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RF FAQ: Working Effectively With Wireless Frequency Coordinators

With wireless system use growing and the spectrum shrinking, frequency coordinators at shows/events are increasingly common – here’s what to know about working with them for an optimum outcome.

As the use of wireless systems continues to grow and the available wireless spectrum continues to shrink, the need for someone to coordinate all of that wireless on any given event becomes greater. It’s why you’re increasingly likely to encounter a frequency coordinator on a show or tour.

With this in mind, and as a frequency coordinator, I’ve come up with a list of frequently asked questions about what I do.

What is a frequency coordinator?
A person (or team of people on a large event) who is responsible for making sure that all wireless systems in use are compatible and have been assigned unique, coordinated frequencies to prevent interference. This is done with a variety of tools, including spectrum analyzers and wireless frequency coordination programs such as IAS from Professional Wireless Systems.

Frequency coordinators are also tasked with the job of monitoring and tracking down any “rogue” wireless users and either getting them coordinated or shut down. For a backgrounder on frequency coordination and why we need it, check out my article, “Avoiding Intermod” (here).

I’ve got a festival date coming up, and I’m told there’s a frequency coordinator on it. What is needed from me?
A list of all RF gear that your act is using. This must include make, model, frequency band and quantity of each system in use, as well as where it gets used. So, the simple part is the main wireless mic and IEM systems, say 4 x Shure UHF-R, J-5 band (stage mics) and 8 x Shure PSM-900, G-7 band (IEMs).

After that, list all backline systems, with each listing including the musician’s name and/or application (i.e., guitar, bass, etc.), make/model of their systems, their position on stage, the frequency band each system occupies, and any other special notes.

Note that it usually isn’t necessary to list actual frequency ranges as long as the Band/Block info is correct (so “J-5” is sufficient as opposed to “J-5, 578-638 MHz”). Also, it’s important to note if you have any custom frequency banks; for example, one act I’ve worked with a number of times has some Sennheiser G3 systems in its backline that only tune from 534 to 558 MHz (I’ve never found out why).

In addition, note any mixed systems that tune differently from the norm, say Shure transmitters into Lectrosonics receivers (this is possible) or Sennheiser 2000 Series transmitters, which tune in 25 kHz steps into Sennheiser 3732-II receivers, which tune in 5 kHz steps. In each case, it’s the limitations that govern what the coordinator needs to know.

OK, so I’ve given the coordinator all of the above. What happens now?
The coordinator will provide a list of compatible frequencies to use with your systems. On really busy, RF-intensive events, there may also be a timeframe specified as to when transmitters can be turned on. For example, the band is on at 5 pm, so you may be asked to not to turn on your transmitters until 4 pm, and also to have them off by 6:15 pm. Important!

Also make sure the backline people turn off their transmitters at the end of your show. A guitar vault with 4 to 6 transmitters, still on, in close proximity to each other is a great little intermod generator, which is not something you want parked backstage while the next act is going on.

What if there are problems with some of my frequencies?
Let the coordinator know ASAP and he’ll find alternates. Sometimes your list will be provided with alternate frequencies already. If so, try to keep track of which ones are bad and which ones you’ve moved to, as the coordinator will need to know these things if further work is required.

What you should not do is go “off-roading” to try to find your own frequencies. Here’s a little anecdote to explain why: One time while working on an awards show, I gave the monitor engineer from an act his list of frequencies. He looked it over and said, grudgingly, “OK, I’ll put these in, to start, but I will scan around because I’ve been screwed before.” (And he did have a very nice set-up with mics and IEMs from the same manufacturer, linked with a good monitoring/coordination program.)

I let that ride and made a mental note to keep a close eye on his frequencies from my own monitoring set-up (I did, he didn’t change anything), but here’s why that would be a really bad idea.

Sure, he has a state-of the-art scanning set-up, but what I have is a list of 240 frequencies that are, or will be, in use. In particular, this includes at least 24 channels of intercom belt packs, which are almost without exception set in the “push-to-talk & transmit” mode—meaning that they are only transmitting when someone is talking.

Which means that the likelihood of his scan picking them up is almost nil, which means that his scan would appear to show some wide open real estate to move his systems to when in fact, he might park his front man’s mic channel on or near the floor director’s transmit frequency… in which case her intercom chat could come out the lead singer’s mic channel.

This is also why it’s never a good idea to go looking for new frequencies after you’ve been rehearsed and sound checked.

What can I do to be a good RF citizen on an event with a coordinator?
The biggest thing is not transmitting until your allotted time slot. This is relatively easy now that most systems have a “non-transmit” mode. Using that mode while setting up and tuning your gear is very helpful RF-wise, and has the advantage of letting you get more of your set-up done in advance (like checking the patch and input levels to your IEM transmitters).

It’s really important to be on top of this when powering up, so you don’t start what I call a “frequency stampede.” A frequency stampede occurs when “Tech A” turns on a piece of RF gear, causing a hit on “Tech B’s” RF gear, which in turn causes Tech B to search for a new frequency. Meanwhile, as they’re tuning, they step on “Tech C” or back on Tech A, who then wants new frequencies. Rinse and repeat.

I’m a backline tech for a major act and I hear we are going to have a frequency coordinator on our next tour. How will this affect me?
It’s important that absolutely everyone using RF is on board. In practice, the frequency coordinator will provide a list of frequencies to tune your systems to at each new venue, and will also be available to resolve any issues that arise. This should make your life a lot easier and let you concentrate on tuning instruments instead of tuning wireless systems.

The same thing applies to the monitor position and other backline folks as well. It’s been my experience that most people are really happy to have the wireless aspect of the gig off their plate. It’s a funny thing, but because I only do shows with an RF coordinator on them (either me or someone I’m working with), I’ve never witnessed the struggles that seem to be a daily occurrence for a lot of techs.

Which leads me to close with a conversation I’ve had with more than a few monitor engineers I’ve worked with.

Me: “How’s it going?”

ME: “Are you (expletive) kidding me? I’m having the best day of my life!”

Ike Zimbel has worked in pro audio for 35-plus years and runs Zimbel Audio Productions in Toronto.

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