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Field Services: RF Measurements & Site Survey
Detailed Information

Site Audits

Comsearch personnel perform facility audits at all types of telecommunication sites. The audits are normally used to obtain parametric and component values for license applications, inventory requirements, and database creation and/or verification. The audits can also be used to determine general site conditions, such as physical conditions of towers, tower lighting operation, soundness of grounding system, intrusion alarm operation, RADHAZ signage, and emergency power system test, including Uninterruptible Power System (UPS) check out.

The audit data collection identifies:

• site coordinates,
• site ground level above mean sea level,
• tower height, antenna heights on tower,
• types and sizes of antennas,
• pointing azimuth of each antenna,
• transmission line types and lengths,
• transmitter and receiver nomenclatures,
• number of each transmitter and receiver,
• number of standby transmitters and receivers,
• tuned frequencies of all operating equipment,
• transmitter power outputs, and
• receiver input levels.

Digital photographs of all site structures, including towers, shelters, installed equipment, fenced areas, and emergency generators, are also made as part of the data collection. All of the collected data is published in a site audit report, and the data is stored in the Comsearch site and facility database.

Site Surveys for Fixed Wireless Base Stations and Customer Premise Locations

Comsearch's field technicians survey available locations to determine whether there is sufficient path clearance from potential Base Station hub sites to a customer premise. Site plots are created to designate the best location for antenna installation.

Real Estate Searches for Telecommunications Sites

Comsearch helps locate suitable properties for your telecommunications needs. Sites can be a tower, undeveloped land to build a tower or monopole, an existing rooftop of a building, or other less traditional sites. Our trained engineers will analyze your needs and find potential sites that meet the technical criteria. We take into account electromagnetic environment issues and operational requirements in the search for the best possible candidate sites.

Program Management of Telecommunications Site Development

Comsearch engineers, in concert with the full resources of our parent company, CommScope, carry out the technical management of a telecommunications site, from initial design to installation to final acceptance testing. With this service, Comsearch takes on the technical staff role for the site developer. We carry out the functions of proposal evaluator, supervisor of installation, and quality control inspector. We perform specification development as well as evaluation of test data for acceptance.

RF Radiation Hazard Measurements

With the recent adoption of specific radiation hazards standards by the FCC, it is becoming increasingly more important for owner/operators at any FCC-regulated transmit facility to ensure compliance with Maximum Permissible Exposure (MPE) limits. Comsearch follows practices and procedures specified in FCC Report & Order 96-326 to determine whether the power density levels at a given facility meet or exceed FCC-approved standards such as those presented in OET Bulletin #65 and all of its amendments, or in NCRP Report No. 86 (1986).

Comsearch offers two different testing scenarios:

• Broadband measurement instruments, and
• Combination of broadband and narrowband instruments.

The first, and more cursory, scenario utilizes broadband measurement instruments only. We use the broadband measurement instrument as a fast, reliable method of determining compliance and potential "hot spots" in and around the facility to identify general areas of susceptibility to non-compliance with MPEs. We use the broadband probe to find potential RF leakage around waveguide and cable assemblies in each of the transmitter rooms.

In the second scenario, we use a combination of both broadband and narrowband instruments. If we identify hot spots, it may be necessary to determine the exact contribution from specific transmitters. This is especially important at shared facilities where the responsibility for radiation hazard compliance is divided among several different owner/operators. For these situations, we provide an in-depth study using narrowband measurement instruments in addition to the broadband probe. Depending on the size of the facility, the number of narrowband measurement points can range from 4 or 5 to as many as 20 locations. We measure all active frequencies at the transmit facility. The narrowband measurements provide a more precise value of the power density and compliance with MPEs.

For more information, see Comsearch's Eight-step Radiation Safety Services Program.

Satellite Earth Station Measurements

Comsearch provides the following Satellite Earth Station Measurements:

• Transmit and Receive Earth Station Measurement Services
• Earth Station Blockage Surveys
• Analog to Digital Transition Measurements
• Satellite EIRP Measurements

Transmit and Receive Earth Station Measurement Services

Based upon the operational characteristics of the satellite earth station, measurements are conducted to verify or dismiss predicted sources of interference. Both the uplink and downlink spectrum can be studied and the results used to document clearance from or into other systems sharing the same frequency band.

Before going into the field, Comsearch engineers conduct an interference analysis to determine the potential impact from both existing and proposed terrestrial microwave systems. Our proprietary database is used in the analysis and contains all of the licensed, proposed, and prior coordinated microwave paths in the country. Once in the field, our engineers pinpoint the predicted interference sources including terrestrial interference, broadband noise, and harmonics and determine whether or not they actually cause interference. If they do cause interference, Comsearch proposes solutions, such as shielding, site relocation, or other interference mitigation techniques, to overcome these existing interference problems. We identify interference sources at sites before they become a problem.

Earth Station Blockage Surveys

Earth station blockage surveys are performed along identified interference paths to determine and document blockage caused by man-made or natural obstacles. This potential interference can be into the earth station downlink as is prevalent in the 4 GHz band or emanate from the earth station uplink into terrestrial microwave systems as is the case in the 6 GHz band. The results of the survey are used in the clearance and mitigation of the interference potential.

Analog-to-Digital Transition Measurements

The satellite industry is steadily making the transition from analog to digital modulation. This allows for a much-improved use of spectrum resources. However, digital signals are more susceptible to interference and earth station facilities that were previously suitable for the reception of analog signals may find the interference environment far less forgiving for digital signals. In addition to traditional terrestrial microwave interference, other sources of interference must be measured to determine whether the site is suitable for interference-free digital operation.

Learn more about Comsearch's Analog to Digital Migration Program

Satellite EIRP Measurements

Satellite signal strengths (EIRPs) often differ from the published footprints due to planned or unplanned changes in satellite position or aging equipment. Comsearch engineers perform on-site measurements of EIRP (Effective Isotropic Radiated Power) to determine satellite coverage in fringe areas of your system. We set up a portable receive earth station at a designated location. Using measured receive signal level and all known or calculated parameters, we determine the EIRP for a given area. This measurement is necessary to determine required antenna size.

Troubleshooting

Occasionally, service at an earth station or other communications facility may suddenly be compromised by an unknown source of interference. This interruption may be temporary or permanent in nature, but it can be resolved.

Comsearch combines state-of-the-art equipment with decades of experience to pinpoint the source of the interference. The source of interference can range from terrestrial interference, broadband noise, intermodulation, and harmonics to something as subtle as a lawnmower! Comsearch will recommend a solution to the problem to allow your system to operate interference free, as it was designed to perform.

Electromagnetic Interference (EMI) Testing

To determine the level of RF energy in a given area that may affect sensitive communication, network, or electronic devices, you need to conduct Electromagnetic Interference (EMI) studies for both planned and existing communications systems. Comsearch engineers provide in-depth testing services utilizing several different antennas to cover the bands of interest and monitor all RF signals to accurately assess the interference environment.

RF Sweeps for Unlicensed Systems

The use of the unlicensed microwave bands is rising at a significant pace and so also is the increased potential for interference between systems. Since these systems, by their very nature, are not licensed and centrally data based, the interference environment is unknown. Comsearch performs RF sweeps or electromagnetic scans in the unlicensed bands to characterize the interference environment and determine whether a client's plans for an unlicensed system are feasible in a given location. These measurements can be made at any and all of the three unlicensed microwave bands: 900 MHz, 2400 MHz, and 5800 MHz.

Terrestrial Microwave Interference Investigation

We use terrestrial system interference investigation to verify or dismiss predicted sources of interference that may affect your proposed terrestrial microwave path. Before going to the field, Comsearch engineers conduct interference analyses to determine the potential impact from both existing and proposed earth stations and other terrestrial microwave systems in the same band. This analysis utilizes our proprietary database containing all licensed, proposed, and prior coordinated earth stations and microwave paths in the country.

Once in the field, our engineers pinpoint the predicted interference sources including terrestrial interference, broadband noise, and harmonics and determine whether or not they actually cause interference. If the path will receive interference, Comsearch proposes solutions, such as shielding or site relocation, to overcome these problems. We will identify interference sources at a site before they become a problem.

Terrestrial Microwave Path Surveys

Pinpointing potential obstacles and determining precise coordinates, ground elevations and required centerlines of a microwave path are the foundation of a well-engineered and designed microwave path. The terrestrial point-to-point path survey is a critical part of the design process because it provides you with needed coordinates, ground elevations and required centerlines to maximize system reliability. Additionally, accurate path data guarantees regulatory compliance with the FCC and helps reduce the chance of interference into your system.

Path surveys consist of five basic steps. Comsearch observes standard principles and practices accepted throughout the communications industry in the determination of geodetic coordinates, ground elevations, and path obstructions.

Step One: Site Documentation

A microwave path surveyor performs measurements and takes photographs at the customer's site in order to obtain all necessary information for site documentation. Site documentation includes:

• Site location map showing best access route to the site
• Photographs of the site

If there is an existing tower, we take additional photographs of that tower and develop a detailed tower sketch that includes the overall tower height along with the height of all significant objects present on the tower at the time of the survey. Elevations of tower objects are obtained to within ± 5 feet.

Step Two: Site Location Verification

We verify the location of the site utilizing precision digital theodolite or electronic distance/height/angle meters. We perform the application of triangulation or resection methods from known benchmarks, spot elevations, road intersections, existing monuments, or other control points. If the area has satellite coverage, we may use global positioning system devices to locate a site or cross-reference its location.

We determine site elevation by trigonometric leveling or differential barometric altimetry referenced from known benchmarks or spot elevations. Comsearch surveyors ensure that this elevation corresponds to the elevation contours on the topographic map. We obtain accuracy to within ± 1/2 the contour interval of the topographic map.

Step Three: Identification of Critical Points Along Path

We identify critical points along the microwave path. We determine the height, width, depth, location along the path, and ground elevation at each point for all potential obstructions from one end of the path to the other. We allow for future growth of all trees located depending upon the established vegetation of the region based on a minimum of a ten-year span.

Step Four: Path Profile

We develop a path profile utilizing criteria based on the path length, geographical location, terrain characteristics, frequency band, and expected path propagation conditions. We plot each path on appropriate maps detailing all terrain elevations. We note all off-path obstacles to include potential reflective areas such as towers, open water, low flat terrain, and buildings and make clearance calculations of all potential obstructions.

We do not include factors such as rain attenuation, multi-path fading, path reliability, space diversity analysis, and other design parameters as part of the scope of work for the on-site path survey. On some occasions, survey reports may contain comments or recommendations with regard to some of these variables; however, a detailed evaluation can only be performed as a separate study upon request.

Step Five: Detailed Survey Report

Upon completion of an accurate path profile, with possible obstructions documented, we write a detailed survey report that provides suggested minimum antenna centerline height. Centerline heights are based on criteria deemed appropriate for the path in question.

The viability of the physical placement of the recommended antenna centerline will need to be verified upon review of your survey results. Required antenna sizes, space availability, structural strength, environmental impact, and zoning requirements, for example, are all critical factors that come into play when deciding the final placement of the antenna. The analysis of these parameters is outside the scope of work for the on-site survey.

Deliverables

Following the general measurement process, we prepare a report outlining our measurement procedures, calibration steps, data results, and any pertinent recommendations. We compare the calculated power density levels to the current FCC-approved standards.

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