Calibrating Equipment

Anyone involved in the mayhem of keeping a wireless communications network functional and profitable knows the devil can be in the details. Although it may seem unlikely, a pro-active plan for test and measurement (T&M) equipment calibration may be just the defense you need to win the detail battle. Here's the strategy.

KNOW WHY TO CALIBRATE You know you ought to have a plan to calibrate your T&M equipment, and yet, it is one of those chores that consistently gets bumped in preference to putting out hotter fires. What you may not know is that out-of-calibration equipment could be silently fueling those flames.

Consider the technician who drives three hours to reach a cell site and spends the rest of the day (plus some overtime) taking measurements and making adjustments. If the T&M equipment he is using is calibrated accurately, he's probably prevented a few fires and put out many others. If, however, the equipment he is using to tune the cell site has drifted out of calibration, the problems will flare. Furthermore, if the equipment has been out of calibration for some time, it may be the source of degraded service quality and lost revenue.

In a perfect world, a cell technician is responsible for no more than 12 sites and follows a rotating 3-month preventative maintenance schedule. However, the geographic realities of site maintenance and the additional demands on the technician's time, such as bringing new sites on-line and responding to trouble calls, may result in one cell-site tuning visit every six months. Because site visits are sparse and usually require taking the site out of service, accurate readings and adjustments at each visit are critical.

Just how consequential are a few watts or hertz? Very. If, for example, a technician tunes an analog site with a radius, or footprint, of 100 miles to transmit at 80W (instead of 100W) due to faulty T&M equipment test results, revenues from that site will decrease significantly because the service footprint will shrink. Meanwhile, the competitor in the adjacent cell may capture your connections -- and revenue -- because your signal is too weak to get the subscriber to your next cell. Irritated customers will complain of dropped calls, calls not connecting, and noisy or weak connections.

On the other hand, if the site is tuned an errant 20W higher than called for by regulation, bleed-over into another carrier's footprint could yield time-consuming, finger-pointing disputes and costly FCC sanctions. Regaining lost ground carries a high price. You can double, maybe triple your labor budget to cover retracing trips to each of the inaccurately tuned sites. Then, you can factor in lost revenue for reduced network capacity, as well as contracts canceled by unsatisfied customers while the network is being retuned.

ACCEPT DRIFT & DEAL WITH IT Because ideal conditions exist only in laboratories, T&M equipment manufacturers develop instruments to endure anticipated stresses while functioning accurately within defined parameters over time. Factors including environmental conditions and minor inaccuracies in the equipment manufacturer's own calibration equipment are compensated for so that product performance will be within specifications. As equipment ages, however, it often will drift out of calibration, yielding unreliable test results.

For example, if test equipment accuracy is normally within 1dB of actual, the reading falls into the acceptable range of measurement. Any actions taken by the technician based on these results would promote efficient site operation. If the equipment has not been calibrated according to the manufacturer's schedule and has drifted, it could yield an "acceptable" measurement that is actually outside the acceptable range. Actions taken based on such readings will lead to situations similar to those described previously.

CONSIDER ALL ANGLES A comprehensive calibration plan encompasses both a policy and a defined procedure. As a component of a responsive operations-management plan, equipment calibration will support your company's commitment to providing subscribers with top-quality, reliable service while helping to ensure the most effective use of equipment maintenance dollars.

There is no magic recipe for developing a calibration service plan; however, there are guidelines that can lead you safely through the process. As you develop your plan, take into account the following factors:

* Know when to calibrate.

This is the easiest step in your strategy; follow the test equipment manufacturer's recommended schedule. In product research and development, T&M equipment manufacturers develop theoretical calibration intervals based on the specifications provided by the component suppliers. The manufacturers refine these intervals based on actual drift measurements taken on equipment over time.

A word of caution: If you encounter test equipment that "requires no calibration" or is touted as "self-calibrating," proceed with care. Manufacturers can incorporate circuitry in testing equipment that automatically initiates calibration routines at equipment start-up. However, these routines are based on internal reference points that, by the laws of nature, will incur drift over time and ultimately yield inaccurate calibration. External calibration by a standard traceable to a universally accepted and proven measure, such as the frequency of an atomic clock, is necessary to ensure that the effect of nature's constant thrust toward entropy does not jeopardize your testing integrity.

* Decide whom to trust to calibrate your calibration equipment.

Deciding whom to trust with the responsibility of calibrating your T&M equipment is perhaps the most difficult aspect of developing your strategy. Three choices are available, and each offers benefits and drawbacks that must be weighed against your individual considerations.

1. OEM -- No one knows the equipment better than its manufacturer. An OEM will have the proper equipment and established procedures to calibrate your instrument correctly. For added time and cost savings, the OEM can perform equipment repairs and usually will incorporate any product updates at no charge while the equipment is in the shop. Look for manufacturers that operate separate production and repair departments; a standalone repair department generally will turn equipment around more quickly.

2. Third-party calibration vendor -- If you use T&M equipment from various manufacturers, a third-party provider will enable you to consolidate all calibration at one location. Look for a provider that is certified by the OEM, and determine whether the provider offers the expertise and facilities to perform repairs at the same location. Third-party providers often offer pick-up and delivery services. Avoid third-party providers that simply serve as "middlemen" by picking up your equipment and then subcontracting the calibration to another vendor or the OEM. This "service" can lengthen the time you will be without your test equipment and inflate the cost.

3. In-house -- Many T&M equipment manufacturers will provide customers with calibration procedures, allowing users to service equipment at their own facilities. Although this option offers you the highest level of control, you must absorb the costs of setting up an internal calibration operation and ensure that calibration tasks do not detract from the core competencies and responsibilities of staff.

If the choice is not immediately clear, look deeper. Both OEMs and third-party providers may offer value-added options including loaner equipment, expedite options, reminder notices and packaged service plans. Each service addresses needs that may make one option stand out as the best choice. Before sending your equipment out for service, weigh the vendor's depth of knowledge on your specific instrument against convenience and cost. A third party may be the most economical choice for calibrating instruments that function on mature principles such as oscilloscopes and decibel meters. However, for high-end, application-specific instruments, the OEM usually delivers the best value.

* Follow through on your plan. Undoubtedly the wireless industry will continue to be called upon to deliver more services by a demanding marketplace, and system integrity will remain paramount to revenue growth. As an increasing number of subscribers move toward application-driven, data-intensive wireless phone use, transmission equipment accuracy must keep pace. Regular T&M instrument calibration is an important consideration in meeting these future needs. Only providers with efficient operations, including technicians armed with the proper test equipment in optimum working order, will have a chance of winning the battle.