Tech Focus: Wireless Bodypack Transmitters

By Dan Daley, Audio Editor, Sports Video Group

“Better, faster, cheaper — pick two.” That nostrum of technology has proved valid for most verticals in the digital era but not for wireless audio.

“It has to work every time without fail, it has to be high-performance, it has to be affordable, it has to be flexible, it has to be smaller yet even more powerful and with even more features. People expect a lot from wireless systems,” observes Karl Winkler, director of business development, Lectrosonics. That has become even harder to accomplish as the wireless industry faces the second major loss of key RF spectrum in a decade, in the form of an FCC-mandated auction of the 600 MHz band scheduled for 2016. It means that wireless-bodypack manufacturers have to fight on multiple fronts to stay both viable and competitive.

Winkler notes the innovations that his company has had to develop to address market demands. In the face of spectrum loss, Lectrosonics offers bodypacks in three distinct frequency ranges, most out of the 600 MHz band; where the frequency does enter that zone, the device has the capability of locating guard-band and mid-band gaps automatically.

The company’s newest bodypack, the LT, has a multifunction switch that can be a mute button, power switch, or talkback button, depending on the need and the situation. Longer antennas are also thinner, minimizing physical interference with athletes. Power capability of up to 250 mW also includes a circulator/isolator to prevent intermodulation with nearby transmitters, an issue that becomes a bigger problem as RF-spectrum loss pushes noise floors higher.

(Some broadcast users are also asking whether it would be viable down into the VHF range, between 174 and 216 MHz. That would require even longer antennas, which would make them unusable for wireless bodypacks’ other major constituent: theatrical productions.)

Glenn Sanders, president of Zaxcomm, whose bodypacks are used by NFL and NBA teams, says the specter of spectrum loss prompted redesign of the company’s TRX and QRX product lines to widen their bandwidth to between 512 and 600 MHz, offering users more range below 600 MHz while still being ready for the carve-outs, such as guard bands and mid bands, in that piece of spectrum after the auction. The bandwidth range can also be adjusted by the factory, if necessary, for a fee. “We’re trying to keep it as flexible as possible so that not everyone has to run out and buy all new equipment,” he says.

Zaxcomm has also integrated a recording system, using a chip and a micro-SD card, into its bodypack. According to Sanders, sports users find that feature useful for gathering audio where microphones can’t go, and that has been finding its way into postproduction of sports-broadcast packages. A more recent new feature is NeverClip, a patented process for extending the microphone’s dynamic range to 126 dB without significant clipping and without the distortion that processed limiting can induce. “We’re all trying to adapt our products to what’s going on with spectrum,” he notes, adding, “But, at the same time, we have to also keep coming up with ways to differentiate our products.”

Interestingly, the high level of demand for this type of product has kept the number of manufacturers in that sector very steady, with little more than a half dozen able to meet the rigorous requirements of broadcast and theatrical users, the two biggest customer segments. Instead of the Asian competition that other pro-audio sectors have experienced, top-tier wireless manufacturers often find Asian markets their biggest customers. Winkler says his biggest sales have been to Japan.

Costs to Vendors
Spectrum reallocation is also going to cost vendors of bodypacks and related wireless services more money. Michael Mason, president of CP Communications, has seen the cost of wages and time spent on frequency coordination increase as available spectrum is reduced, and he expects that to continue. “The demand for more [wireless] audio in sports, especially on the field, is huge, and it’s driving the need for more frequency-coordination efforts,” he says. “It gets more difficult to use wireless every year, week to week. It means we have to hire more people to do coordination.”

He notes that wireless assets are already spread thin in broadcast sports, given the demand for more sound from more sources. That was underscored by a snowstorm that blanketed the Midwest and Northeast with several feet of snow in November and caused relocation of an NFL game from Buffalo to Detroit and an ensuing scramble to get wireless assets repositioned. “At the same time,” he adds, “we had another remote unit heading to New England that almost didn’t make it due to weather.”

The wireless assets allocated for each game are specific to the conditions at each game’s location: available frequencies and channels, overall RF density, types of equipment on each truck. Changing them at the last minute is extremely challenging, if not impossible, depending on the circumstances, says Mason.

At a time when sports viewers are demanding more on-field audio than ever, wireless bodypacks — the gateway to collecting that sound — are facing their biggest technical and economic challenges ever. This playbook is still being written.

Rounding out a look at RF bodypack audio transmitters, here’s a selection of some 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, a bias connection for use with dynamic and electret condenser microphones, and Hi-Z instrument pickups. Switchable RF power provides eight hours of battery (2 AA alkaline) life in the high (35-mW) setting and 10 hours in the low (10-mW) setting. A three-position sliding control cover prevents accidental shut-off/channel-switching.

The WTU-2 compact metal bodypack solution for the company’s RE-2 system is automatically compatible with the Telex RSB-2 mute switch for football applications and 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. The 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 LT beltpack transmitter tunes across 75 MHz or three standard Lectrosonics frequency blocks, features power settings at 50 and 100 mW, and runs on two AA batteries. A multifunction programmable switch on the top of the unit can be used for power on/off, mute, or talkback when used with Venue or SR series receivers. The LT responds to RM remote commands, compatible with the Lectro RM smartphone app. Frequency bands offered are A1 (470-537 MHz), B1 (537-614 MHz), and C1 (614-691 MHz).

The SMV Series brings Lectrosonics’ Digital Hybrid Wireless technology to miniature transmitters in two configurations: the SMV for smaller 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. They feature two bicolor LEDs for adjusting input levels for proper modulation, backlit LCDs, and metal housings milled from billet stock for maximum toughness with precision. Both units offer RF power settings at 50, 100, and 250 mW. The SMV Series units respond to RM remote commands, 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 water-resistant transmitter features a membrane keypad and a specially designed 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 in any environment. 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 QT-256, the world’s smallest analog transmitter, is used by a variety of professional sports leagues and teams, including MLB, NFL, NHL, soccer, and rugby. The devices offer 256 channels, manually adjustable in 100-kHz steps with an available frequency range between 600 and 698 MHz and an output power ranging from 30 to 200 mW. The standard QT-256 enclosure is milled from industrial-grade aluminum and is the size of two AA batteries. The QT-256 AquaMic, a fully water-proof transmitter offers the same RF profile as the QT-256 and can be used in such sports as surfing, kite boarding, and yachting and whenever a transmitter would be exposed to extreme wet conditions.

The QT-1000 PlayerMic offers the same RF profile as the QT-256 but comes in a flexible, sweat-proof polymer enclosure measuring 4.3 x 1.5 x 0.4 in. It has an internal antenna and is offered with a detachable or hard-wired lavaliere microphone.

The QT-5100 RemoteMic features a new design that is 30% smaller than Quantum5X’s previous version. It is 3 x 1.5 x 0.3 in. with a soft, tough polymer enclosure whose flexibility minimizes risk and discomfort to the talent. The output-power range is adjustable between 30 and 150 mW. With 4,000 channels available in 25-kHz spacing and a frequency range of 525-698 MHz, options for frequency management are greatly expanded. An enhanced companding solution enables use of a wide array of microphone elements.

The RemoteMic also incorporates the RCAS Remote Control Audio System, which enables remote operation of Q5X’s remote-enabled transmitters. Functions include on/off, RF frequency, RF power, mic gain, groupings, and monitor transmitter RSSI status and battery level. A laptop or the Q5X-QG-H1 handheld controller can be used to manage transmitters. Talent can be set up and adjusted on the fly.

Every Q5X transmitter leverages the latest lithium-ion battery technology, providing six to 12 hours (depending on battery size and transmitter power) on a single charge.

The BTR-240 bodypack uses license-free 2.4 GHz technology and offers multilevel 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 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.

The SK 9000 high-resolution, fully uncompressed digital wireless beltpack transmitter is compatible to three-pin–Lemo–connector lavaliere microphones. Instruments with line signal and guitars benefit from the cable-like audio transmission. The housing is made of diecast magnesium to offer maximum robustness at a very low weight. The user interface features an icon-based menu structure and infrared synchronization with the receiver. Exchangeable energy packs with environment-friendly lithium-ion technology supply the required energy while saving thousands of batteries over time. The SK 9000 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 offers transmission over a switching bandwidth of up to 184 MHz in 5-kHz steps. It 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. The wide switching bandwidth of the SK 5212-II matches Sennheiser’s EM 3732-II true-diversity receiver but is also compatible with all 3000 and 5000 series receivers.

The SK 250 beltpack transmitter offers a maximum 250-mW RF output power, quick-exchange battery or rechargeable pack, 16 switchable frequencies, and HiDyn Plus noise reduction. The SK 250 is compatible with the EK 3241 slot-mount diversity receiver as well as 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 SK 2000 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 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 SK 2000 is compatible with the 2000 Series EM 2000 and EM 2050 receivers, all Evolution Wireless receivers, and the EM 3732-II diversity receiver (with HDX compander activated).

The digital wireless QLX-D delivers transparent 24-bit transparent audio quality with outstanding spectrum efficiency and signal stability. It features rugged, metal handheld and bodypack transmitters with a half-rack receiver. It offers a feature set including AES256 encryption, IP networking for use with Wireless Workbench 6 software, ShurePlus Channels mobile app for iOS and AMX/Crestron devices, and the option to use Shure’s intelligent rechargeable-battery technology. QLX-D features many of the benefits of Shure’s high-tier ULX-D line, including its audio quality. Meanwhile, ULX-D enjoys more RF flexibility with high-density mode and higher transmitter RF-output option. ULX-D provides sophisticated network capability so the receiver can be monitored across subnet by third-party devices. ULX-D also offers dual and quad receivers with such features as Dante digital audio networking, integrated Ethernet switch, frequency diversity, audio summing, and simplified hardware setup.

The TRX series of digital wireless microphones feature patented internal backup recording with timecode and RF remote-control reception. Other features include 100%-digital modulation, digital dropout protection, five- to nine-hour running time (depending on model), a graphic LCD display, and no intermodulation; up to 50 transmitters in the same frequency block can be used simultaneously. Timecode transmission and reception can also be distributed through ZaxNet, Zaxcom’s 2.4-GHz signal network, to other transmitters and receivers, keeping the entire workflow in perfect timecode sync.

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