees and things that build up positive charges to strike.
A properly grounded system provides an alternate path to ground for electrical surges and can minimize the damage caused by line surges.
A ground loop occurs when there is more than one ground connection path between two pieces of equipment. The duplicate ground paths form the equivalent of a loop antenna which very efficiently picks up interference currents. Lead resistance transforms these currents into voltage fluctuations. As a consequence of ground loop induced voltages, the ground reference in the system is no longer a stable potential, so the signals ride on the noise. The noise becomes part of the program signal and can degrade your picture.
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You have a right to an antenna! The rule prohibits most
restrictions that: (1) unreasonably delay or prevent installation, maintenance
or use; (2) unreasonably increase the cost of installation, maintenance or use;
or (3) preclude reception of an acceptable quality signal. Over-the-Air Reception Devices Rule Send questions or comments about this web site.Copyright © 2009 WOWVision! Ministries Last modified: 01/16/10
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Why Ground?
It's the Law!
