Wireless microphones and instrument systems basics

A wireless mic lets the singer walk into the crowd for the last chorus, and a wireless guitar system ends the nightly cable dance. Both also give you a new way to lose audio in the middle of a song: a dropout, a burst of static, or a competing signal from the DJ's system next door. Wireless is reliable when it is set up properly, and the set-up is a handful of habits.

The parts

• Transmitter. In the mic handle, or a bodypack on the belt for a headset, a lavalier or an instrument.
• Receiver. At the mixer or on the pedalboard. Turns the radio signal back into audio.
• Antennas. On the receiver; the more visible they are to the transmitter, the better.
• Frequency. The radio channel the pair talks on. Getting this right is most of the job.

Frequency ranges, in general terms

Wireless systems live in a few bands, and which ones you may use, with or without a licence, depends on the country. The broad picture:

• UHF, roughly 470–700 MHz. The professional choice: good range, good sound, many channels. Parts of this band are shared with television broadcasting and, in many countries, require a licence or are restricted to certain sub-ranges. The rules have changed several times in the last decade as mobile networks took over parts of the spectrum, so a system bought second-hand may be on a range that is no longer legal where you play.
• Licence-free UHF pockets. Many countries set aside small ranges (in much of Europe around 863–865 MHz, for example) for licence-free use. They are free, popular and therefore crowded: a wedding venue may have the DJ, the officiant's headset and your two mics all in a 2 MHz slice.
• 2.4 GHz. The Wi-Fi band. Licence-free almost everywhere, digital, sounds fine, and shares the air with every phone and router in the building. Good for guitar systems and for small stages; less predictable in a hotel with 200 guests on Wi-Fi.
• 1.8–1.9 GHz and other digital bands. Available in some regions, often licence-free with limited channel counts.

The practical advice: buy systems sold for your country by a dealer who can tell you the licensing position, and check before touring abroad. Where a licence is required it is often inexpensive per year for a band, and the alternative is interference and, in principle, a fine. This is not legal advice; regulations differ and change.

Why it drops out

1. Two transmitters on the same or nearby frequencies. Yours and the DJ's, or your two mics set up on channels that interfere with each other.
2. Distance and obstacles. A bodypack behind a body, a receiver in a metal rack with the antennas folded, a singer 40 m away in the garden.
3. Multipath. Reflections off walls arrive slightly late and cancel the signal at certain spots. Diversity receivers (two antennas, the receiver picks the stronger) cure most of it; single-antenna budget systems do not.
4. Batteries. A pack at 20% may work at soundcheck and fail in the second set as the voltage sags.
5. Digital noise sources. LED walls, video screens, some lighting controllers and laptop chargers spray interference close to the stage.

The set-up routine

Ten minutes at every gig, before the soundcheck:

1. Scan. Use the receiver's scan function to find a clear frequency in the venue, then sync the transmitter to it. Do this after the DJ and any other wireless users have switched on, not before.
2. Coordinate your own. If you have several systems, use the receiver's group or "auto-set" mode so your channels are chosen to be compatible; picking frequencies by hand a few hundred kHz apart is how you get intermodulation whistles.
3. Antennas up and visible. Receivers on top of the rack or on a stand, antennas in a V, with a line of sight to the stage. Not inside a flight case, not behind the sub.
4. Distance from digital gear. Keep receivers at least a metre from LED lighting supplies and laptop chargers.
5. Walk test. With the mic open and the PA at a low level, walk the whole stage and the audience area, and note where it crackles. That is the boundary the singer does not cross.
6. Fresh batteries and a confirmed meter reading. Then leave the packs switched on; a pack switched off and on mid-set may lose its sync.

Batteries

Wireless is the biggest battery consumer in the band, and battery discipline decides its reliability:

• Fresh alkaline batteries in every transmitter before every gig, or fully charged rechargeables from a rotation that one person owns. Typical run time is 6–10 hours on alkaline, 4–7 on rechargeable AA; a long wedding day can exceed both, so change them at the meal break regardless.
• Keep 12 spare AA and 4 spare 9 V in the spares case; the full list is in cables, spares and redundancy.
• Some systems use proprietary rechargeable packs; carry one spare per system and a charger in the van.

One wired backup

Every wireless input has a wired fallback ready: a wired vocal mic on a stand beside the singer's position, a cable coiled on the guitarist's pedalboard. When wireless fails, the fallback takes ten seconds and the song continues. Bands without the fallback lose a song and a chunk of the room's confidence.

What to buy

• Vocal wireless: a diversity UHF handheld system on a legal range, 300–600 EUR for the entry professional tier, 700–1,200 EUR for the tier most touring function bands use. Below 250 EUR, expect dropouts and a limited channel count.
• Guitar and bass: digital 2.4 GHz systems from reputable makers, 150–400 EUR, work well on small stages; UHF bodypack systems for bigger stages or Wi-Fi-heavy venues.
• Headsets for singers who play: the mic capsule matters more than the wireless; budget for a good headset and a mid-range pack.
• Count channels. Two vocal mics, one guitar system, three in-ear transmitters is six frequencies to coordinate. Buy within one brand family so the group coordination features work together, and note that in-ear transmitters and mic receivers must not share frequencies; see in-ear monitors for bands.

Do this today

• Check what frequency range each of your systems uses and confirm it is legal where you play.
• Put "scan and walk test" on the soundcheck routine, as in soundcheck etiquette.
• Set up the wired backup as a permanent fixture of the stage plot.
• Write down every system's frequency after each gig for a month; you will see which venues are trouble.

Where expert.band helps

Each wireless system, its spare pack and its batteries are inventory lines in expert.band's gear list, with the frequency range and the licence status in the notes where every member can read them. The kit puts them on the gig checklist with an owner, and the "fresh batteries" line is a tick, not a memory.