RF-Coordination

Four hundred channels and one piece of dirt: how festival RF coordinators actually do the math

Long-form, May 2026. Piece 1 of 3 in the RF coordination series. For working FOH, monitor, and system techs.

You walk a festival site at 8am the morning of doors. Nine stages. Three IFB rings for the broadcast crew. ENG getting B-roll on a golf cart. The headliner's monitor world wants four spare frequencies "just in case" because their guitar tech got burned on a UHF pop-up at a festival in Texas last summer. The trade-show vendor in the merch alley plugged in a wireless beltpack that nobody coordinated. Somebody on the artist bus is watching college football on a laptop using a WiFi extender that's blocking 2.4 wider than anyone realized.

Four hundred frequencies on the master plan. Probably four hundred and forty by lunch.

Most working FOH and monitor engineers will live through their entire career without seeing what the festival RF coordinator actually does on the morning of a major show. You see the result: clean channels, a frequency list slid across the table during patch, the name and number at the top of your scan that says "approved." You don't see the four weeks before that, or the eighteen tools, or the unspoken hierarchy that decides who got the freedom-of-the-cleanest-spectrum and who got the third-order intermod neighborhood. You don't see the math. You don't see why your scan looks the way it does.

This is a tutorial about what's behind the curtain. It's written for engineers who already know what coordination is, can use Wireless Workbench, and have done their share of show-day scanning. It's not a primer. It's the layer most touring rigs never get to see, plus the procedural discipline you can borrow from it even when you're not running a 400-channel rig.

We'll cover the spectrum reality you're working in (2026 edition), the tool stack the festival leads use, and what advancing actually looks like four to eight weeks out. Then the day-of procedure including the hierarchy nobody publishes, the math nobody shows you, what goes wrong on a festival day, and what you can take back to your own rig.

The spectrum reality you're working in (2026 edition)

The incentive auction closed on March 30, 2017. The FCC raised $19.8B selling off 617-652 MHz and 663-698 MHz to T-Mobile for 600 MHz LTE service. Wireless mics had to be out by July 13, 2020. That was nine years and five years ago, respectively. We're well past the part where this is news.

What's left for you in 2026, in rough order of how often you'll actually use it:

TV channels 2 through 36 (VHF and UHF below 608 MHz). This is most of the working band for production wireless. UHF in the 470-608 MHz range is where Shure Axient Digital, Sennheiser EW-DX, Lectrosonics Digital Hybrid, and most of the festival-grade rigs live. VHF (channels 7-13, 174-216 MHz) is having a quiet renaissance for IFB and lower-channel-count touring deployments because the band is uncongested in most markets and propagation is cooperative.

600 MHz duplex gap. Two slivers. 653-657 MHz is licensed (you need a Part 74 license, which most touring engineers don't have, but the festival coordinator's company often does). 657-663 MHz is unlicensed: 6 MHz available to anyone, which means it's also where the cellular-adjacent intermod traffic likes to land. Use it, but don't bet a critical channel on it at peak demand venues.

1.4 GHz (1435-1525 MHz, licensed). Higher-altitude band, gaining traction for digital systems where shop-grade tools can take advantage of the relatively clean spectrum. Licensing required.

944 MHz and adjacent (941.5-944, 944-952 MHz). Specific use cases: STL, broadcast remote, some production wireless. Less common in touring.

2.4 GHz and 5.8 GHz. What Shure GLXDplus, Audio-Technica System 10/20, and a chunk of the consumer-grade rigs live in. This is the band where the "convention center next door fired up its WiFi 6 access points" failure mode is a real failure mode. Not for your headliner's vocal mic. Often fine for guitar pedals on a club rig.

The thing nobody mentions in primers: the spectrum allocation isn't a static map. The Wireless Microphone Spectrum Alliance (WMSA) has been pushing the FCC for additional allocation specifically because Super Bowl 2026 broke deployment records and the 2026 FIFA World Cup and 2028 LA Olympics are both expected to land outside what current TV-UHF can support at peak. As of this writing, the negotiations are open. If WMSA succeeds, you'll see allocation changes within the next 24 months. If they don't, the festival coordinators handling those events will be running coordination jobs at scales nobody has tried before.

That last point matters for touring. Coordination isn't getting easier. The number of devices per square foot is going up, cellular density is going up, and the spectrum available isn't keeping pace. The procedural discipline that festival coordinators have built around 400-channel deployments is going to migrate down into rigs that today think a 16-channel coordination is "a lot."

International note for the touring engineers who cross borders: the US allocation isn't the global allocation. The UK has a different band plan, and Ofcom keeps a dedicated frequency coordination page for major events (Glastonbury runs its own coordination apparatus that bypasses standard application turnaround because demand is too high to handle piecemeal). Continental Europe runs CEPT bands. Japan, Australia, and Latin America all have their own carve-outs. If you advance a tour into a market you haven't worked, the first call is to the local rental house, not your stateside coordination tool. The math doesn't transfer.

The coordination tool stack

There are roughly three tiers of coordination software in working use. Each one solves a different problem. Mixing them up, using a shop-grade tool to plan a festival or vice versa, is one of the more common mistakes in deployment.

Shop tier (per-manufacturer): Shure Wireless Workbench (WWB), Sennheiser Wireless Systems Manager (WSM), Lectrosonics Wireless Designer. These are free, they're designed around their own ecosystem, and they're what every working tour with a single-vendor wireless rig should be running. WWB is the most-used by miles because Shure has the largest installed base in touring. WSM has gotten noticeably better with the EW-DX firmware push, and the new versions handle multi-system coordination cleanly when you stay inside the Sennheiser ecosystem. Wireless Designer is where the film and TV side lives because Lectrosonics' Digital Hybrid encryption story is what Hollywood wants.

Where shop-tier tools fall short: they assume their own gear. The moment you have a Shure ULX-D rig sharing spectrum with a Sennheiser EW-D IEM rig on the same site, plus a Lectro DPR plant mic for a sponsor segment, plus a Telex BTR-800 IFB ring, plus the venue's house Shure SLX-D for backup vocals, WWB sees half of it and ignores the rest. That's not WWB's fault. WWB was built to coordinate Shure stuff, which it does well. It's the wrong tool for cross-vendor festival planning.

Festival tier: Professional Wireless Systems' IAS (Intermodulation Analysis System) is the dominant tool at this level in North America. The pitch is that IAS holds a database of wireless equipment specs from every manufacturer and pairs it with current local TV frequency-use data, which lets a coordinator close out a 400-channel scenario in roughly ten minutes per pass and modify in the field. You don't buy IAS off the shelf. PWS sells coordination as a service. There's a Lectrosonics partnership that bundles trial IAS licenses with new wireless system purchases, which is the closest most working engineers get to the tool without hiring PWS for the gig.

Sound Devices SoundBase plus AstralComm is the new entrant. New as in 2026. It integrates the Astral wireless ecosystem directly into a coordination platform. Whether it grows into something that genuinely competes with IAS or stays a Sound Devices-friendly tool is the open question. Worth keeping an eye on if you're already in the Astral world for a film/TV broadcast workflow.

Independent / SDR tier: Nuts About Nets (RFCoordinator, Intermod Assist, IntermodAnalyzer). These target smaller-scale coordination using software-defined radio dongles like the RTL-SDR. They're cheap and they work for what they do. They're also what gets you about 80% of the way to a real scan for somewhere between zero and a few hundred dollars in hardware. For a small festival, a club tour with mixed wireless, a corporate AV person handling a 50-channel deployment, these are useful. They're not what's running Coachella.

The honest opinion in the margins: most touring rigs use the shop-tier tool that came with their wireless purchase, do the day-of scan with WWB or WSM, and call it coordination. That's coordination at the shop level. It's not coordination at the festival level. The difference is the festival level has cross-vendor visibility, current local TV data, an actual procedural pre-show pass, and someone whose job that day is the RF and only the RF. If your show has 24+ wireless channels, the day you decide you're tired of mid-show dropouts is the day you either learn to do the festival-level work yourself or you book the coordinator.

Pre-show: what advancing actually looks like

The first email goes out roughly six weeks before the festival. It goes to every touring act on the lineup, every sponsor activation, every broadcast partner, every ENG crew, every backline vendor, every comms vendor, and the venue itself. The subject line is some variant of "Wireless inventory request." The deadline is two weeks out. The compliance rate, in the coordinator's experience, is most of it on time. Another chunk dribbles in over the following week. The rest shows up on load-in day, when somebody plugs something in that wasn't on the form.

What the form asks for, at a minimum:

Manufacturer and model of every wireless transmitter you intend to operate on site
Frequency band the unit is capable of (e.g., G50: 470-512, K54: 606-630)
The current frequency tuned (often "TBD pending coordination," which is the right answer)
Whether the unit is a microphone, an IEM, an IFB, a comms unit, or "other"
Operator name and contact for day-of changes
Any units you'd prefer to leave dark (some artists travel with backup wireless they don't need on; coordinators want it inventoried anyway)

What working tours under-report, every single time: the IFB in the artist's ear during press. The wireless beltpack the lighting designer uses to talk to the spot ops because the venue comms doesn't reach the spot tower. The handheld the MC borrows for the sponsor mention between acts. The sound effects wireless the magician on the side stage uses to trigger the ceiling drop. Coordinators build a fudge factor into the master plan for these. The festival-experienced coordinators build a bigger fudge factor.

In parallel with the inventory drive, the coordinator runs a DTV scan for the venue's market. This part is widely misunderstood. A DTV scan tells you what licensed broadcasters are operating in the local TV bands on the day of the scan. It does not tell you what the spectrum will look like at showtime. Two reasons: cellular pop-up sites get installed for major events (every major sporting event and festival now triggers a temporary T-Mobile site upgrade in the area), and broadcast ENG vans roll in with their own wireless that wasn't there during your scan. The DTV scan is the floor of your interference picture, not the ceiling.

What the coordinator does with all this: builds a master frequency plan. This is the document that allocates specific frequencies to specific operators. It's not a single sheet. It's a tiered allocation: headliner mics first pick, headliner IEMs next, the broadcast feed coordination, sponsor segments, then the rest of the lineup in performance-time order. Each allocation gets exclusion zones around it (the third-order intermod products that any neighboring frequency will create with it), so the assignments cascade.

The plan goes through at least one revision before show day. The coordinator runs the proposed plan through IAS or equivalent, which checks for intermod conflicts at the third-order level and flags any frequencies that will produce products inside another assignment's exclusion zone. The coordinator iterates. By the time the plan is shipped to operators, every frequency is mathematically clean against every other frequency on the master plan, given the equipment inventoried.

Then somebody plugs something in that wasn't on the form, and the coordinator does it again on site.

The under-appreciated part of advancing is the relationship work. The coordinator who has been doing this for ten years has the cell numbers of every major touring monitor engineer's RF tech. When the inventory request goes unanswered for the third time, it's a phone call, not a follow-up email. Most of the time the unanswered email is an artist's tech being on a different leg of the tour and not having the festival-day inventory yet. A direct conversation gets the data. This is also why "we'll just have a coordinator on site that day" without advance work is the worst version of the job. Day-of without advance is firefighting.

The discipline you can borrow from the festival level even on a 24-channel touring rig: send the inventory request. Get the master plan to paper before load-in. Treat the day-of scan as a verification step, not the moment you find out what you're working with.

Day-of: scanning, allocating, and the unspoken hierarchy

The coordinator is on site by 6am on a festival show day. Earlier if it's a multi-day. The first hour is environmental scanning across every band the deployment touches, using whatever rig the coordinator's company favors (PWS uses their own gear; smaller coordinators use a combination of an RTL-SDR sweep and a calibrated walk-around with a handheld scanner). The output of this hour is a delta: what's in the air today that wasn't in last week's DTV scan. If a cellular pop-up site went up overnight, the coordinator finds it now.

The next two hours are reconciliation. The proposed master plan from advancing gets compared against the morning's environmental scan. Any frequency in the plan that's now sitting on top of new traffic gets reassigned. The reassignment cascades: moving one frequency can change the intermod picture for its neighbors, which means re-running IAS on the affected segment. By 9am, the operator-by-operator frequency list is in its final form for the day.

This is when the unspoken hierarchy shows up, because some operators got their first-pick frequencies and others didn't.

The hierarchy, roughly:

The headliner's monitor world (IEMs and stage wireless mics for the headlining act). Cleanest available spectrum, double redundancy on critical channels, exclusion zones generous.
The broadcast feed if there is one. Networks have contractual signal quality requirements that override most other considerations.
Other top-of-bill artist wireless, in performance order roughly.
Production comms (Clear-Com / RTS), IFB, A2 wireless. These tend to live in a different band so they don't compete directly.
Sponsor activations and trade-show floor wireless.
The supporting acts in reverse performance order.
The thing somebody plugged in at noon that wasn't on the form.

Nobody publishes this hierarchy. There's no contract that codifies it. It's how the work gets done because the failure mode of the headliner's IEM dropping out at 9:47pm in front of 80,000 people and a livestream costs the festival more than every supporting act's RF combined. Working tour techs who learn this hierarchy stop being surprised when their assigned frequency is the third-best option in the band. It's not a slight. It's the math.

How allocations get communicated: a printed sheet at the production office, an email blast to the inventoried contacts, and physical labels on every transmitter the coordinator's team has time to label. The serious shops will also push allocations directly to wireless systems that support remote configuration (Axient Digital, EW-DX with Control Cockpit, ULX-D over Dante) so that the operator just turns on a transmitter that's already set to the right frequency. That last bit is the future and it's not yet universal.

Then doors. The coordinator's job is now active monitoring. IAS or equivalent is running a continuous scan. Every channel has an RSSI history graph. The coordinator is watching for: unexpected occupied frequencies that weren't in the morning scan (someone fired up their wireless without checking), spectral degradation on a specific channel (an antenna issue, a battery issue, an operator turning their unit off and on at a bad moment), and pop-up RF (a brand activation that decided to add wireless during the show, a press event that wasn't on the master plan, a guest artist's tour bus showing up with an active wireless rig).

When something goes sideways during the show, the coordinator's recovery options are: retune to a pre-allocated backup frequency, swap to a redundant transmitter on a different frequency, or kill the offending source if it's not a paying party. The pros have rehearsed the swap. The amateurs are learning the swap in real time on the show that the rest of the year is going to be measured against.

The detail that working engineers don't always see: the coordinator is in radio comms with every monitor engineer and FOH engineer on the major stages throughout the show. Not for chat. For "we're seeing a hit on your channel 4, your operator's transmitter battery is at 12%, swap it now." That communication channel is part of the festival deployment and it's part of why the festival-grade work feels different from the touring-grade work. There's somebody whose job is the RF, in real time, with eyes on every channel. Most touring rigs don't have that resource. The closest substitute on a touring rig is the monitor engineer who has trained themselves to keep one screen on the wireless rack scan throughout the show. That's the borrowable discipline.

The math that nobody shows you

Intermodulation products are what you get when two or more transmitter signals interact in a non-linear element somewhere in the receive chain, typically the receiver's front-end amplifier. The result is a set of new frequencies that weren't transmitted by anyone but that the receiver hears anyway as if they were real signals. If one of those products lands on a frequency you've assigned to another wireless mic, that mic now has interference that isn't coming from anywhere obvious.

The basic intermod math for two transmitters at frequencies f1 and f2:

Second-order products: f1 + f2 and f1 - f2. These are usually outside your operating band and easy to filter.
Third-order products: 2f1 - f2 and 2f2 - f1. These land near f1 and f2 in the same band. These are the ones that ruin your day.
Fifth-order, seventh-order, ninth-order: progressively further out, progressively weaker, but with enough transmitters in the same room they pile up.

A worked example. Say you have three transmitters at:

f1 = 488.000 MHz
f2 = 491.500 MHz
f3 = 494.000 MHz

The third-order products from these three transmitters, considering pairs:

2(488) - 491.5 = 484.5 MHz
2(488) - 494 = 482 MHz
2(491.5) - 488 = 495 MHz
2(491.5) - 494 = 489 MHz
2(494) - 488 = 500 MHz
2(494) - 491.5 = 496.5 MHz

You also get the three-transmitter products: f1 + f2 - f3, f1 + f3 - f2, f2 + f3 - f1. Run those:

488 + 491.5 - 494 = 485.5 MHz
488 + 494 - 491.5 = 490.5 MHz
491.5 + 494 - 488 = 497.5 MHz

Three transmitters. Nine potential interference points to check, just at the third order.

Now scale that. With ten transmitters you have hundreds of third-order products to check. With 100 transmitters you have hundreds of thousands. With 400 transmitters you're at tens of millions of third-order intermod points to evaluate. This is what IAS and Wireless Workbench do for you in software. The often-cited Coachella number from a ProSoundWeb piece several years ago referenced 12 million intermod points evaluated for a single year's coordination at that festival; the current numbers at peak deployments are higher.

What "third-order product" actually means for you in practice: when you assign a frequency to a wireless mic, the frequency has to be clear of directly-occupied frequencies. It also has to be clear of the intermod products every other transmitter on site will produce. The exclusion zone around each assignment is the keep-out distance from those products. A frequency that looks clean on a spectrum analyzer can still be unusable if it's sitting on a third-order product from your own deployment.

The thing the math reveals that the basics don't: the most dangerous intermod products are usually inside your own rig, not coming from the venue. A 24-channel touring deployment that doesn't run intermod analysis creates its own interference sources. The exclusion zones aren't there to protect you from the world. They're there to protect you from yourself.

The tool side: WWB's intermod analyzer takes your inventory and produces a calculated set of assignable frequencies that are all clean against each other and against the configured environment. It's deterministic. Same inputs produce same outputs. The difference between a competent shop-tier coordination and a competent festival-tier coordination isn't the math; the math is the math. The difference is the input data: what's in the environment, what equipment is actually on site, what frequencies are the other coordinators on the same site using. Festival-tier inputs are richer. Output of the math, given identical inputs, is the same.

The argument for actually learning this: every touring monitor engineer running 16+ channels of wireless should be able to walk through the third-order math on a napkin. Not because you'll be calculating intermod products by hand on the show day. Because when WWB tells you the coordination has no clean assignment for channel 7 in your preferred band, the engineer who understands why is the engineer who can solve the problem. The engineer who treats the software output as a black box can only restart the software.

What goes wrong, and how the pros recover

Five failure modes that occur, in some combination, on most major festival days:

The pop-up cellular site. A T-Mobile crew shows up overnight and brings a temporary 600 MHz LTE site online to handle the load on the day of the event. The 600 MHz duplex gap allocations you'd built around in advancing now have a 50 dBm transmitter sitting next to them. Recovery: every channel in the duplex gap moves to a backup frequency in TV-UHF, intermod gets re-run, operators are notified during morning meeting. This is why the master plan pre-allocates a backup frequency for every primary.

The rogue wireless on the artist bus or in the activation tent. Somebody fires up a wireless beltpack at 11am that wasn't on the inventory. The coordinator's continuous scan sees it within minutes. The pursuit: walk to the location, find the operator, get the frequency moved to a coordinated assignment or get the unit shut off. The escalation if needed: production manager, then security. The "I'm just using it for a quick podcast interview" claim does not get the unit a free pass.

The undisclosed IFB. A broadcast partner brings a four-person interview crew with their own IFB ring that the festival coordinator never saw because the broadcast paperwork went to the festival's broadcast liaison instead of the wireless coordinator. The IFB ring is sitting on a frequency that's now causing intermod with the headliner's monitor channel. Recovery: late-stage coordination with the broadcast crew, often involving the broadcast crew swapping to one of the coordinator's pre-allocated emergency frequencies. The structural fix is to make sure broadcast paperwork always copies the wireless coordinator. The structural fix takes years.

The piece of gear that's developing a problem. A specific transmitter starts producing spurious emissions outside its assigned frequency because a power amplifier stage is failing or an antenna connection is intermittent. The continuous scan sees the spurious. The coordinator pages the operator. The operator swaps to a redundant transmitter. The failed unit goes to the rental house RMA queue.

The neighbor festival. Two festivals running simultaneously within RF range of each other (more common than people realize on a busy summer weekend in some markets). The other festival's coordinator is also coordinating, and the two coordinators talk to each other in advance. The two coordinators sometimes do not talk to each other in advance, in which case both are coordinating against an environment they think is theirs and isn't. Recovery: inter-coordinator communication, mutual respect for the other deployment, sometimes a small accommodation in the master plan to avoid a known frequency the other side is using.

What's in the recovery toolkit, in order of how often it gets used:

Pre-allocated backup frequencies on every critical channel
Redundant transmitters pre-configured to backup frequencies
The cell phone numbers of every other major coordinator working in the region
A small bag of replacement antennas (paddles, helicals, omnis) to swap into a problematic position
A handheld scanner for walk-around verification when the primary scan is showing something the coordinator can't explain
Coffee

The pattern across all five failure modes: the recovery happens fast because the preparation made it possible. The pre-allocated backups, the rehearsed swap procedure, the comms channels with the operators, the inventoried equipment with known characteristics. The festival rig that doesn't have those isn't a coordinated rig; it's a hopeful rig.

What you can take back to your own rig

You're not coordinating 400 channels. You're probably coordinating somewhere between 12 and 60. The festival-level work is overkill for your deployment and the festival-level price tag is not in your budget. None of that means the discipline doesn't apply.

The borrowable habits, in order of payoff per hour invested:

Inventory in advance, not on the bus. Before each leg of a tour, get the wireless inventory in writing from every vendor and act you're working with. Production company backline, opener's wireless, sponsor segment if any. Two weeks ahead. Treat "we'll figure it out at the venue" as a sign that something is going to break later.

Run the intermod analysis on your own rig before the season. Open WWB or WSM, plug in your full deployment as configured, and produce a master frequency plan with backups for every primary. Same plan in every market, adjusted only for the local environment via the day-of scan. The plan-once-then-verify model is faster than the design-fresh-every-day model and it surfaces the impossible coordinations before you hit a venue where they matter.

Pre-allocate backup frequencies. Every critical channel (vocal, headliner IEM mix, click track wireless if any) should have a pre-tested backup frequency that's also clean against the rest of your deployment. Test the backup at soundcheck. The operator should know which knob position is the backup. The backup should not be a thing you figure out at 9:43pm.

Treat the day-of scan as verification, not creation. Walk into every venue with your master plan in hand. Run WWB's environment scan. Compare against your plan. The scan tells you "your primary on channel 4 is now occupied; switch to backup." The scan does not tell you "design a new plan from scratch." The pre-work is what makes the day-of scan a five-minute task instead of a two-hour task.

Build the comms channel with your own RF tech, even if your RF tech is you. During the show, somebody is watching the wireless rack scan. Ideally that's a dedicated tech. On a smaller rig, that's the monitor engineer with a single screen open to the scan. The point is somebody is watching. The reason festival coordination feels different from shop coordination is that festival deployments have someone whose job is the RF in real time. The closest you can get on a touring rig is to make the RF view a permanent fixture in your monitor world, not a thing you check when something has already gone wrong.

The festival coordinators are doing more sophisticated work than your tour requires. They're not doing different work. The procedures scale.

Run a clean show.

— Above the Fader

Sources: