Three OB vans, one isolated bus — the broadcast remote at Music City Center.

Advance walk, four weeks out

The advance walk happened on 22 May, four weeks before show. We walked the south apron with Music City Center’s house electrician (Cheng Mai, IBEW 429 hand, ten years on the deck at MCC), with NEP’s remote engineer (Sebastián Cortez, lead engineer on NEP-RU14), and with the network’s remote producer (Lila Fontaine). We confirmed the four shore-power tie-ins at the apron — Cam-Lok Series E single-pole, 200 A per tap, served from the MCC switchgear room three flights below the apron level via a permanent 4/0 feeder pull.

Cheng pointed out an artifact of the building’s 2013 commissioning that mattered: the apron shore-power taps share a common neutral with the MCC kitchen exhaust hood circuits. Under normal operation the kitchen draws are quiet and the shared neutral is clean; under heavy convention catering load, however, the neutral can carry up to 35 A of imbalance current that would inject 60-Hz hum onto a downstream isolation transformer’s safety-ground reference. We made a note to verify the kitchen schedule on the day of and to take a baseline neutral-imbalance reading before energizing the iso transformers. (As of advance filing, the network is the only major event on the venue’s calendar that night, with no catering load.)

Single-point grounding — three trucks, three star points

Each of the three OB vans gets its own Powerstax 5-kVA isolation transformer at the apron, on a road case between the truck and the shore-power tap. The transformer’s XO point is the single bond to earth for that truck; the bond runs through a #6 stranded green-yellow EGC to a dedicated ground rod array driven beside the apron (three 8-foot copper-clad rods, equilateral 6-foot spacing, bonded through a Cadweld exothermic to the iso XO).

The audio iso bus for the in-hall capture uses the dual-bus Hammond C1F005CES — one 5-kVA bus for the network’s audio cap mic-pre rack, one 5-kVA bus for the venue’s in-house FOH bus. The two buses are independently grounded at independent star points, with the two ground references tied at the iso transformer’s input side. The in-hall capture lives forty feet from FOH on a road-case rack we wheeled in during advance setup.

Ground-loop audit

The ground-loop audit happens at 16:00 CDT on the day of, three hours before air. Procedure: with all three OB vans powered through their iso transformers but with no broadcast signal flowing, we clamp a Fluke 376 FC around the safety-ground conductor of each truck and read the 60-Hz current at the ground reference. A clean install reads less than 50 mA; we shoot for less than 25 mA and have seen single-digit readings on well-isolated remotes.

The advance simulation (with both my and Sebastián Cortez’s test rigs running on 22 May) gave us 12, 18, and 22 mA on the three trucks respectively — comfortably inside the action limit. We will re-run the audit at 16:00 CDT on the day of and document the readings in the daily log. If any reading exceeds 50 mA, we identify the secondary ground path (usually a satellite-uplink truck’s dish mast bonded to the apron’s reinforcement steel) and bond it through the iso transformer’s ground reference instead.

TVSS at every tie-in

Each shore-power tie-in gets an Eaton SPD3 series-mode TVSS module on the line side of the iso transformer. The SPD3 is rated 100 kA short-circuit at 480 V and carries a UL 1449 4th-edition Type 1 listing. We do not rely on the SPD3 for diversion of large surges to ground — series-mode TVSS works through impedance, not through ground-current shunting — but it does protect the iso transformer’s primary winding from line-side transients (typically utility switching events or nearby lightning). The 22 June forecast as of advance filing shows isolated afternoon thunderstorms; we’ll be tracking the Vaisala NLDN alerting service from T-180 to air.

UPS on the critical bus

Each OB van’s primary critical bus (video router, embedder, RF generator) rides through an APC Symmetra LX 8 kVA double-conversion UPS sized for 90 minutes of runtime at 50% load. The Symmetra is on the truck side of the iso transformer; the UPS sees regenerated 60.0 Hz at all times — no transfer event when shore power drops out, no frequency shift if the MCC service trips. We have run on UPS battery exactly once in our broadcast career (2022, the Ryman, a venue service transient on a country special, 18 minutes of battery time; no frame loss).

The hall side — audio capture

The in-hall stage-side audio capture is a four-mic-pre rack feeding the FOH desk and the network’s broadcast pickup. The pre-amps (UA 6176 + Apogee Symphony) are sensitive to ground-loop hum at the audio band; we put them on the audio iso bus’s clean output and route the FOH send through a Jensen JT-MB-D differential transformer at the network truck end. The transformer is wired with internal Faraday shield tied to the network truck’s clean ground; the result is a galvanic break between the venue’s audio reference and the broadcast truck’s, with no degradation of frequency response in the 20 Hz – 20 kHz band.

Credit card

• Production NAB Tour Tech Broadcast Remote · 22 Jun 2026
• Venue Music City Center · 201 Rep. John Lewis Way South
• OB van vendor NEP Group · trucks RU14, SS22, AV9
• Remote engineer (NEP) Sebastián Cortez (RU14 lead)
• Remote producer (network) Lila Fontaine
• House electrician (MCC) Cheng Mai (IBEW 429)
• Lead — Briley E. Singh-Hartley (ETCP EE-31742)
• Crew J. Ferraro
• AHJ Metro Codes & Building Safety