Transmission Line Sweeps

At least one ANRITSU-certified technician will use the proper sweeptester to perform your sweeps per the manufacturer’s instructions and per industry standard operating procedures. ComSite Construction test technicians are thoroughly trained in testing methods and tower safety. We use the top test equipment for this kind of testing: Anritsu. All of our Anritsu Site Master TDR units, test cables, and OSL (open, short, load calibration kits) are calibrated once yearly at the factory with calibration certificates accompanying the sweep report.

Underperforming antennas and cables cause signal loss, reduce transmission efficiency, and increase power consumption. By conducting the recommended line sweep tests on antennas or cables per the relevant standards and practices, we can identify where problems exist and make recommendations that will protect you against these losses.

ANRITSU_SITEMASTER_S820DLine sweep tests of antennas and cables fall into two general categories of testing:

  1. Resonant frequency testing.
  2. Standing Wave Ratio (SWR) testing.

But what do these tests actually mean?

Resonant frequency of cables. All low-loss cables are prone to resonating, and the resonance is a function of their length. The cables vibrate in response to energy applied to them (think of what happens when someone plucks a string on a stringed musical instrument, such as guitar). What you get is a voltage oscillation that rides on top of the intended waveform. Any antenna system is designed to accommodate particular resonant frequencies, so when the resonance of a cable is out of spec the system under performs. The resonant frequency can change for a variety of reasons.

Resonant frequency of antennas. The resonant frequency of an antenna is the center of its bandwith. Thus, if the resonant frequency of the antenna is out of spec you don’t have the bandwidth the designer intended. Changes to the physical properties of the antenna can shift this frequency.

SWR of cables. By comparing the measured standing wave ratio of a cable to its specified SWR, we can determine if a cable needs to be replaced. Actual SWR can deviate from the design SWR for a variety of reasons, including:

  • Mechanical damage during installation. Mistakes include walking on the cable, exceeding its bend radius, using too much pull tension, and pulling around sharp edges or corners.
  • Mechanical damage after installation. Assuming the cable is properly installed and protected from mechanical damage, this is fairly rare. The most common cause is damage from instrusive insects or rodents.
  • Transient damage. A direct lightning strike, though unlikely, can fry these cables. But a lightning strike some distance away can result in damage from high voltage transients. Though transient protection tends to eliminate this as a cause, exceptions do occur. The high energy can perforate the insulation jacket of the cable, leading to cable failure.
  • Age. Yes, it does take its toll.

SWR of antennas. In a perfect world, you’d have a perfect match between all elements of an antenna system and thus have an antenna SWR of 1:1. Power engineers also talk about a power factor of “unity” (100%) which is also a perfect match, but in the real world they are thrilled to get 95% (typically by adding capacitors to offset inductive loads) and often settle for much less.

Testing the SWR of your antenna allows us to “take the temperature” of your overall system performance. If the SWR is too low, we can recommend further testing to identify what’s going on. In many cases, our experienced technicians can make immediate recommendations for factors to correct.

We can save you money, by putting your antenna inspections, line inspections, and tower inspections on the same program. We offer specialized services that allow you to know the condition of your antenna system:

  • Inspections. Our standard inspections for maintenance include: a site visit with climb, visual inspection including foundations, hardware check, inventory, and color photo-documentation reports.
  • Sweeps and Line Testing. Our personnel are trained in TDR and FDR transmission line and antenna testing with a variety of sweep testing devices. Documentation is provided in chart or report form for reference and analysis. All testing is done with either an Anritsu Sitemaster (TM) or equivalent machine by a factory trained specialist. Custom sweep testing and documentation is also available.
  • Reports. Our extensive customizable reports are accurate and easy to read. Inspection reports, engineering reports, structural analysis reports, and installation detail documentation are just a few of the professional reports that we provide. These professional reports provided are bound, extensive, and easy to read. All antenna tower site reports and foundations analysis reports have detailed color photos.

xtower-installation.jpg.pagespeed.ic.fqjWCP359yWhy not have the experts fix what’s wrong? We offer several maintenance and repair services, to keep your antenna systems and their structures running reliably:

  • Analysis and repair.
  • Foundation inspection and analysis.
  • Installation.
  • Plumbing and tensioning of guyed towers.
  • Structural analysis.
  • Structural upgrades.
  • System decommissioning.
  • Tower and foundation maintenance.
  • Tower removal, where needed.
  • Troubleshooting.

For more information or to schedule your line / antenna sweep, feel free to contact us or call 888-684-6248. We look forward to working with you.