Troubleshooting dropouts and hits on set

Something is wrong on channel three. There are perhaps twenty plausible causes and roughly ninety seconds of goodwill available to find the right one. What follows is an order of operations rather than a list, because the order is what makes it fast.

First question: is it RF or is it audio?

Nearly all wasted troubleshooting time comes from chasing the wrong branch of this tree. Answer this before you touch anything.

The RF branch, in order of likelihood

1. Antennas. Position, height, orientation, spacing and whether something metal or human has arrived beside them since you rigged. Antennas lying in the bag, pressed against the operator, or shadowed by a newly parked truck account for an unreasonable share of all dropouts. Fix this before touching frequencies.
2. Transmitter antenna. Coiled, taped in a loop, run along a metal boning channel, tucked under a wet armpit or damaged at the strain relief. The transmitter's antenna is the most abused component in the entire signal path.
3. Batteries. Voltage under load, not the indicator's opinion at power-up. Marginal cells reduce transmitter output before they announce themselves, and the symptom is shortened range rather than a clean failure.
4. Body absorption and geometry. A human body is mostly water and blocks UHF effectively. If the fault appears when talent turns away, faces upstage, or sits down, the body is between the pack and the antennas. Move the pack, move the antenna, or add a second antenna position.
5. Distance and obstruction. Concrete, foil-backed insulation, elevator shafts, vehicle bodies, tank walls. Range in a corridor is not range in a field.
6. Cable and connectors. Long thin coax runs at UHF throw away real signal, and adapters stack losses. A fault confined to one antenna leg is a cable, a connector or an amp, not the air.
7. Diversity behaviour. Rapid switching means the two antennas are seeing very different things — the classic multipath signature. Moving one antenna a foot or reorienting it often solves what re-coordinating cannot.
8. Multipath nulls. Reflections arriving out of phase can cancel at a specific point in space. If a hit lands at the same mark on every single take, that is a null or an obstruction. Physics does not repeat by coincidence.
9. Interference and overload. Only now is it worth suspecting the spectrum: another department's new transmitter, a nearby broadcast site swamping the front end, or an intermod product from a set that was coordinated before someone added a channel. See why wireless drops out near a TV tower.
10. Coordination. If two of your own channels degrade together, or a fault appeared the moment a new pack was switched on, re-check the frequency set for intermodulation rather than moving one channel at random.

The audio branch

If RF level is rock solid and the sound is still wrong, the radio is doing its job and the fault is in front of it or behind it.

Cable and connector

The single most common failure in the whole kit. Flex the cable at the connector and at the strain relief while listening. Intermittent crackle that tracks the flex is a dead lav — retire it, do not put it back in the bag to trick someone next week.

Moisture

Sweat, rain, tears and stage blood. A capsule that fades, goes dull or spits after twenty minutes on a running actor is usually wet, not broken. Dry it, use a moisture-resistant mount, and carry spares for the day.

Mount and wardrobe

Rustle, thumps and rhythmic scrapes are mechanical, not electrical, and they track movement rather than position. They are solved with tape, mole skin, wardrobe cooperation and a different mounting point.

Gain structure

A transmitter driven into clipping sounds broken in a way that reads as a fault. Check input gain against the loudest thing the actor will do, not against the rehearsal mumble.

The receiver output

Level, impedance and the cable to the recorder. If one channel is wrong at the recorder but right at the receiver's own metering, the problem is downstream of the radio entirely.

Sixty-second triage

1. Look at RF level and diversity on the receiver at the moment of the fault. RF or audio? Everything follows from this.
2. Ask where talent was standing. Same place every time, or random?
3. Check battery voltage under load.
4. Look at the antennas. Has anything or anyone moved next to them since you rigged?
5. Swap the lav. Then swap the transmitter. One variable at a time.
6. Only then reach for the frequency plan — and if you move a channel, re-run coordination rather than hand-picking a hole.

Most of what makes this fast is knowing what was true before the problem started: the morning scan, the coordination list, the antenna positions you rigged. Diagnosis is mostly the art of noticing what changed, which is much easier when you wrote down the starting conditions. See scanning and walk-testing for the habits that make that possible.