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Skin effect is a physical phenomenon that relates to the limited penetration into a conductor of a RF signal, according to its frequency. This effect is present in coax cable, keeping the RF signal inside and any coupled outside interference on the shield’s outer surface. The effect begins to fall apart as the frequency is lowered and the penetration, which is a gradient, begins to mix the shield’s outside interference energy with the desired inside energy. A ground loop, which imparts 60 Hz onto a desired signal, is due to dissimilar ground potentials causing ac current flow between points on the coax shield and is low enough in frequency to couple energy through to the center conductor With lightning, the main frequency range is dc to about 1 MHz (-3dB). This is in the range that affects the coax transfer impedance. The thicker the shield material, the less the effect to these low frequency currents.

Corrosion Protection for Tower Structures. Most people have a tendency to use copper as for grounding because it is a good conductor, and one of the more noble metals. However, it does have a significant drawback. Since it is near the upper end of the table of noble metals, copper when put in direct contact with most common metals, which are lower in nobility, will cause accelerated corrosion of the lesser metal. The significance of being more noble means any other metal buried and connected to your copper ground system will become sacrificial. (Also see Topic: Dissimilar Metals.)

There are many different types of metals and each has desirable properties. However, when two dissimilar metals are joined to make an electrical connection there can be problems. Corrosion will begin when the connection is exposed to moisture or any other liquid acting as an electrolyte.

Any properly applied lightning protection device is only as effective as the ground system attached to it! Ground resistance (impedance) is usually measured using the 3-stake fall of potential method. Theoretically, the final measurement achieved on the completed ground system is the same resistance (impedance) to any other ground system on earth. A good ground system measurement would be between 5 and 10 Ohms. A well designed 5 Ohm ground system is usually considered optimal for a lightning ground system.

Equipment racks and cabinets can provide an unwanted path for lightning surge energy. The common practice of bringing the antenna cable into the top of the cabinet and securing (bolting) the cabinet to the floor could damage the equipment.

Fuses react very differently to transient surge current as opposed to sustained overload current conditions. Fuses and fusing concerns become complex when contained within surge suppression equipment. Utilizing current limiting fusing in any SPD can quickly become counterproductive because the device’s overall performance is hindered. These fuses greatly limit the total surge current capacity of a SPD to their own individual capacity. The causes of the hindrances are related to the various current ratings and the operational characteristics of specific types of fuses. While there are legitimate ways to compensate for this troublesome drawback, many suppressor manufacturers choose to misrepresent the facts and further complicate the issue.

Global Positioning System - GPS - has infiltrated modern life to such an extent that many people, systems and operations rely on its error-free functioning. GPS is used for navigation, synchronizing data on wireless networks and managing loads on vast power grids, making it an integral system within the transportation, telecommunication, manufacturing, electricity distribution, mining and construction industries, not to mention national defense.

The first consideration for GPS antenna placement is a clear view of the sky, preferably 360 degrees. In the usual installation, the GPS antenna is located low and close to the equipment building roof. If an outdoor cabinet, the antenna is mounted on the cabinet or very low on the adjacent monopole/tower. A direct lightning hit to the above mounted antenna is unlikely. Mounting on an equipment building roof or cabinet is the safest place since the potential rise on the outside of either of these structures would be more or less equal with the potential on the inside. The PolyPhaser protector is there to equalize the differential in potential that occurs between center conductor and shield of the coax cable on its way from the antenna to the receiver.

Before one can design a properly sized grounding system for the required fall of potential measurement, the resistivity of the soil must be known. The resistivity results will determine the conductor size, length, and number of radials required. The measurement will also determine how many rods are required, their length and their spacing on each radial.

The statement that rods should have a separation, “greater than the sum of their lengths apart,” originates from theory, and the fact almost all ground rods will saturate the soil to which they connect. A ground rod connects to localized, irregularly sized, three-dimensional electrical clumps. Depending on the soil make-up (layering, etc.), the volume of earth a ground rod can dump charge into can be generalized as the radius of a circle equal to the length of the rod at the circle’s center. This is known as the sphere of influence of the rod. The sum of the driven depths of two rods should be, theoretiin homogeneous soil, the closest that ground rods can be placed. Anything closer will cause the soil (clumps) connected in common to saturate even faster.