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Up and coming alternative/indie band Japanese Breakfast on stage at the Ohana Festival in Dana Point, CA. (Photo Credit: Ike Zimbel)

RF Notes From The Festival Circuit: Several Instructive Wireless Scenarios

While the author is seeing a trend towards greater knowledge of RF deployment on the stages and events he's been coordinating, there’s always room to up our game and learn more about the inner workings of wireless world.

As the lockdown eased up a few years ago, some of the first gigs I found myself doing were festivals of one size or another, ranging from small, one-stage, one-day events to medium-sized, two-stage, multi-day events with “A-List” acts like Ohana Festival and Boots n’ Hearts.

I like doing RF coordination for festivals because of the many opportunities I get to interact with a wide variety of techs, everyone from young people who are doing their first tour with the first band of the day, to grizzled veterans working for the headline acts. It’s through these interactions that I get a sense of the general level of RF knowledge that’s out there in the trenches.

In terms of my approach, I haven’t changed much since that was documented in a previous article, “Surfing the Airwaves,” in that I still try very hard to come up with unique frequencies for every act rather than re-using frequencies, and I still offer to program those frequencies to anyone who’s got plenty of other things to take care of in their daily routine.

Why unique frequencies? First, because it frees me from ever having to worry about anyone’s gear being turned on at the wrong moment. Second, when this approach does work, it means that the RF spectrum is the most crowded when the first act hits the stage and then just gets better and better (in other words, less congested) as the day wears on.

As for offering to program your RF for you, I’m always happy to make life easier for someone who’s on tour, as I know from experience how demanding that life is, and, it gives me a chance to look over the rig and spot any potential problems.

With the above in mind, here are some interactions that I’ve had while RF coordinating at festivals over the past couple of years.

Photo Credit: Ike Zimbel

Scenario One

One of those interactions was with a last-act-to-sound-check, first-act-of-the-day bands. As with many up-and-coming bands, they were using entry level in-ear monitor systems, in this case Shure PSM300s. I calculated frequencies for those and gave them to their monitor engineer to program.

This he did, and I moved on to some housekeeping that I wanted to do before we got the show rolling. I was surprised a few minutes later when the monitor engineer came to me and told me they were getting “interference” on one channel.

This was unusual, even though there could have been more than 30 other IEM transmitters on the air at that time. In any case, it was easier and faster to just give him another frequency than to do my usual routine of looking at the frequency in question with a spectrum analyzer to see what was going on.

So, I did, and when he came up to me again a few minutes later and said they were still having the same problem, I decided that I would have to investigate. I asked the ME whose mix was having the issue? The drummer. Spectrum analyzer in hand, I walked over to the drum riser… just in time to hear the drummer say, “Oooh, that’s where that noise in my ears is coming from!”

Here’s what “that” was: The drummer was also the playback person (a position I call “Spacebarista” because it usually involves hitting the space key on a computer to start or stop a track), and, rather than wearing his IEM pack, he was holding it in his hand – the same hand he was using to hit the space bar.

Whenever the pack came near the keyboard on the laptop, he would get a blast of RF noise in his ears because a) many digital devices, such as computers, can be a source of RF “hash,” and b) he was using the version of the PSM300 belt pack with the plastic enclosure, which has very little shielding against random RF noise like what was being generated by his laptop.

So, a note to up-and-coming bands: if you think you’re in any danger of actually making it and ending up on a festival stage some day, please spend the extra hundred bucks per pack and get the “Pro” version with the metal belt packs. You won’t regret it.

Photo Credit: Ike Zimbel

Scenario Two

On another occasion, with an act occupying a similar place in the line-up, I had assigned and programmed four frequencies for their Shure PSM900 kits. This time I did have time to look at their frequencies, on-air, which, I admit, is good practice when there may be so many other in-ear frequencies lit up.

I didn’t see any frequency issues (which would have consisted of other transmitters being too close to the ones assigned), but I did notice that one of the transmitters was a good 20 dB lower than the other three. And, of course, that was the one assigned to the artist.

I quickly moved the BNC connector from that mix to the only open port on his combiner, and the frequency matched the others for RF level. So, a bad port on the combiner was knocking the RF level on that mix way down. Fortunately, the open port was there because he was just using a whip antenna on the unit dedicated to his cue mix (a common practice).

When I explained that he had a “bad port” on his combiner, his response was “What’s a port?” This illustrates two points.

One, that for a large number of the touring monitor techs and engineers that are out there doing the daily grind, RF is a chore that they have to deal with but not necessarily one that they have a strong working knowledge of how it works (and is meant to work).

Two, the fact that he hadn’t flagged this issue, and had gotten through shows with it occurring, supports my contention in “The Real Problem With Wireless” that RF gear generally works too well in that you can often still get sound out of it when things aren’t quite right. For the record, a “port” on an antenna combiner refers to an input BNC and its associated circuitry. These can occasionally suffer component failures. The symptom of this is usually lower RF output on the affected mix.

Scenario Three

With yet another act, after I had programmed the band’s IEM transmitters, I noticed that their after-market four-channel IEM combiner had lost all four screws that hold the front panel to the chassis of the device, leaving the actual combiner adrift in the rack. I checked the road case the rack had come in for the missing screws, a common place to find them, but no luck.

I told the ME what was up and encouraged him to hit a hardware store that was just a few blocks away and get some new screws. At show time, I was pleased to see that he’d done just that, and the show came off smoothly.

Why do I care if your equipment is falling apart? Because to many people, in particular the general public, RF equipment doing bad things during a show is almost a meme, and I’m opposed to any RF issue affecting a show, regardless of whether it’s a hardware problem, or a frequency problem.

A recent example of the public’s take on RF: I was having my teeth cleaned, when on a break in the cleaning, the hygienist asked me what I do for a living. When I told her I took care of RF on major events, her response was “Wow, you must be on the edge of your seat the whole time, waiting for something to go wrong!” (My response was something on the order of “Hrrgggkk!” because by that point the war-on-plaque had resumed.) But no, I’m not that way, because my modus operandi is to make it work.

Photo Credit: Ike Zimbel

Scenario Four

One interaction that I had with a headline act was interesting. This act had one of the nicest RF set-ups I’ve yet encountered, with the entire stage networked back to the monitor position. I gave my list of frequencies to their monitor/RF tech, she entered them in her laptop, and with one command the whole stage was programmed, including the extensive backline world.

As is my habit, once everything was programmed, I took a walk through the backline area to see if any channels looked noisy. The very first rig I came to, three of the four channels were clean, but the fourth one was lit up like Christmas tree, with every LED on and the display flashing warnings.

Because the tech for that rig was in the process of setting up, I figured he probably just had two transmitters on that same frequency turned on and that he would figure it out in good time. Moving on, the rest of the backline (which ran the width of the stage) was fine. When I got back to the first rig, it was still showing the same condition, but it was early times, so I just made a note to keep an eye on that rig throughout the day.

Well, the next time I was back that way it was still lit up, but the crew had finished setting up and had gone back to the bus already, so I just resolved to keep an eye on it. Flash forward several hours and I noticed the guitar tech for that rig starting to get things lined up for their show. I went over and asked him “What’s going on with that last channel?”, pointing to the light show. His response: “Oh, we’re not using that today!”

I asked if he minded my looking to see what frequency that channel was set to and he said, “Sure, go ahead.” Well, it turned out that that channel was on a frequency that was either right on, or very close to, one of the in-ear frequencies and was getting crushed by the monitor transmits just a few feet away.

I asked if he was OK with me tuning that channel to an unused frequency, and he told me I’d need to check in with the RF tech. She was nearby, and when I asked her, her response was “Oh, we’re not using that today!” But, she allowed me to re-program that channel with a frequency that I knew wasn’t in their assignment. The channel immediately settled down and the warning messages stopped.

So, here’s my take on that situation: You’ve got two cars in your driveway, and when you come outside to run an errand, one of the cars is sitting there quietly but the other one is blasting its horn and all its lights in alarm mode – do you just get in the other car and drive away, saying “Oh, we’re not using that one today?!?”

And, here’s why the situation needed to be dealt with. In that particular four-channel receiver, there’s one RF input stage that feeds all four channels. Overdriving the RF front end puts it into a protective limiting mode (which is why the system wasn’t damaged even after eight to ten hours of continuous RF overload), but it also limits the RF levels going to the remaining three channels.

So, if you find yourself in that scenario, the best response is to either shift the frequency of the unused channel by a few hundred kilohertz until it’s not seeing the in-ear transmit, or letting that one channel scan for a new frequency. Note that the scanning approach doesn’t guarantee that the channel won’t land on a frequency that may be in use later by another act.

Scenario Five

On another event, I was summoned to the stage for an issue with the headliner’s in-ears. Were they working? Yes. Did they sound clean? Yes.

The issue? When the tech did a scan with his mic receivers it looked like “intermod” city on the graph in the accompanying coordination program.

I took a quick look at his antenna deployment, and sure enough, this was a simple case of the receive antennas getting crushed by the transmit antennas because they were too close together. In particular, one of the receives was a couple of feet behind one of the helical transmit antennas. It’s been my experience that helical type antennas can have a significant lobe of energy out the back, and that was going directly into the receive antenna. Separating the transmit and receive antennas by a few feet cleared up the situation.

I’ve pretty much given up on having anything to say about the notion of “two receive antennas on one stand so it’s quick to set-up and tear down,” because I have to admit that even though it’s not “best practice,” it works night after night. I still must stress that it does make a difference in performance if the IEM transmit antennas and the mic receive antennas are too close together.

I’m seeing a trend towards greater knowledge of RF deployment on the stages and events that I’ve been coordinating, but there’s always room for all of us to up our game and learn more about the inner workings of wireless and RF. I hope these articles help with that.

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