Don’t Let Rehearsals Fool Your Wireless Microphone

Too often, we receive worried calls from techs or FOH engineers that go a little something like this: “We set up and coordinated our wireless during rehearsals on Tuesday, but on Sunday we had the worst dropouts! What’s going on?”

Usually, new variables absent during rehearsal have changed the shape and behavior of the radio environment, causing equipment to fail, even if settings are unchanged.

There is no practical way to replicate the RF environment of a full auditorium during an empty rehearsal.

There is, however, ample evidence for what can be expected to go wrong, so you can take steps to avoid it.

Higher noise floor

When 500 people and their cellphones pack into a building, security and staff power on two-way radios, and stage lights and LED walls turns on, the noise floor of the UHF band typically goes up, even if there aren’t any new wireless audio devices using UHF added to the mix.

Although an increased noise floor may not create dropouts on its own, it raises a mic or IEM’s general susceptibility to other sources of interference.

Technical Director Daniel Scotti and the team at Saddleback Church worked with us to illustrate just how much RF conditions can change between an empty room and a full one.

Here’s a frequency scan using an RF Explorer RackPRO and Clear Waves of Saddleback’s main sanctuary on a Saturday before services, with everything powered down.

And here it is on a Sunday, first during a pre-service run through with mics and IEMs powered on, and then during the actual service.

We scanned the entire UHF broadcast band, 470-698 MHz, so visually these results don’t look as dramatic as they might were we examining only a few MHz, but a significant difference is there. The noise floor rises once devices are powered on, and rises in some places again when the audience is present and service underway.

If frequency coordination was sloppy during rehearsal, its faults can rear up during the actual performance when there is less headroom between the signal of interest and noise.

Frequency coordination during rehearsals should follow best practices and use software programs like Clear Waves or PWS’ IAS to calculate intermodulation products to make frequencies as reliable as possible, rather than “good enough.” Techs should assume RF conditions on the day of the performance will be much worse than they are with an empty building.

Performances in urban areas should also consider the possibility that neighboring groups may also be using wireless audio equipment at the same time. Although wireless microphones are low power, they can still cause interference over short distances or between adjacent buildings.

Is there a concert scheduled for Saturday night at the club across the street? Is there another church also holding services on Sunday at 11:00 AM next door?

If so, consider reaching out to them to exchange frequency lists to ensure you won’t step on one another’s toes.

Line of sight

Wireless audio devices need an unobstructed path between the handheld or beltpack and the antenna back at the rack or remote antenna location. Radio waves are absorbed by human bodies. A human body in-between receive and transmit antennas is not good.

Although we see line-of-sight problems in all markets, it seems to be a big problem for houses of worship. Maybe because audience members do a lot of standing up and sitting down.

“Antennas are often set too low,” says Kent Margraves of WAVE, a top-notch integrator based out of North Carolina specializing in houses of worship, including Saddleback. “FOH guys don’t want to put antennas up on stands, but that’s a terrible mistake.”

External antennas are kept discreetly at eye level, just above the heads of seated audience members. As soon as the first rows in front of the FOH position get up, that clean line-of-sight signal gets snipped.

Saddleback was also kind enough to give us comparison scans for when the audience was seated vs when they were standing.

We’ve circled an area around 550-580 MHz where the physical changes caused by audience position dramatically attenuate received signal strength.

External antennas should be on stands well above the tallest audience member with a clear view of the stage. They can also be mounted anywhere within the facility that also provides line-of-sight—like on walls or ceilings—using long runs of low-loss coaxial cable or an RFoF system like the RF Optix.

“The best systems are not installed FOH at all,” continues Kent. “The receivers are backstage in a production rack and the antennas are flown beside or above stage.”

But we assume you’re using external antennas in the first place. Much worse than a low flying external is burying stock whip/dipole antennas in a closed rack housing, or scattering receivers around the booth.

Radio interference on or around the stage

Any kind of electronic device has the potential to create harmful radio interference. Most devices emit some kind of RFI, but the ones up on the stage are most likely to interfere with wireless audio equipment (especially IEM belt packs) because of their proximity, so the stage should be checked and checked again for culprits.

Bands carry all sorts of troublemakers with them everywhere they go. Amps, keyboards, pedals, effects processors, can all produce powerful interference, whether they are malfunctioning or not. If possible, choose frequencies when all the band’s equipment is powered up.

Kent suggests band members and anyone else allowed onstage be required to leave personal electronics in the greenroom. He also suggests vetting mixing equipment brought by the band for interference before letting it up onstage.

Want better wireless? Download our eBook on three essential concepts for correctly deploying and maintaining interference-free wireless audio systems.

Leading image courtesy Chris Fenton.

Journey to the Center Conductor

A few days back we got an email from an engineer in Spain about whether our RF Optix fiber optic remote antenna system is compatible with a so-called “leaky coax” system in an underground mining communications installation.

Just when I think I’ve heard about every sub-field this tiny industry has to offer, another, even more obscure one emerges.

Leaky coax though, also known as radiating coax, really isn’t that obscure—we just don’t hear much about it at RF Venue.

Radiating coax allows RF to go where RF shouldn’t go at all: in the depths of a mine, on subway platforms, freeway tunnels, military bunkers, aircraft carriers, nuclear reactors, and more.

“The purpose of ordinary coaxial cable is to contain radio waves inside the cable,” says Tony Fedor, a Product Manager of cable at Times Microwave Systems. “The purpose of radiating coax is to let it leak out. It’s like having a continuous antenna where antennas aren’t practical.”

When connected to a radio, the exposed inner conductor in a length of radiating coax works like one long antenna. The metal shielding is deliberately absent, or selectively perforated or shaped to allow RF signal out into the environment at very low powers, or, in receive applications, expose the conductor to energy. Cable is laid out wherever RF coverage is needed.

There are many different kinds of radiating coax. Some are designed for specific frequency ranges, others have different loss characteristics, or types of connectors. The figure below is of Times Microwave’s popular T-Rad line.

It’s a little hard to see, but the shielding is split lengthwise and peeled back, making a semicircular sheath around the center conductor.

Mine communications may be one of the largest and oldest markets, but radiating cable is useful anywhere antennas are difficult to install and radio waves have difficulty propagating.

Applications range from mundane to exotic.

New York City and other major metropolitan areas have miles and miles of the stuff lining subway platform and tunnel walls so police, emergency personnel, and construction workers can communicate with the world above.

Tony tells me how Times Microwave supplied cable to a group that installs and services nuclear reactors, so they can keep in touch with people walking around in hazard suits inside the facility. Two-way radios are useless without leaky coax because of thick radiation shielded walls and airlocks.

It’s also buried around top secret facilities and used a covert perimeter detection system. A sensitive electromagnetic field hovers around the cable. Anyone that passes through the field changes the capacitive yield of the system and is perceived by monitoring software hooked up to the line.

There are even applications in sports and entertainment.

“We’re working with a company that has RFID tags embedded in golf balls,” says Tony. “They have a driving range with coax down the length of it that allows golfers to know precisely how far their ball has gone. They set up driving contests, and other games.”

Though the principle behind radiating coax is an easy one, in practice designing radio systems that use leaky coax is difficult. The biggest challenges are loss of signal strength (it is leaking after all), and coupling loss from imperfect connections.

All sorts of powered distribution thingamabobs are in this literally dark corner of the wireless industry to get around the problem. Just search “leaky feeder amplified distribution system.”

I asked Tony whether there were expert leaky coax design engineers who might talk to me about their work.

“They tend to be very secretive about what they do, and reluctant to give up much information—I’ve tried,” he said. “They only describe leaky coax as a ‘black art.’”

Want better wireless? Download our eBook on three essential concepts for correctly deploying and maintaining interference-free wireless audio systems.

The Time to Get Licensed Is Now

With the 600 MHz auction knocking, it has never been more important for large-scale users of wireless audio devices to get a Part 74 license. Thanks to regulatory changes, publicly available resources, and a streamlined licensing service recently launched by our partner Professional Wireless Systems, getting a license is easier than ever.

It used to be that only those working in the broadcast and film industries could get one of these. Good news arrived last year when FCC broadened eligibility criteria to include professional sound companies and operators of large venues that routinely use 50 or more wireless microphones. Now, just about every wireless “power user” has access to licensed status.

Getting licensed allows more powerful transmitters (up to 250 mW) and priority registration on the TVBD white space database, which protects against interference from TVBDs.

But there is another seldom discussed benefit that is just as relevant.

“As an industry we need to be better represented in the FCC’s system,” says Cameron Stuckey, of Professional Wireless. “One of the reasons the 700 MHz range was taken back so abruptly was that when the FCC did their due diligence and examined the spectrum they found only a couple hundred licensed Part 74 users and said ‘great, this isn’t going to bother anyone.’”

Cameron explains that when it comes to voicing opinions on pending regulations, users who have a callsign have big advantages over those who don’t.

Anyone who buys a wireless microphone off the shelf is by default operating as a Part 15 or “unlicensed” user. Were such a user to submit a comment on a Commission item, from the perspective of the FCC they seem like “just an average citizen,” he says.

“It’s a totally different paradigm when you have 500 licensed users of the spectrum voicing the same opinion compared to 500 ordinary citizens trying to sway the FCC. If you file a comment and you have a callsign as a licensed user they are required to read through your comment and take it seriously in the debate.”

If you value your ability to operate lots of wireless post-auction, it behooves you to hop on the license train ASAP both for the technical and political benefits a license potentially provides.

You can apply for a license on your own, especially if you are a location sound mixer or broadcast professional. That path is well trodden and there is even a handy step-by-step guide prepared by IATSE 695 for those who want to go it alone.

But even those who do qualify and are aware of licensure have been hampered by the bureaucratic requirements of the application process, along with technical glitches that plague the FCC’s tragically outdated online software.

PWS spares organizations (for which the process is slightly different than the IATSE link above) from facing off with this notoriously difficult process.

“We have a true turnkey system for getting licensed,” explains Cameron. “There is a brief security form, just like if you were buying anything else, where you put in your name and mailing address and a few other details.”

PWS then handles the rest, and your license arrives a number of weeks or months later.

The service is offered at a flat rate of $600, which includes the FCC’s $160 filing fee. Contact PWS at FCClicensing@professionalwireless.com for more information.

Leading image courtesy Christopher Skor.

Just How Dead Is the Recording Industry?

While having dinner with a friend, Tony Falco, and his wife Liz, he mentioned that he is actively looking for a space to record. I rattled off a few pessimisms about the anemic state of the recording industry, and received a well-deserved eyebrow from Tony.

I have no personal or professional experience in, or aspirations to, recording. But I have heard about it.

Mostly, I hear bad things: that recording is “dead” or “dying,” wounded first by DAWs, and then killed off in 2008.

That’s why Tony’s plan surprised me. Why would you open a recording studio in this day and age, and actually expect to make any money from it? Tony, a drum performance graduate of the New England Conservatory of Music, is anything but naive about music careers.

It surprised me so much that I thought I would investigate my assumptions.

So, can you still make money opening and running an independent studio?

The first thing I did was give Tony a call to get his thoughts on paper. Why dream of opening a studio?

“If,” he told me, “you recently invested in physical gear and traditional education with the sole intent of becoming an audio engineer and opening a studio, the accessibility of software tools and an abundance of used gear probably did kill the dream in that respect.”

It’s old news that the introduction of affordable digital audio workstations like Pro Tools in the late 90s heralded the beginning of the end for old ways of making records, and the obliteration of many of the iconic big studios.

“For me,” continued Tony, “it’s not all about recording. A studio is just one of the pieces that fits together to make my life as a musician work. I’m making an investment in software, equipment, and space for what it would take to record a single album, and then I also have a space that separates my personal and professional lives where I can practice and teach.”

For many musicians and engineers like Tony, a studio is no longer a viable means of deriving the majority of an income, but can very easily be one of many different income streams in a way that was not possible before, because the equipment overhead is so much lower. Likewise, a specialized recording or mastering engineer who does nothing but record or master is now rare, while combinations of engineer/musician/entrepreneur/hobbyist proliferate.

When I asked Matt McArthur, Executive Director of Boston area non-profit studio The Record Company, on the possibility of running a profitable studio he promptly said, “absolutely, but it’s different than it used to be.”

“Because it is so difficult to derive a good margin—or any margin—from the sale of recorded material, the role of the recording studio has changed. It used to be the recording studio was something that artists and labels invested in on speculation that they would be able to produce a return on the product they created. While there are some successful artists in the world who still do sell records, for the most part making records is now a marketing expense.”

For his own enterprise, Matt applied a non-traditional business model—the non-profit—to a recording studio around a unique mission, to “amplify Boston’s diverse musical voices.”

The Record Company is a success because it approaches recording from a framework that acknowledges just how much the industry has changed. Like Tony, Matt is able to make recording financially “work” by fitting recording services in with other strategies. Their non-profit status allows them to accept donations, and they also rely on clients to provide their own freelance engineers, rather than keeping an in-house engineer.

Matt told me other studios have been able to survive as standalone, for-profit shops by doing the opposite: staffing a skilled engineer and maintaining margins by charging a premium hourly fee for his/her services either to professional musicians or, increasingly, to music hobbyists with disposable incomes.

There is even evidence that old-fashioned studios and studio roles have actually grown (albeit in small amounts) since 2004-05, fueled by the need for complex scoring sessions on sophisticated video games and big-budget television shows.

The US Census keeps records on industry employment information through the yearly Statistics of United States Businesses Survey. There is a lucky NAICS classification, #512240, that contains sound recording and mastering studios and almost nothing else.

Check out how precipitously employment dropped once DAWs became affordable.

But, the number of studios has steadily increased since then, and the ratio of small studios to large studios has grown.

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There is also this tantalizing chart that appears to show the incomes of sound recording studio employees steadily rising. In 2012 the payroll per employee was the highest it has been in more than a decade.

Because the SUSB survey for this code doesn’t tell us about every economic activity that involves sound recording and mastering, I can only say this information suggests the financial condition of existing recording studios isn’t getting any worse—which is still a much better prognosis than the stories of persistent deterioration and oblivion I’ve heard repeated by some.

We probably don’t get a good picture of the employment levels or incomes of freelance engineers who do not own their own studio. We don’t know to what extent musicians who are professional artists on paper are charging or paying for recording services under the table or as favors. And we can’t peer into the dark recesses of the hobbyist market.

And this last one, the hobbyist market, may be the biggest one of all.

Sparkling new pre-amps and rack processors show up at NAMM year after year. Someone’s buying them. Right?

“The lower end of the market, the base of the pyramid, has greatly expanded as the recording medium changed from tape machines to computer-based digital recording,” says EveAnna Manley, founder of Manley Laboratories, Inc. who helped me understand the new demographics of the end-user market for studio recording gear, which give a different perspective on the resilience of recording as a profession and pastime than the SUSB surveys do.

A few members of the RF Venue team witnessed these changing market dynamics while building Crowley & Tripp microphones.

Former Crowley & Tripp Product Manager and current RF Venue CEO Chris Regan commented, “overall, we saw the demand for the highest end studio gear ceding ground to the middle and lower end of the market. There is still a strong desire for quality tools to capture and record, they just don’t go into multi-million dollar facilities.”

Though C & T was as successful as any maker of ribbon microphones can hope to be, they watched as other high end gear manufacturers and retailers lost margins and went out of business.

So it’s great to hear manufacturers like Manley are doing well, even if many of their awesome tube amps vanish into garage and basement studios, never to be seen (or heard from) ever again.

“While we still supply recording gear to traditional recording and mastering studios, film scoring stages, live sound touring rigs, and working recording engineers,” EveAnna continued, “the market that has really opened up in the last decade or so has been to the songwriter and the hobbyist who have set up DAW-based recording rigs at home.”

How much has the hobbyist market expanded? And what percentage of all studio equipment manufactured do hobbyists buy?

The wireless audio market does not allow me to answer these questions, though it does let me sit at a desk in a city and blog.

As for Tony, he lives out in the sunny hills of Greenfield, steadily building a small but sustainable musical universe that includes a studio. I’d say he’s living the dream.

Want better wireless? Download our eBook on three essential concepts for correctly deploying and maintaining interference-free wireless audio systems.

Visualizing Directional and Nearfield Antennas in Central Park

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To compare the effects of two different types of antennas (and the effectiveness of the RF Spotlight at reducing sources of interference), we traveled to New York City in search of something most professionals avoid: crowded spectrum.

We brought a camera, a wireless mic, and some other equipment and camped around 59th and 6th, just inside Central Park.

A passive coax switch fed one RF Spotlight and one CP Beam to a spectrum analyzer. The switch and analyzer let us visualize and compare what a wireless microphone receiver would “see” if either of these two antennas were attached at this location.

With the CP Beam, the signals and noise floor within the antenna’s pattern are amplified (under normal circumstances, a good thing if pointed at mic transmitters). With the Spotlight, the noise floor melts away, leaving nothing but signal, loud and sweet.

The unique radiation pattern of the Spotlight creates a “bubble” (as we often say) of coverage that envelopes proximate transmitters while attenuating competing RF outside its boundaries, resulting in vastly improved signal-to-noise ratio.

What We Learned From Our 2015 Survey

Last week, we sent a survey to RF Venue customers and Audio Gloss subscribers. Nearly a thousand people responded—far more than we expected—with all kinds of interesting information on how wireless audio devices are being used in 2015.

We came away with a much better picture of our customers, and of wireless audio users as a whole. We want to share some of what we found with readers.

The survey went to audio and A/V professionals who work regularly with wireless microphones, or who have an interest in wireless audio products, including our dealer network, and other partners who have purchased RF Venue antennas and RF distribution equipment direct from the factory.

Our customers are over-represented by A/V dealers, wireless audio “power users,” broadcast professionals, and system integrators, so we also sent it to our diverse audience of blog subscribers, most of whom have never purchased from RF Venue.

The first surprise was the ubiquity of in-ear monitors. About 83% of respondents said they work with IEMs.

This confirmed what we already knew, that in-ears have grown more popular in recent years, but we didn’t realize just how popular. It wasn’t long ago that IEMs pretty much lived on major tours. Today, local bands, small to mid-sized churches, and even pubs and small venues are upgrading from wedges to in-ears, or going straight from no monitoring to in-ears. Churches have really helped drive growth in the IEM market with contemporary worship styles that put lots of musicians up on stage every week in concert-like environments.

Aside from general device usage, participants also chose which of six wireless audio brands (AKG, Audio Technica, Lectrosonics, Sennheiser, Shure, and “other”) they use most frequently. Then, we asked which specific models of both mics and IEMs they use within that brand. Most professionals work with, sell, or specify a variety of different models (not just one), so we allowed respondents to choose multiple models.

Analyzing the multiple choice picklist gave us a fascinating look at the mixture of wireless audio technologies in use by our sample, as of this publication.

Some models were far more common than others. Here are the two most popular models by manufacturer.

We also learned what percentage of our sample uses digital modulation and in what frequency band.

39% of all respondents said they use at least one model of digital wireless microphone, with big differences in digital use by band and by brand.

The vast majority of digital systems reported were UHF: 36% of all respondents chose a digital microphone operating in the UHF band (470-698 MHz), with ULX-D accounting for the lion’s share. Only 8% said they use 2.4 GHz band systems. Even fewer picked digital systems using DECT (1.9 GHz) and 900 MHz band frequencies, 7% and 3%, respectively (We did not include intercom manufacturers in this survey, which might have bumped the 2.4 GHz and 900 MHz numbers up).

While we learned what percentage of our sample uses digital microphones, we still don’t know exactly how many digital microphones are out there. In September of last year we conducted a small poll of five large A/V retailers and distributors on digital mic sales by volume. We asked each to roughly estimate what percentage of systems they sold was digital, and how many existing legacy systems they thought were digital. The ballpark estimate was that 25% of systems sold today were digital, and 2-10% of existing systems (which actually gets us pretty close to the number we uncovered last week, but far from hard numbers).

Likewise, there may not be a correlation between a particular microphone model and how many microphones of one model are used or sold by a respondent.

For example, of those who said they use or sell Shure, about 70% said they use the top of the line UHF-R, more than any other model. Only ~30% of respondents said they use the more economical SLX. Does that mean by volume UHF-R outsells SLX by more than 100%? Probably not across the entire market, but within the context of RF Venue customers and Audio Gloss subscribers, who are disproportionately represented by wireless power users, possibly…

But back to digital. 38% is the average rate across all respondents. If we drill down into respondents by manufacturer, the rates of digital adoption are quite different from manufacturer to manufacturer. Of those who use Shure as their primary brand, 68% use one or more digital models, but of those who use Lectrosonics as their primary brand, not a single respondent selected a digital model.

These percentages don’t necessarily mean that customers of one brand dislike the digital mics of that brand. They probably instead reflect the fact that some manufacturers have a lot more digital offerings than others. Shure offers a wide range of digitally modulated microphones, while Lectrosonics offers almost none.

Either way, we learned the wireless audio market is changing—fast—and that wireless audio users are diverse, adaptable, and intelligent.

Thanks to all who participated!

Want better wireless? Download our eBook on three essential concepts for correctly deploying and maintaining interference-free wireless audio systems.