Wireless Mic Frequency Coordination 101 (For People Who Aren't RF Engineers)

If you’ve spent any time online reading about wireless microphones, you’ve probably run into sentences like “ensure your intermod products do not fall within 250 kHz of the active carrier” and decided renting a DVD player from 2003 would be less stressful.

Good news: you do not need to understand any of that to run a successful show. Better news: when you rent from us, we handle all of it before the kit ships. This guide exists so you understand what’s happening under the hood, why it matters, and why you should care about it just enough to ask the right questions.

No jargon soup. No scare tactics. Just what you need to know.

What is frequency coordination, actually?

Every wireless microphone transmits audio as a radio signal on a specific frequency, measured in megahertz (MHz). Your pack sends signal on (say) 618.750 MHz. The receiver listens on 618.750 MHz, picks up the signal, and turns it back into audio for the board.

One mic on one frequency is easy. The problem starts when you have two mics. Or eight. Or sixteen.

Two radios on the same frequency fight each other. You get dropouts, bursts of noise, the dreaded “artifact wash” where audio comes through like it’s being chewed. So the obvious solution is to put each mic on a different frequency. And that works, up to a point.

The catch is that radio signals don’t live in neat little lanes. When you have multiple transmitters running at once, they generate extra signals at frequencies you didn’t intend — sums and differences of the frequencies you’re using. These are called intermodulation products, or “intermod” for short. If one of those intermod products lands on a frequency you’re also using for a microphone, you get interference that sounds exactly like two mics fighting, even though the frequencies you chose look fine on paper.

Frequency coordination is the process of picking a set of mic frequencies that don’t create intermod problems with each other and don’t collide with any other radio signals in the area. For 4 mics, this is annoying but doable by hand. For 16 mics, it requires software. For 40 mics in a downtown venue with local TV broadcasts nearby, it’s a full-time job.

Why you can’t just turn them all on and hope

The Shure and Sennheiser systems we ship have an auto-scan feature. You press a button, the receiver looks at the radio spectrum in the room, finds empty frequencies, and assigns them. For 1 or 2 channels in a quiet room, this works great.

For 4+ channels, auto-scan is not enough. Here’s why: auto-scan finds empty frequencies, but it doesn’t always check whether those frequencies will create intermod problems with each other when all the mics are turned on at once. You can scan, get eight clean frequencies, turn on all eight mics, and discover that channels 3 and 7 now sound broken because their intermod product landed on channel 5.

Coordination software (Shure Wireless Workbench, Sennheiser Wireless Systems Manager) runs the math ahead of time. It picks a set of frequencies that are mathematically guaranteed not to step on each other.

Every multi-channel MicKit we ship is pre-coordinated in our RF lab before it leaves the warehouse. The receivers arrive pre-tuned to a coordinated set. You turn them on, they sync to the packs, and they work. You do not need to run Wireless Workbench. You do not need to understand intermod. You just plug in.

What’s the G57 band and why do people say it?

The FCC divides UHF radio spectrum into bands identified by a letter or number. “G57” is Shure’s name for one of the spectrum slices that’s still legal for wireless microphone use in the United States — specifically, 470 to 510 MHz on some of their gear, though Shure uses letter-number band codes that map to different specific ranges depending on the product line.

What matters for you is this: when you buy or rent wireless mics, they’re designed for a specific slice of the radio spectrum. The band your kit uses has to be legal in the country you’re operating in, and it has to be reasonably clear of other users (TV broadcasts, cellular carriers, public safety radio) in your specific location.

Shure and Sennheiser both sell their wireless systems in multiple band versions, each tuned to a different frequency range. We stock the U.S. bands that are legal nationwide post-FCC-repack, and we pick the specific band for each kit based on where it’s shipping. You don’t have to specify “G57” or any other code when you order. We handle it.

What was the FCC repack, and should I care?

Between 2017 and 2020, the FCC reclaimed a chunk of the UHF spectrum that wireless microphones used to live in — specifically 614-698 MHz — and sold it to cellular carriers for 5G deployment. That’s the “600 MHz repack.”

The practical result: any wireless mic bought before 2018 that operates in the 614-698 MHz range is now illegal to operate in the United States. You probably have one sitting in a closet at your school. It might still turn on. It might still seem to work. You are not allowed to use it, and if you do, you’ll experience progressively worse interference as cellular carriers light up more 5G towers nearby.

Every mic we rent is post-repack gear, operating in legal, currently-available bands. If you’re renting, this is already taken care of. If you’re considering using some old PGX or EW100-era wireless your school still owns alongside a rented kit, stop. Retire the old gear. Run the full show on rental.

Shure and Sennheiser: not interchangeable for coordination

Here’s a subtle point that trips up people who know just enough to be dangerous. Shure wireless and Sennheiser wireless both operate in similar UHF bands. You might think you could rent a Shure kit and a Sennheiser kit, combine them for a show with more channels, and coordinate them together.

You technically can, but in practice, it’s a bad idea. The two manufacturers use different modulation schemes, different channel spacings, and different coordination software. Cross-coordinating is possible with professional tools and an experienced RF tech. It is not possible with auto-scan.

The clean answer: pick one brand and stick with it for any given show. Our kit pages let you toggle between Shure SLX-D+ and Sennheiser EW-D/EW-DX at the same price. Pick whichever you prefer, and if you need more channels than a single kit provides, we’ll send you a larger kit on the same brand rather than mixing.

What RentMicKits does automatically

Before your kit ships, we do the following in our RF lab:

1. Pull the most recent FCC and local-area TV broadcast data for your shipping address so we know what frequencies are in use where the kit is going
2. Run coordination software (Wireless Workbench for Shure, WSM for Sennheiser) against that data to pick a clean set of frequencies for your channel count
3. Pre-tune every receiver in the kit to the coordinated set
4. Sync every body pack and handheld to match
5. Label the packs with channel numbers so you know which goes on which actor
6. Test the full kit with all channels live simultaneously before packing it

When the case arrives at your venue, you open it, plug in the receivers, turn on the packs, and every channel is already coordinated. If you’re running multiple kits for a larger show, we coordinate them together across kits. This is the part of the service you’re paying for whether you realize it or not.

What you still need to do on your end

Coordination handles the radio side. It doesn’t handle everything. A few things are still your job:

Turn on the mics one at a time during soundcheck to confirm each pack is talking to its receiver and the audio is clean. This takes five minutes and catches any shipping-related weirdness.

Keep receivers and transmitters roughly line-of-sight when possible. UHF signals penetrate bodies and walls fine at normal theater distances, but if you park the receivers in a metal rack inside a concrete basement and your packs are 200 feet away through two walls, you’ll hit range issues. Put the receivers in the house, not in the basement.

Don’t turn on any additional wireless gear (walkie-talkies, wireless cameras, in-ear monitor packs) in the same UHF range as your mics without asking us first. Those devices were not part of our coordination, and they’ll step on your mics if they share frequencies.

Call us immediately if you experience unexplained dropouts or interference. We can re-coordinate remotely and push new frequencies to your receivers in a few minutes, and if the local spectrum has changed since we packed the kit (a new TV station, a temporary broadcast event), we can fix it before it ruins your show.

Plain-language glossary

• Frequency: The radio channel your mic broadcasts on, measured in MHz
• Band: A group of frequencies your hardware can tune to (e.g., “G57,” “Band A1”)
• Coordination: The process of picking non-conflicting frequencies for multiple mics
• Intermod: Ghost signals generated when multiple transmitters run at once, capable of interfering with your mics if they land on your active frequencies
• Repack: The 2017-2020 FCC action that took 614-698 MHz away from wireless mics and sold it to 5G carriers
• UHF: Ultra High Frequency, the radio range most pro wireless mics operate in

Frequently Asked Questions

Do I need to coordinate my wireless mics if I only have one or two? No. One or two mics in a normal venue will work with the receiver’s built-in auto-scan feature. Coordination matters most at 4+ channels and becomes essential at 8+.

Can your kit interfere with my school’s existing wireless mics? It can, if those mics operate in overlapping frequencies. This is why we recommend running a full show on rental gear rather than mixing old and new systems. Tell us what else is running in the same venue and we’ll coordinate around it.

What happens if a TV station turns on during my show? Unlikely but possible. TV broadcast schedules are predictable and baked into our coordination. If a new temporary broadcast event happens in your area (sports, politics, emergencies), call us and we’ll re-coordinate remotely.

Is the FCC going to repack the spectrum again? Not imminently. The current post-2020 legal ranges are stable for the foreseeable future. The wireless industry has lobbied hard to keep what’s left, and the current plan holds. We’ll update our gear if anything changes.

Can I run Shure and Sennheiser kits at the same venue on different shows? Yes. Different shows means different nights, and coordination is per-show. We’ve shipped a Shure kit for the musical and a Sennheiser kit for the spring concert to the same school more than once. Just don’t run both brands simultaneously in the same room.

Still confused? Don’t be.

You don’t need to understand any of this to rent successfully. You need to tell us the show, the venue, and the date. We handle the coordination. You open the case and run the mics.

Email hello@rentmickits.com with your show details, or browse kits and we’ll coordinate whatever you order before it ships. This is our job. We like doing it.