Prime contractors to cellular network operators (turf vendors) and their sub-contractors have a lot to do when building new cell sites or modifying existing towers. When new RF cables and antennas are installed, they need to be “swept,” a process that uses electronic test equipment to check for faults that will affect the RF radio signal. Sweeping the cables and antennas and preparing the line sweep reports can be a particularly “interesting” part of the job.
Towers have at least six, and perhaps 30 or more cables and antennas. Each one of these cables and antennas typically needs to be checked for RF faults, separately and in various combinations, by using a cable and antenna analyzer such as an Anritsu Site Master™. The method for doing this is normally specified by a method of procedure (MOP). This MOP often requires six or seven different sweeps per cable, which means 36 to more than 180 line sweep measurements per tower. If the cables and antennas must be swept for passive intermodulation (PIM), more than 320 measurements may be generated for each tower.
Which trace types are required?
Trace types for each cable and antenna mounted during construction commonly include:
- Antenna return loss
- Cable return loss
- Cable insertion loss
- Cable distance-to-fault with a calibrated 50 Ohm load on the far end
- Cable distance-to-fault with a calibrated “short” on the far end
- Antenna and cable system return loss
- Antenna and cable system distance-to-fault
For PIM measurements, these additional trace types may also be required for each antenna/cable combination mounted during construction:
- Antenna PIM level
- Cable PIM level
- Cable distance-to-PIM
- Antenna and cable system distance-to-PIM
What is involved in processing these traces?
Processing these traces and preparing the required report can often take longer than the cable and antenna sweep itself. This is partially due to the naming requirements typically included in the MOP. Since most line sweeping gear cannot generate the lengthy names required, the files need to be touched twice; once when saved on the instrument, and once before being turned in. Report requirements include:
- Trace file names must meet often complex network operator standards.
- Trace titles and subtitles (visible when viewing the trace) also need modification.
- Four markers, in some trace types, need to be checked and, if necessary, set to specific frequencies.
- Two more markers, in some trace types, need to be set to the highest values in a specific range of frequencies.
- The limit line needs to be set at the right value, if it is not already there.
- Some trace types then need to be judged for passing, or not passing, the MOP criteria.
What this means is that a tower with 36 lines might be swept in three hours, but processing the resulting 180 (approximately) traces could take up to five hours. If after processing, any of the traces are found to fail, technicians will need to re-visit the site to fix the issues and take new sweeps, which is additional time and expense.
Manually generating this report takes time and is an error-prone process, particularly when the technicians are in a rush to get the towers up. Reviewing the reports also takes time. Re-testing due to errors detected late in the process takes even more time. In the ultimate irony, typical turned-in reports have errors on approximately 5% of the traces, leading to still more confusion, record-keeping errors, and rework. There is a better way to generate a sweep report.
Automated line sweep reporting system
There is a semi-custom web-based tool from Anritsu, called Sweep Master Pro™, that does much of this work automatically. It can reduce hours of report preparation to just minutes, and potentially reduce a 5% error rate to zero.
This Web app requires field technicians to save their traces with an easily defined naming format. This short name, or field name, includes just enough information that the Web app can identify the trace and know which tower, sector, cable and test type it represents.
Once identified, technicians place the sweeps, or measurement result files, into a common directory and log into the Web app, Sweep Master Pro. The Web app organizes geographic and site information, project contact information, trace uploads, trace viewing and trace judgments. It also has methods to extract data for use in other reporting systems.
Traces that conform to the simple field naming convention (an eight character alpha-numeric code) can be uploaded all at once with the “Bulk Trace Upload” capability. This utility takes two or three minutes to upload 200 traces. In that time, it renames the file name, trace title and trace subtitle to network operator standards, sets all markers and limit lines to the right place for the type of measurement, and does a pass/fail judgment on the traces, using standards defined by the network operator for this job.
If there are a few traces that do not conform to the simple field naming convention, they can be uploaded with the “Multi-File Upload” capability. This allows technicians to identify traces to the system individually.
Once uploaded, technicians can view the results and know immediately if the traces meet network operator standards or not. If the technicians have uploaded traces using an air card at the job site, they now have the information necessary to re-sweep, or even repair, a cable before they leave the job site, greatly speeding up any needed rework.
Traces can only be uploaded once in any project. This trace identification capability prevents accidental or deliberate uploads of duplicate traces and ensures the integrity of the trace data.
Once uploaded, the construction manager or RF engineer can be notified automatically. Reviewing traces is much quicker when the Sweep Master Pro Web app has already completed a pass/fail analysis on the traces and set them to red or green depending on the results.
After review, engineering staff can accept or reject the site traces, and leave notes or comments. Everyone involved is automatically notified when this occurs.
Finally, when the site is accepted, Sweep Master Pro allows quick generation of PDF or ZIP files to serve as a long term record.
Does it work in the real world?
A prime contractor in Utah was able to use Sweep Master Pro to reduce a 5% error rate to 0%. In the process, they reduced their cable and antenna line sweep and reporting time by 66%. They reduced costs by 33%. The cost savings was very helpful when they bid on their next job.
In addition they reduced unneeded truck rolls, received results faster, and gained overall better visibility of the project progress, which greatly benefited the project manager.
Finally, the low error rate impressed the network operator and strongly contributed to retaining their preferred vendor status.
Anritsu Sweep Master Pro is a Web application that can dramatically reduce line sweep reporting errors and reporting time. It provides a win for sub-contractors by speeding up reporting, minimizing rework and reducing cost. It provides a win for prime contractors, or turf vendors, by providing accurate data faster, helping to keep projects on schedule, and lowering their costs. It provides an advantage for wireless network operators because it delivers error-free data, helps keep projects on schedule, and helps keep costs under control. Anritsu Sweep Master Pro™ is a win, win, win solution.
Learn more here.