Tech Focus: Bodypacks


Part 1: Transmitters Boost Use of Onfield Audio

Conflicting requirements for greater power and smaller size make their design a complex proposition

Onfield audio — wiring players, coaches, and officials for sound — has captured sports viewers’ imaginations like few other innovations in broadcasting in recent years. As broadcast sports heads toward the era of immersive sound, those who make the wireless systems that make onfield audio possible see that trend accelerating. In addition, as the next round of league collective-bargaining agreements come up for renewal, the benefits of onfield sound are being recognized in practice: the 2011 NFL CBA codified much of the onfield sound now considered a routine part of football, and the imminent MLB CBA may provide more freedom for sound on the diamond in the future. But there are still plenty of nuts and bolts to be considered.

Deeper Engagement
Although battery life and size are critical in transmitter design, Paul Johnson, CEO, Quantum5X, which pioneered onfield audio with its PlayerMic lines, says remote control of the devices is also part of that hierarchy of needs.

“The A1 might do a sound check before an event, but, by the time a venue fills up, the sound in the house will have changed, and there’s no way to reach the unit,” he explains. “Being able to remotely control it becomes important.”

Johnson describes how Fox Sports buried some of its transmitters in the outfield during the World Series; after one of the games, imminent rain compelled the grounds crew to pull a tarp over the field before the audio crew could reach the transmitters to change batteries. However, the crew was able to turn them off remotely and conserve enough power to get them through the next day’s game. Another example Johnson notes is the ability to change audio frequencies on the fly, as RF-challenged spaces in venues have to navigate denser RF environments.

Collectively, all the improvements in design and capability encourage greater use of transmitters, says Johnson. (Battery fires like those Samsung mobile phones have experienced are not a problem for professional-grade wireless systems, he assures.) Currently, MLB umpires and NHL referees use Q5X RefMics, and PlayerMics are deployed in the NBA, NHL, and MLS and by some NFL teams and a growing number of rugby teams. And mid-level colleges and even some high schools are beginning to show interest in onfield sound systems.

“It’s all about deeper fan engagement,” Johnson says. “Player audio is driving fans to players’ and teams’ websites and driving second-screen engagement. Immersive audio is only going to accelerate that.”

Size Still Matters; So Does Security
Size continues to be important in the bodypack category, but the trend toward ever smaller transmitters may be nearing a physical cut-off point: batteries simply can’t get much smaller and still deliver the game-long performance required. In addition, teams and leagues are demanding that bodypack transmitters be as robust as possible, creating design challenges for manufacturers.

Lectrosonics’ DBa transmitter offers AES encryption.

Lectrosonics’ DBa transmitter offers AES encryption.

“They get onfield, so it has to stand up to that and do so without sharp corners or anything that can catch or cut,” notes Karl Winkler, VP, sales, Lectrosonics, whose bodypacks have been used by the NFL and NHL and, starting this season, by several NBA teams (rented through Bexel) as well. “The units can’t get any smaller, really, so it’s a challenge meeting all of the requirements, especially in the current spectrum climate.”

He is referring to ongoing spectrum reallocation, which he says was behind development of a new IFB system that uses the VHF (174-216 MHz) part of the spectrum to free up more UHF bandwidth for broadcast audio.

“What’s happening is that we’re moving the comms audio into VHF in order to leave more room in the UHF range for what people will hear at home,” Winkler explains. “Spectrum loss is making us make better use of what will be left.”

Also of concern is a rising noise floor in wireless, brought about by more devices’ using the 700 MHz and WiFi sections of the RF spectrum in sports venues, collateral to earlier spectrum reallocation. That has been pushing up demand for more-powerful transmitters, in excess of 50 mW. The requirement for larger batteries conflicts with the demand for smaller units, complicating design.

In addition, demand is steadily increasing for more encrypted wireless devices, something Winkler attributes to the attention brought to headset hacking in the last two years.

“The NFL has been using encrypted communications for some time, but they’ve been looking at our new DBa series transmitters, which use 256-bit AES encryption,” he says. “They’re looking for more security. The NBA, too. At the same time, we’re getting requests for secure systems from more college football programs. Security has become a major point of conversation now.”

According to Bill Ostry, senior market development specialist, Shure, both encryption and a more crowded RF environment led to the development of the frequency-diversity technology used on its Axient series wireless systems.

“Teams and leagues are looking for security, and frequency coordinators are having a tougher time and are looking for rock-solid RF,” he explains. But, he adds, improved wireless systems enable audio to keep up with rapidly improving video for sports. “No matter how many channels of audio you’re broadcasting,” he stresses, “each of those individual channels has to have the highest level of audio quality possible.”

Part 2: A Look at the Leading Transmitters

The use of onfield audio — wiring players, coaches, and officials for sound — is accelerating, thanks in large part to improvements in the RF bodypack transmitters. Here’s a selection of some of the leading current models.

The AEW-T1000a UniPak bodypack transmitter features an LCD display, soft-touch controls, and field-replaceable helical and flexible-wire antennas. It has a four-pin locking connector and offers both low- and high-impedance inputs plus a bias connection, for use with dynamic and electret condenser microphones, as well as Hi-Z instrument pickups. Switchable RF power provides eight hours of battery life in the high (35-mW) setting and 10 hours in the low (10-mW) setting (two AA alkaline batteries). A three-position sliding control cover prevents accidental shut-off/channel-switching.


Quantum5X Systems
The RCAS (remote-control audio system), the control system behind the QT-5100 PlayerMic and QT-5100 RefMic sports transmitters, has been totally upgraded. The hardware features a new, more powerful 2.4-GHz radio transceiver used to communicate the remote-control commands and telemetry from the bodypack, for a significantly increased remote-control range. Software and firmware upgrades add new user functionality, including a 2.4-GHz spectrum scanner, the ability to change the 2.4-GHz channel, and additional companding modes for use with various receiver companding schemes. These are in addition to the existing remotely controlled functions of on/off, frequency, mute/live, mic gain, group commands, and RF transmit power (10-250 mW). Since the RCAS is RF based, transmitter settings can be changed through uniforms and over relatively long distances without interfering with the athletes or on-air talent.

Quantum5X QT5100 PlayerMic S

Quantum5X QT5100 PlayerMic S

The QT-5100 family of wideband remotely controlled transmitters are designed for sports applications and are frequency agile from 525 to 598 MHz with 3,000 selectable channels in 25-kHz steps. Currently, there are five models of the QT-5100: Incognito, AquaMic (waterproof), RefMic (with integrated non-popping audio mute switch), PlayerMic, and PlayerMic S. The QT-5100 PlayerMic S, the smallest remote-controlled PlayerMic to date, features a soft, tough, flexible polymer enclosure measuring 3 x 1.5 x 0.4 in. and a run time of 3.5 hours at a 50-mW RF transmit power setting.

The QT-300 series, an updated version of the QT-256 legacy product, is available in three models: BeltPack, PlayerMic, and AquaMic. All are tunable to 3,000 frequencies in 25-kHz steps between 525 MHz and 598 MHz. The output power is adjustable in preselected steps between 10 mW and 250 mW. Mic gain is adjustable as well. The standard QT-300 enclosure is milled from industrial-grade aluminum and is the size of two AA batteries. The QT-300 AquaMic is a fully waterproof transmitter. The QT-300 PlayerMic comes in a 4.3- x 1.5- x 0.4-in. flexible, sweat-proof polymer enclosure designed for player safety.

Every Q5X transmitter uses the latest lithium-ion battery technology to maintain a green environment while providing four to 15 hours of run time (depending on battery size and transmitter power) on a single charge.


Shure Axient AXT400 receiver

Shure Axient AXT400 receiver

The Axient system in Frequency Diversity mode uses two AXT100 bodypacks to deliver seamless audio while mitigating interference during mission-critical audio broadcasts. Unique to Axient, Frequency Diversity allows the referee-audio payload to be simultaneously transmitted on two independent RF links so that, if one carrier is compromised, the second RF carrier continues to deliver the content. Different from simply double-packing the referee, the AXT400 receiver manages all audio and provides a single feed to both the stadium and the broadcast trucks. When it’s combined with the WA662 in-line dual bodypack mute switch, on-field officials can easily mute their microphones connected to their AXT100’s. Broadcasters can operate in full confidence with the best possible protection against interference while providing clear audio from the referees throughout the game.

Announced in November, the Digital 6000 Series uses the same long-range mode and proprietary Sennheiser Digital Audio Codec as the top-of-the-range Digital 9000 wireless series. Comprising a two-channel receiver in two versions, a bodypack, a handheld transmitter, and a rack-mount 19-in. charging unit, the Digital 6000 Series will be available in March. The digital two-channel receiver works across a switching bandwidth of 244 MHz (470-714 MHz), which is covered by three transmitter versions (470-558 MHz, 550-638 MHz, and 630-718 MHz). For larger systems, up to eight receiver units can be daisy-chained without the need for an additional antenna splitter; the multichannel system will work with a single pair of antennas. System latency is 3 ms. The Digital 6000 features true-bit diversity, transmission-error correction, and additional intelligent error concealment. For data security, a feature that is particularly important for conference and corporate use, Digital 6000 features switchable AES 256 encryption.

Sennheiser Digital 6000 Series receiver

Sennheiser Digital 6000 Series receiver

The SK 9000 high-resolution, uncompressed digital wireless beltpack transmitter is compatible with three-pin Lemo connector lavaliere microphones. Its housing is die-cast magnesium to provide maximum robustness at very low weight. The user interface offers an icon-based menu structure, and the device features infrared synchronization with the receivers, as well as exchangeable energy packs with lithium-ion batteries. The SK9000 is compatible with the flagship EM 9046 digital wireless mainframe, which accommodates up to eight receiver channels.

The SK 5212-II ultra-compact bodypack uses one AA battery and provides transmission over a switching bandwidth of up to 184 MHz in 5-kHz steps. The SK 5212-II features switchable output power of 10/50 mW, plus a low-intermodulation power mode that increases the linear headroom of the amplifier, allowing users to squeeze more channels into a crowded RF environment. Other features include HiDyn Plus noise reduction, backlit LC display, adjustable audio sensitivity in 1-dB steps from –30 to +40 dB and a switchable low-cut filter. Its wide switching bandwidth matches Sennheiser’s EM 3732-II true-diversity receiver, but the SK5212-II is also compatible with all 3000 and 5000 series receivers.

The SK 2000 bodypack transmitter, part of the 2000 Series, offers up to 75 MHz of switching bandwidth in 25-kHz steps, frequency response of 25 to 20,000 Hz, plus full compatibility with Evolution wireless systems. The SK2000 offers selectable output power (10/30/50 mW) allowing users to increase power for longer transmission ranges or reduce power to squeeze more channels into a tight frequency range. For long-range applications, the SK 2000 XP (U.S. version) includes an additional 100-mW output power mode. An optional rechargeable battery pack can be charged right in the unit using the external charging contacts. Other features include 20 fixed frequency banks with up to 64 compatible presets each, six banks with 64 user-tunable channels, and a pilot-tone squelch for interference-free operation. The SK2000 is compatible with the 2000 Series’ EM2000 and EM2050 receivers, all Evolution wireless receivers, and the EM 3732-II diversity receiver (with HDX compander activated).

The compact WTU-2 metal bodypack solution for the RE-2 system is automatically compatible with the Telex RSB-2 mute switch for football applications. It features selectable RF output power and rechargeable–AA-battery operation with optional BH-200 charger. The unit is compatible with RSB-2 referee mute switch.

Made of high-impact ABS plastic, the BPU-2 is a compact bodypack transmitter for the RE-2 wireless system. Its single on/off switch also functions as a mute, and the TA4 microphone connector is compatible with any EV lapel and head-worn microphones, including the RE97Tx and RE97-2-Tx. Other features include a “cellphone” rotating belt clip and a smart battery.

The DBa digital encrypted beltpack transmitter features AES 256-bit CTR encryption, wideband tuning (470-698 MHz), a highly linear RF output stage for reduced intermodulation distortion and true 50-mW transmission RF power for excellent range and resistance to dropouts. Features include a multifunction switch that can be configured for mute or power, making the unit flexible, and 24-bit/48-kHz digital audio for pristine sound quality.

The SSM (Super Slight Micro) Digital Hybrid Wireless micro transmitter tunes across 76.8 MHz or three standard Lectrosonics frequency blocks, features settings at 25 or 50 mW RF power, and runs on a rechargeable lithium-ion battery. Measuring 2.52 x 1.48 x 0.57 in., the SSM weighs 2.3 oz. including battery. It responds to RM remote commands, compatible with the Lectro RM smartphone app. Frequency bands offered are A1 (470-537 MHz), B1 (537-614 MHz), C1 (614-691 MHz) and D1 (691-767 MHz, export only).

The SMV Series brings Lectrosonics’ Digital Hybrid Wireless technology to miniature transmitters in two configurations: the SMV for smallest size and the SMQV for longer battery life. Both units incorporate a servo bias input to accommodate a wide variety of electret lavaliere or head-worn microphones. Two bicolor LEDs indicate input levels for proper modulation. Each unit features a backlit LCD and a metal housing milled from billet stock for maximum durability. Both units offer RF power settings at 50, 100, and 250 mW. The SMV Series units respond to RM remote commands, are compatible with the Lectro RM smartphone app, and are offered with 256 synthesized UHF frequencies in 100-kHz steps in nine blocks, each covering a 25.6 MHz bandwidth.

The WM is a water-resistant transmitter with a membrane keypad and a specially designed water-resistant machined-aluminum housing. It offers 256 synthesized UHF frequencies in 100-kHz steps in nine blocks, each covering a 25.6 MHz bandwidth. Features include selectable RF power at 50, 100, and 250 mW; dual bicolor modulation LEDs for accurate gain adjustment; and a backlit LCD for ease of use. The WM is powered by two AA batteries, with internal switching power supplies providing constant voltages to the transmitter circuits from the beginning (1.5 V) to the end (0.85 V) of battery life. The WM responds to RM remote commands, compatible with the Lectro RM smartphone app, for hands-free setting changes.

The BTR-240 bodypack uses license-free 2.4-GHz technology and offers multi-level security and audio encryption, ClearScan channel selection, a choice of two independent or simultaneous audio channels, eight full-duplex beltpacks or a virtually unlimited number of half-duplex beltpacks, an easy-to-read LCD display, two-wire and four-wire wired intercom interfaces, XLR in/out for interfacing with general audio systems, auto-select for condenser or dynamic microphones, and wired or wireless TR-240 beltpack operation.

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