Storm-Damaged LTE Sector B
An LTE 1800 MHz three-sector site has a VSWR alarm on sector B after a storm. A drive test shows sector B RSRP of -112 dBm at 1.5 km, while the design prediction is -92 dBm; SINR is -3 dB. Sectors A and C are normal. The antenna has 4 degrees of electrical tilt and 0 degrees mechanical tilt. At the top of the tower, a jumper connector looks discoloured, but the tower is rated for climbing only when wind is below 35 km/h. Current wind is 30 km/h gusting 45 km/h, and daylight ends in two hours. The site has remote electrical tilt control and a ground-level VSWR test point. The operations centre wants the sector back on air before the evening busy hour.
1. Should the technician climb now? Justify with the safety constraints and immediate alternatives.
Read the worked answer
No. The tower is rated for climbing only below 35 km/h, and gusts are already 45 km/h; a gust can arrive without warning, so the limit is not a steady-wind average. Daylight ends in two hours, the permit expires at 16:00, and this is a live three-sector site. The immediate action is to keep the sector alarmed, or reduce power/remote tilt only if the operator authorises it, and to use ground-level and remote diagnostics: PA output, VSWR history, RET position, RSSI, and alarm timestamps. Do not send a climber up to meet the busy-hour target. Reschedule the climb for a calm window with a rescue plan, RF power-down, and permit extension. If coverage is safety-critical, use a temporary sector or adjacent-site tilt change rather than an unsafe climb.
2. What sequence distinguishes a wet jumper/feeder, a failed antenna, and external interference?
Read the worked answer
Start at the ground VSWR test point with the base-station transmit path isolated and use antenna/load substitution. A high VSWR that disappears when the antenna is replaced by a load points to the antenna; a high VSWR with the load points to the feeder or jumper. If available, use distance-to-fault or sweep to locate the discontinuity; a discoloured top jumper is consistent with water ingress but is not proof. If VSWR is normal, check PA output and receive RSSI. Low RSRP with normal VSWR suggests antenna gain/pattern, tilt, or feeder loss; low SINR with normal RSRP suggests interference or PCI/neighbour conflict. Compare sector B against A and C at the same test points, and use a spectrum scan for uplink interference. Replace only after the measurement isolates the section.
3. If VSWR is normal at ground but sector B coverage remains 20 dB low, what is your next decision?
Read the worked answer
Do not assume the antenna is bad. Verify the RET actually moved to the commanded 4 degrees and that the sector's power, gain, and neighbour list match design. Check whether the drive test used the same PCI and whether sector B is overshooting or blocked by new clutter. If remote data show normal VSWR and normal PA output but low RSRP, a receive-path or antenna-pattern fault is possible; schedule a climb to inspect antenna orientation, connector torque, and water path, and to run a sweep at the top. If SINR is the main problem, treat it as interference first: scan uplink, check PCI confusion, and adjust tilt or power only after identifying the source.