How to Select Lightning Dissipation Systems for Towers and Antennas Hear No RF Evil - See No RF Evil

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How to Select Lightning Dissipation Systems for Towers and Antennas Posted: 25 Jul 2012 09:17 AM PDT LBA Static Dissipation Systems are designed to prevent lightning strikes to your tower and antennas.  These systems have been around for many years in a number of forms, with a proven track record. Keeping in mind that there are no guarantees with any lightning protection system, there are some guidelines to be considered when selecting the appropriate system for maximum protection of your structures. These systems have a bit of an identity crisis, having been called static dissipators, static dissipation arrays, streamer-delaying air terminals, lightning dissipaters, static charge dissipation arrays, spot dissipaters, linear array dissipaters, streamer emission delay terminals, and more! All these names refer to devices using point discharge phenomena to retard and reduce the potential of lightning strokes to their protected devices. Towers and antennas are prime lightning targets! Choosing the appropriate dissipater for a specific application requires a number of performance issues be considered such as: radius of dissipater electrode cross section, construction material of the dissipater, number and density of electrodes and the configuration of the dissipater on the structure it is designed to protect. Different forms of devices are used to protect tower or mast tops, and the attached items like antennas, meteorological instruments, lighting devices, sailboat rigging, and a host of other things. The radius of the dissipater electrode cross-section   is important. The laws of physics indicate that a sphere one centimeter in radius has a maximum charge breakdown of about 30,000 volts, depending on air pressure, temperature and humidity. At this point discharge into the atmosphere occurs. As the radius is reduced the amount of charge potential also reduces preventing the buildup of ground charge, thus preventing a strike. Sailboat mast and light protected by a dissipater air terminal The number and density of dissipater electrodes or ionization brushes also plays a vital part in choosing the dissipater array. Dissipater needs are determined by the structure to be protected and rate the dissipation should occur to prevent a strike. The density is important as they must not be too close to one another causing inter-point interference. LBA dissipaters have been optimized for these characteristics. Conductivity and durability are vital qualities in the materials used in static dissipation arrays. Obviously the system must have a long life and give good service. Ionization brushes are typically made of stainless steel. A good conductor must provide maximum discharge of current during operation. A properly constructed dissipater, such as those from LBA, is constructed to absorb a lighting strike, in the rare case that occurs. The best dissipaters conform to UL and NFPA codes for air terminals. Often, UL-listed dissipater air terminals replace conventional "lightning rods" in code-compliant building and structure protection systems. LBA dissipater air terminals are UL-listed and are used in this manner. The natural dissipater points inherent in all objects are a place to start in configuring dissipation on a structure. The natural dissipation points typically occur at the top and corners of the structure or antenna.  Enhancing these natural points on the structure is the most effective way to support the charge dissipation function.  As a practical matter, the array configuration should be tailored to the structure and not the other way around. Tower sideflash dissipater assembly There has been controversy about whether or not static dissipater systems work. The discussion ranges from yes they definitely do to no they definitely do not work. There are no guarantees of perfect performance. Often, poor performance has been tied back to improper design and application. Where there is consensus it is on the fact that static dissipation does no harm, but there is a wide body of empirical evidence that well designed systems provide cost effective protection of structures from the damage caused by lightning strikes. In the final analysis, the buyer's objective is finding a cost effective technology to reduce the threat of lightning strikes to his critical infrastructure. In choosing the appropriate system, the buyer should assess the availability of technical assistance for the technology selected, the installation cost, the quality and ease of installation and the manufacturer's service after installation. Here is how a GPS community base station used static dissapaters available from LBA for lightning protection, as described by Utah County, Utah staff: Utah County Communications uses antenna dissipation systems "A concern in the installation of the system was the antenna’s vulnerability to lightning strikes since the area in which the Security Center is located boasts one of the highest lightning strike counts in the valley. The grounding and lightning arrestor system in place on the telecommunications tower provides a high degree of protection. However, in addition to this system, we decided to install a static dissipator system and an antenna cable surge suppressor". LBA can assist you in protecting against lightning We offer a range of qualified and code-compliant static dissipation systems at http://www.lbagroup.com/international/tower-lightning-protection.php#tower. Our applications are backed up by a professional engineering staff.

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fieldSENSE ProHD® RF Personal Monitors Verified By ACRBR Hear No RF Evil - See No RF Evil

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fieldSENSE ProHD® RF Personal Monitors Verified By ACRBR Posted: 17 Jul 2012 08:49 AM PDT The ProHD® fieldSENSE personal RF monitor was recently put through rigorous validation testing. This work was carried out by the noted Australian Centre for Bioeffects Research (ACRBR) at Swinburne University of Technology in Hawthorn, Melbourne, Australia. ACRBR independently tested the fieldSENSE monitor operation for continuous wave (CW) exposure and also for signals representative of real signals found at typical mobile base station transmitter sites. Two sample fieldSENSE monitors (one occupational, one public) were provided by EMSS for calibration. The fieldSENSE monitors are stand-alone, battery powered, handheld devices designed for use by technical personnel working in the vicinity of mobile base station antennas. They give the user an indication of the radiofrequency (RF) electric (E) field exposure level relative to either the occupational or public reference levels prescribed by exposure limits in a nominated standard. The sample units provided for this calibration were designed to indicate relative exposure to the 1998 EMF exposure guidelines issued by the International Commission for Non-Ionising Radiation Protection (ICNIRP). fieldSENSE Monitor Under Test This calibration set out to assess whether the sample fieldSENSE devices that were provided perform within the manufacturer's uncertainty specifications, with due regard to the uncertainty of the ACRBR calibration procedure. The manufacturer EMSS has calculated the uncertainty in the E-field response of the fieldSENSE devices to be +3.3 / -3.6 dB over the full frequency range of operation. The fieldSENSE monitors were calibrated for all seven LED response levels at 900 MHz and 1800 MHz (CW), and for the highest three of the seven LED response levels for GSM and DMA modulated signals.  The tests were conducted by Dr. Vitas Anderson and Ray McKenzie. The tests found that performance of the ProHD® fieldSENSE RF monitors was well within the manufacturer specification for all tested modalities. For CW exposures at 900 and 1800 MHz, and in the configuration tested, the average error across all LED levels in E-field response of the sample occupational and public fieldSENSE monitors ranged from – 1.29 dB to +2.09 dB. This is well within the factory expanded uncertainty specifications of +3.3 / -3.6 dB. Compared to CW exposures, the fieldSENSE monitors responded differently to the digital modulated signals of GSM and WCDMA mobile network signals by up to 0.85 dB. However, these differences still place the fieldSENSE monitors well within the factory expanded uncertainty specifications of +3.3 / -3.6 dB. Download the full testing report here. More about the fieldSENSE ProHD® monitor and your purchase connection is at http://www.lbagroup.com/technology/fieldsense-personal-rf-monitor.php.

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Do Personal RF Monitors Need Recertification? Hear No RF Evil - See No RF Evil

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Do Personal RF Monitors Need Recertification? Posted: 16 Jul 2012 01:33 PM PDT The use of RF personal monitors is becoming widespread among wireless tower climbers and technicians. This is a relatively new development of the last two years or so. Prior to that, only a few monitors were in use. These were typically models developed for use by engineers, with a host of features not needed for routine climber protection. Consequently, they were expensive and not frequently used. As safety managers have begun to require all personnel working on wireless facilities to have personal monitors among their personal protective equipment, a new generation of cost effective equipment has emerged. Typical of these monitors is the now discontinued SafeOne®, and the currently popular fieldSENSE ProHD™. Thousands of these monitors have been put into use. Many safety managers are concerned about testing and validation of critical safety equipment, including personal RF monitors. That raises the questions "When do monitors need recertificaton?" and "Who can perform recertifications?" When do monitors need recertificaton? Most manufacturers recommend a functional calibration or recertification every two years from the date of the calibration certificate include in the original purchase. LBA agrees with this advice, but cautions that an annual check may be desirable for instruments frequently used outdoors and in a construction or climbing environment. In any event, a function test by the user is advised prior to each day's work. There is no practical way to validate RF performance in the field. However, if the function test is abnormal, or the RF monitor alarms are inconsistent with those of nearby units worn by coworkers, then the unit should be submitted for recertification. Who can perform recertifications? The services of a specially equipped laboratory are required to verify that operation of a personal RF monitor is within the manufacturer's specifications. Because the occupational MPE's monitored represent high levels of RF power, this circumstance must be duplicated in the lab. Each recertification requires a high power amplifier, specially calibrated antenna, a monitor positioning device, and a shielded enclosure – an unusual and pricey set of equipment. Lab personnel must also be familiar with personal RF monitors and have access to manufacturer's data. LBA maintains a lab facility suitable to test SafeOne® and fieldSENSE ProHD™. Calibrations are supervised by iNARTE-certified EMC engineers. LBA believes its facility to be the only one specifically dedicated to these monitors. Other labs having suitable equipment, but not regularly testing these monitors, may be expected to charge several times LBA's rates for one-off setups. What is included in an LBA recertification? Each submitted monitor is given a physical exam for general condition. If in physically good shape, the batteries are replaced and the monitor is cycled through its functions, and their performance validated. Successfully passing this performance check, the RF monitor is positioned in a test fixture in the RF test chamber. Calibrated RF fields are applied to the monitor at four different orientations, and conformance to the manufacturer's requirements for that condition is verified. On successful completion of the recertification sequence, a date sticker is applied, a pass-fail record of tests is completed, and the monitor and documentation are returned to the submitter ready to be placed back in service. If the monitor fails to pass at any point, or if problems are found that would suggest end-of-life, the submitter is notified with options. As a practical matter, repairs may be expected to be a significant part of the cost of a new monitor, and are not recommended. Usually, the best action is to authorize shipment of a new replacement monitor. Because of the safety hazard presented, known defective monitors should never be returned to service, and should be destroyed to avoid inadvertent use. What does recertification cost? LBA charges $155.00 per monitor, which includes return surface shipping in the US. Turnaround time at LBA is normally five business days. For assistance on personal monitor calibration, or to purchase new monitors, contact Betty Perez at bperez@lbagroup.com or 252-757-0279.

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Popular LBA RF Safety Awareness Course Updated Hear No RF Evil - See No RF Evil

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Popular LBA RF Safety Awareness Course Updated Posted: 12 Jul 2012 10:28 AM PDT AM Detuning Systems require RF awarness In response to customer requests, the LBA RF Safety Awareness course for wireless workers has been updated to include a new section on AM detuning hazards. The new edition also includes revisions to other sections. Byron Johnson, course administrator said "We encourage feedback from our users, and strive to make our RF safety courses totally relevant to the evolving certification needs of the wireless infrastructure industry." Earlier, a Spanish language edition of the RF Awareness course was release to ensure that primarily Spanish speaking workers in the US and abroad were properly trained. Since its inception, a management feature has also been added to facilitate safety managers' recordkeeping and tracking of personnel certifications. AM detuning has become a safety concern as the number of detuned towers has increased in the wireless ecosystem. Detuning is performed when a wireless tower is located near an AM broadcast tower. It consists of rigging the tower with a cage of wires and a tuning box to neutralize the impact of the tower on the AM station. Significant energy can be coupled from the AM station, making the detuning cage wires "hot" with RF. Rarely sufficient to cause direct injury, the AM RF can cause shock and burn startle responses and precipitate secondary injuries. The course now prepares workers to recognize and manage these exposures. Learn more about the RF Awareness courses here. You can sign up directly 'On Line' from the webpage. The course is only $129, or $110 for groups of five or more. The course may be taken at the trainee's convenience, and a certificate is available for download after successful completion. Byron reminds the hundreds of past certified persons that refresher training is recommended annually. A special "reup" credit is available for those re-certifying. For assistance, contact Byron at byron.johnson@lbagroup.com or call him at 252-757-0279.

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