Acceptance Test Dispute Over Scanner Measurements
During acceptance testing of a 20-story mixed-use building, the contractor presents results from a handheld scanner connected to a rubber duck antenna. The report claims 96% general-area coverage and 99.5% critical-area coverage, with signal levels above -95 dBm. The AHJ rejects the test because DAQ was not measured and the scanner is not a calibrated public-safety receiver. The building has a 700 MHz P25 system, a BDA with 12-hour battery, and several tenant spaces that were locked during the original test. The contractor used a 50 ft grid, did not test uplink, and did not enter locked tenant spaces. The report also omits the battery load test and donor-site noise check. The contractor argues that the scanner's RSSI is conservative and that retesting will delay occupancy. The fire marshal requires a valid acceptance test before issuing the certificate of occupancy.
1. Assess the validity of the contractor's test report for code acceptance.
Read the worked answer
The report is not valid acceptance evidence. A scanner's RSSI can indicate signal presence but does not measure DAQ, which is the intelligibility metric the code requires. A rubber-duck antenna and scanner are not a calibrated public-safety receiver, and the test did not verify inbound portable-to-donor performance. A 50 ft grid may miss small dead spots, and locked tenant spaces leave untested areas. The report omits the battery load test and donor-site noise check. The contractor's argument that RSSI is conservative is not sufficient; the AHJ needs DAQ 3.0 and both directions. The correct response is to reject the report and require a retest with calibrated equipment and access to all spaces. The scanner data can be used as a screening tool, not as the basis for occupancy.
2. Design a proper acceptance test plan for this building.
Read the worked answer
Use a calibrated public-safety portable or test receiver on the actual system channels. Measure DAQ 3.0 by listening in both directions: outbound from the donor site to the building, and inbound from a portable inside the building to the donor. Record signal level at each grid point. Use a grid fine enough to find dead spots, often 20 ft or as specified by the AHJ, and include stairwells, elevators, basements, and locked rooms. Test with the building in normal condition and on all relevant talkgroups. For trunked systems, verify control channel and voice channel. Record worst-case results, not averages. Include the 12-hour battery load test, alarm reporting, and donor-site noise-floor check. Have the AHJ approve the method and witness or review the test before occupancy.
3. If the retest fails in several tenant spaces, what remediation and documentation should follow?
Read the worked answer
Remediate only the failed areas first: add or relocate antennas, adjust per-antenna power with couplers or attenuators, and correct any RF path problems. Do not simply raise global BDA gain, because that can overdrive passing areas and raise uplink noise. Re-test the failed spaces and adjacent areas after changes. Documentation should include the original failure locations, the design change, new RF calculations, and before/after DAQ and signal data. The final report must show 95% general-area coverage and 99% critical-area coverage at DAQ 3.0, plus battery and donor-network tests. The AHJ should receive the complete package before the certificate of occupancy is issued.