RF FREQUENCY COORDINATION
Quick reference for wireless microphone frequency blocks, FCC restrictions, and intermodulation limits. Built for A1s and RF coordinators working corporate AV.
The 600 MHz Rule
Since July 2020, it is illegal to operate wireless microphones in the 617–653 MHz and 663–698 MHz ranges. These were auctioned to T-Mobile for 5G. Equipment that can even tune to these frequencies must be band-limited.
Shure Frequency Blocks
Axient Digital, ULX-D, QLX-D, SLX-D
| BAND | RANGE | STATUS |
|---|---|---|
| G50 | 470–534 MHz | SAFE |
| G57 | 470–616 MHz | SAFE |
| H50 | 534–598 MHz | SAFE |
| H54 | 520–636 MHz | CAUTION |
| J50A | 572–616 MHz | SAFE |
| K51 | 606–670 MHz | CAUTION |
| K53 | 606–698 MHz | RESTRICTED |
| L50 | 632–698 MHz | RESTRICTED |
Sennheiser Frequency Blocks
EW-D, EW-DX, Digital 6000
| BAND | RANGE | STATUS |
|---|---|---|
| Q1-6 | 470–526 MHz | SAFE |
| R1-6 | 520–576 MHz | SAFE |
| R4-9 | 552–608 MHz | SAFE |
| S1-7 | 606–662 MHz | CAUTION |
| S4-7 | 630–662 MHz | CAUTION |
Wisycom
MCR54, MTP60
Ultra-wideband tuning. Must avoid 617–653 MHz and 663–698 MHz. The wide tuning range makes Wisycom highly flexible for dodging local interference — but you still need to scan and coordinate.
Check Your City
Select a city to see which frequency blocks are recommended for that market.
Intermodulation & Channel Stacking
What Is Intermodulation?
When two or more wireless transmitters operate simultaneously, they create mathematical combinations of their frequencies called intermodulation (intermod) products. These phantom signals can land on the same frequency as one of your receivers, causing dropouts or interference. The more transmitters you add, the more intermod products are generated — exponentially.
Three transmitters generate up to 9 third-order intermod products. Every transmitter you add makes coordination exponentially harder. This is why you can't just pick frequencies manually — you need software like Shure Wireless Workbench or Sennheiser WSM to calculate intermod-free frequency sets.
Rules of Thumb: Channels Per Block
These are practical maximums in a single frequency block, assuming a clean RF environment and proper coordination software. Real-world counts depend on local TV stations, other wireless users, and venue conditions.
Best-in-class density. Requires Wireless Workbench coordination.
Standard mode supports fewer. HD mode packs channels tighter.
No High Density mode. Solid for small-to-mid corporate shows.
EW-DX uses a fixed 600 kHz raster. EW-D supports fewer.
Equidistant tuning grid. Designed for broadcast and theater.
Wideband tuning. Channel count depends on mode and bandwidth setting.
Legacy analog generates more intermod. Use coordination software.
The Real-World Rule
Manufacturer specs assume a clean environment. On a real show floor with neighboring events, DAS systems, and local TV stations, expect to use 50–70% of the theoretical maximum. For a 24-channel corporate show, plan on needing at least two clean frequency blocks. Always scan the venue before the show and bring a backup block.
Before the Show
Check the FCC White Space Database
The FCC maintains a database of which TV channels are active in every US market. Check it before every show to know which frequencies are occupied. Available at whitespaces.fcc.gov
Shure Wireless Workbench and Sennheiser WSM can query this data automatically.
Always Scan On Site
White space data tells you about TV stations, but not about other wireless users in the building. Hotel ballrooms, convention centers, and arenas often have DAS (Distributed Antenna Systems) and other events running wireless simultaneously.
Use your receiver's scan function or a dedicated RF scanner (RF Venue, Shure AXT600) to see what's actually in the air.
RF Coordination Is a Skill
List your RF coordination experience on Truss. Producers need A1s who can manage complex wireless environments.