Chapter 4: Evaluation & Testing

2. The Grid Testing Methodology

The core acceptance test mechanism is grid testing: dividing each floor into a defined number of roughly equal areas and measuring signal at a representative point in each one — turning "is this floor covered?" into a specific, repeatable, countable procedure rather than a subjective walk-through.

The 20-Area Grid

• Each floor of the building is divided into 20 approximately equal test areas.
• One test point is measured per area, typically at or near the center of that area.
• For larger floors — commonly those at or above roughly 32,000 square feet — some jurisdictions instead divide the floor into a grid of approximately 40 ft. by 40 ft. cells, a related but distinct sizing approach from the 20-area method.

Critical Areas Are Tested Separately

Critical areas — fire command center, exit stairways, elevator lobbies and cabs, fire pump rooms, standpipe/sprinkler valve rooms (Chapter 1, Section 4) — are not counted toward the 20-area grid total. They are tested individually, as their own dedicated test points, precisely because their stricter 99% coverage requirement can't be adequately represented by a handful of grid squares sized for general floor area.

3. Pass/Fail Tolerance & the Statistical Retest

Grid testing doesn't require a perfect 20-for-20 result to pass — but exactly how much failure tolerance is allowed depends squarely on which code edition governs the project, extending the same theme from Chapter 1's NFPA 1221/1225 discussion into the testing phase.

The 40-Area Statistical Retest

If the initial 20-area grid exceeds its allowed failure count, the floor is not automatically failed outright — it can instead be re-divided into 40 approximately equal test areas for a more statistically representative retest. This finer-grained retest allows a somewhat higher absolute number of failed points to still pass, since 40 smaller areas naturally produce more individual data points than 20 larger ones. If the system still fails at the 40-area level, the system itself must be altered — additional antennas, adjusted gain, or other design changes — to meet the coverage requirement, rather than being retested indefinitely at the same configuration.

4. Coverage Thresholds, DAQ, and Alternative Metrics

At each grid point (and each critical area test point), two things get measured together: raw signal strength and voice intelligibility. Chapter 1 introduced both concepts during planning; this is where they get measured for real.

Alternative Predictive Metrics

Some testing methodologies also reference bit error rate (BER) and signal-to-interference-plus-noise ratio (SINR) as alternative, more technical predictors of usable coverage — for example, a BER at or below roughly 2.5% combined with a SINR of 18 dB or better can indicate acceptable coverage even in an area that doesn't independently clear the -95 dBm threshold. These metrics are generally used as supplementary technical analysis rather than as a replacement for the primary dBm/DAQ pass criteria — always confirm with the AHJ which specific metrics they accept as the basis for pass/fail determination.

5. VSWR & Cable/Antenna Analyzer Verification

Grid testing verifies coverage as experienced by a radio in the building. A separate set of measurements verifies the health of the physical RF chain itself — the cabling, connectors, and antennas installed in Chapter 3 — using a handheld Cable & Antenna Analyzer (equipment from manufacturers such as Anritsu and Viavi is commonly used in this role).

VSWR — Voltage Standing Wave Ratio

VSWR measures how well-matched an antenna and its feedline are to the RF equipment driving them. A perfect match reflects a theoretical VSWR of 1.0:1 — no power reflected back toward the source. Any mismatch (a damaged connector, a kinked cable, a poor antenna match) reflects some power back, which both wastes transmit power and can stress amplifier components.

A VSWR reading of 1.5:1 or better is the widely used professional target. A high VSWR reading during acceptance testing is a strong indicator of a physical installation defect — most often a damaged or improperly terminated connector, water intrusion in a connection, or physical cable damage — that should be traced and corrected rather than accepted as-is.

Uplink/Downlink Frequency Verification

The same class of analyzer is also used to confirm the BDA is actually operating on the correct, agency-licensed frequencies in both directions, and to re-confirm the isolation value between donor and server antennas (Chapter 3, Section 4) as a final field check — not just relying on the value measured during commissioning, but re-verifying it as part of the formal acceptance record.

6. Documentation, AHJ Sign-Off & Ongoing Recertification

A successful acceptance test is not the final step — it has to be properly documented and formally accepted before the project's ultimate goal, the Certificate of Occupancy, can be issued (Chapter 1, Section 3).

The Acceptance Test Report Package

• Test methodology used (grid spacing, equipment, code edition applied)
• Test point locations, marked on floor plans
• Signal strength and DAQ measurements at every point, both uplink and downlink
• Pass/fail summary by floor and by critical area
• VSWR and isolation measurements
• Installed equipment list and technician certification documentation (Chapter 3, Section 2)
• A signed Certificate of Commissioning, typically completed by the approved installing contractor and countersigned by the building owner's representative

Closing the Loop: Annual Recertification

Passing the initial acceptance test and receiving the Certificate of Occupancy is not the end of the system's compliance obligation. ERCES installations require ongoing periodic recertification — commonly annual — where the grid testing, VSWR, and supervision checks covered in this chapter are repeated to confirm the system still performs as it did at initial acceptance. Equipment ages, batteries degrade, buildings get renovated in ways that change RF propagation, and donor signal conditions outside the building can shift over time. Recertification exists to catch that drift before it becomes an undetected coverage gap.

This closes the full lifecycle covered across this training series: a Planning phase that determines whether ERCES is required and which standard governs it, a Design phase that engineers a system to meet that standard, an Implementation & Commissioning phase that builds and correctly configures that design, and an Evaluation & Testing phase that verifies, documents, and — on an ongoing basis — reconfirms that the finished system actually protects the people who depend on it.

Final Assessment — Chapter 4: Evaluation & Testing

Answer all 10 questions. A score of 80% or higher (8 of 10) is required to pass and receive your certificate.