Three pulses per event is the median. Since all towers have some inductance, leaving the tower at a point above ground will allow some of the strike current to continue on the coax line (both the center conductor and shield) toward your equipment. Do not run unprotected lines in the EMT. Delta Lightning Arrestors Lets look at a practical example of a typical cell site installation, consisting of a 150 foot [45.72 M] by 35 inch [889 mm] triangular tower and three 1-5/8 inch [41.3 mm]coaxial cables. These ports are usually the ac power connection, a telephone or control line, and an antenna transmission line. To insulate rack cabinets from a potentially conductive concrete floor some installations place cabinets on wooden platforms. The velocity factor of the coaxial cable center conductor with a fast rise time pulse can vary from 66 to 90% the speed of light. Copper strap has a large circumference and low inductance per unit length. If your tower is close to the building, the recommended grounding strap, running down the outside wall, may inductively couple some energy from the tower. Once in the ground, the inductance of a bare conductor is shunted by the earths conductivity. Polyphaser at cable entry on dual bander, Polyphaser at feedpoint on wire. For HF I've been using gas tube lightning arrestors from Alpha Delta and for VHF/UHF and up Polyphaser. The resultant molten copper is deposited into the lower mold cavity where it burns away any oxides and creates a larger fused connection. This will help minimize magnetic energy coupling into the wiring inside the building. Last Reviewed: 1/9/03, Document Number PEN1014:Where the lightning energy goes and what can happen. The lower the inductance of the system components and soil resistivity, the lower the impedance at higher frequencies, the faster the ground system could disperse electrons. Use a It may appear obvious that the use of similar materials would eliminate the galvanic problem While this is true, galvanized ground wire and ground rods are not normally recommended since the electric utility company will probably use a copper clad steel ground rod. Connect the Polyphaser body to earth ground per the Polyphaser installation instructions. Turn On Voltage of 150 Vdc. The power, telephone and coax line protectors on each of the l/Os must be mounted on the single point plate. Mixing of materials, like galvanized rods with bare copper radials, will create a battery action and the zinc of the galvanized rods will become sacrificial, dissolving into the soil. If a PolyPhaser Entrance Bulkhead with its two 6 inch [152.4 mm] copper straps were used in the previous example, the inductance path would be lowered to 2.7uH, and the voltage at the entrance bulkhead would be reduced to 5670 volts. If you find a rock layer is making the ground rod insertion difficult and you cant remove the rod to start over a few feet away, the best idea is to cut off the rod and connect it to the system. Check part details, parametric & specs updated 05 MAY 2023 and download pdf datasheet from datasheets.com, a global distributor of electronics components. Have used Polyphasers for many years at commercial sites. -bd-]. IRVINE, Calif. (PRWEB) May 06, 2021 -- PolyPhaser, an Infinite Electronics brand and an industry-leading provider of RF and data surge protection, filtering and grounding solutions, has released a new line of fiber terminal boxes, splitter distribution boxes and rack-mount panels that are ideal from communications, telecom, cable TV, surveillance and monitoring systems. Thusly you really should put your surge protectors as close to where the coax comes into your house as you can, and one antenna per protector. This rule only holds true when the soil has the same conductivity over the entire radial area. #1 Hello all, I will soon be installing a loop antenna (W6LVP) and a discone antenna (Diamond D-130N) both antennas will be connected to mi IC-R8600. surge current. Their broad customer base of Commercial, Industrial and Military users speaks for itself. AC power line protectors and control/data line protectors are connected to the single point ground to complete your defensive strategy. The more the strike energy is divided, the less there is to go to your equipment. ANY differential between any two points on the system and you get current and damage. 6 0 obj When you consider the cost of underground utilities, these and the aesthetics must be weighed. If the interconnect path is better (lower inductance and resistance) the majority of the current will bypass the house wiring. Even if abraded, it will reform and protect the metal from any further corrosion. If I had to buy new units at retail I would probably buy Polyphaser for everything. Heater vents and electrical conduits that are not grounded to the single point can become such paths. Three Techniques: Please note the below grade interconnection of the bulkhead panel with the other elements which comprise the grounding system. The magnetic fields will also be divided and could, in theory, cancel in the middle of the building. The strike energy, like water, will follow the easiest (least inductive) path to ground. One is to totally disconnect the equipment! Other house appliances may be at risk. The earth immediately surrounding the ground point will begin to take up the energy charge and dissipate the energy by propagation within its sphere of influence (see ground systems topic). All l/Os (input/output) must be protected at this single point. As the surge energy attempts to go to earth ground using the transmitter as a connecting path to the other grounds, it is likely to also use some of the internal circuitry as a current carrying conductor and cause equipment damage. The power line to the transmitter is protected and grounded at the distribution panel where the power line enters the building. Did you know that spark gap protectors with dc continuity will not work on receivers and shunt fed duplexers? If the soil at the grounding location is not very conductive, three things can be done to help the situation. Mount the PolyPhaser Surge Arrestor on the inside wall, near the MIM-LINK unit and near the floor. A buried galvanized tower section (not the J bolts) or guy anchor embedded in concrete will have some galvanic currents that could cause the depletion of the zinc coating into the concrete. PolyPhaserleads the market with its patented RF protection solutions, specifically supporting communications systems. For a better experience, please enable JavaScript in your browser before proceeding. This will be a very low current unless another path is found by these streamers. It is a common misconception to think that a lightning strike will blow up a concrete pad. The significance of being more noble means any other metal buried and connected to your copper ground system will be more anodetic and thus become sacrificial. 8 PB-M INSTALLATION SHEET . Notes:Most people have a tendency to use copper as for grounding because it is readily available, relatively economical, a good conductor, and one of the more noble metals. See QST, Aug, 2003, P 39; Optimum Radial Ground Systems. As the joint pressure is increased, the embedded particles dig into the metals and form a virgin low resistance junction void of air and its moisture. It may not display this or other websites correctly. This means establishing a single point ground system within the equipment building. Since concrete is a conductor, your equipment must not sit directly on the concrete. 90 Watt @ 30 MHz to 9 Watts @ 3 GHz. endobj I have 2 questions. We're your complete source for grounding and lightning protection components, including coaxial lightning protectors, coax shield grounding kits, copper grounding straps, grounding plates and clamps, tinned copper braid, strap-to-tower . Any signal line with a ground return through the input/output circuitry is subject to damage. Since we are dealing with a fast rise time event, the inductance of the tower and paralleled coaxial cables become the primary factor in determining the amount of instantaneous peak voltage developed between the strike point and the bottom of the tower. Similarly, ground conductors exhibit normal inductance before they go below grade. So significant, that voltages in the order of several hundred thousands volts could be present during a strike. Route all ground straps and grounding conductors so they have a gentle bending radius. If the area is not large enough, the earth connection will suffer. the product you have subscribed to. We have only seen this happen once on a mountain top in the Nevada desert. Coax protectors should be units that have dc blocking on the center pin. Install additional bare radial lines with ground rods which will effectively parallel the inductance and reduce the overall system inductance. The directly applied or induced voltages on the center conductor would roll off and arrive after the shield pulse, producing large differential voltages between shield and center conductor. Last Reviewed: 1/9/03. Any input or output (I/O) line can carry surge current that can harm equipment. The magnetic shielding is less than the basement and the inductance to ground is higher than the basement. See the PDF from PolyPhaser Testing RF Lightning Protectors without Indicators (pdf 476k) They have performed flawlessly. The single point ground plate should also be oriented with its flat side parallel to the tower for the same reason. The anode will deplete over time in the soil instead of your tower and guy anchors. If the surge energy has not been launched into the soil within the first 75 feet [22.86 meters), the inductance of the radial will prevent any further effective prorogation. After doing all this work, Mother Nature still has a way of making anything we do temporary. Trimble recommends P/N 187642 - Polyphaser DGXZ + 15NFNF-A. The ideal plan is a single point ground with no sneak paths. In my caseit's Polyphaser. Other chemicals may be present in the soil causing decreased effectiveness of the grounding materials. With a 1-1/2 inch [38.1 mm] or larger flat strap of at least 26 gauge (0.0159 inches) [0.4 mm], both surfaces will conduct the surge. Some contractors and manufacturers have now gone to the extent of tar/pitch dipping the anchors so this galvanic corrosion does not occur. This is the accelerated corrosion (loss) of the least noble metal (anode) while protecting the more noble (cathode) metal. Secondary ac power conductors are a two way street for electrons. True, the radio may still work, if it survives the house fire. The protection on each of the l/Os at the building entrance is good practice and has the advantage of keeping the strike energy toward the outside of the building and away from the transmitter. The shunt to ground inside a receiver (coil to ground for static draining) prevents the low frequency lightning energy from turning on the dc continuity protector. A strike to the power lines some distance away can conduct damaging energy to equipment. The phone connection at the street was blown apart and the lid blown 95 feet from the underground connection. The protector will shunt the majority of the strike energy to the earth ground. Ground Measurement: When the coaxial cable leaves the tower at any elevation above grade level, a voltage divider is created at the take-off point to ground. There are several ways to accomplish this. Every conductor has measurable inductance. stream This is fine, but what if your ground has deteriorated over time or was never very good because of yard size? The protectors must be grounded to each other as well as to the tower ground. [Notice:for RF purposes the ground rods are not necessary. If the outside (tower/perimeter) ground has a low impedance at lightning frequencies, most of the strike energy will be dispersed into the ground and little energy will enter the shack. Depending on ground conductivity, harmonic and other currents, there could be current flow causing a spark when connected. Such currents following a round-member conductor will not make extensive use of its large cross sectional area. Throwing the coax out the window is not a solution, especially if the coax has already entered the house from the antenna or the antenna is roof mounted without a ground path. The phone box on the house side was blown off the house (we have underground utilities.) I once blew the traps in my Mosley TA-53 but never had any problem with the Polyphaser gear. (73, KF4MT) Last Reviewed: 1/9/03. Also fundamental to a good protection scheme is the creation of asingle point groundwithin the ham shack. Be careful when connecting a ground system to your electrical utility ground rod.