Tech Focus: Bodypacks, Part 1

Small, lightweight transmitters adapt for spectrum changes and move into new sports

In the world of bodypack transmitters, size still matters. The value of athlete audio and on-field sound continues to increase, putting a premium on devices small and light enough to not interfere with play but able to reliably reach a receiving antenna and to do so cost-effectively. Smaller, lighter, cheaper is the mantra.

But there are still plenty of other issues facing manufacturers. Most notable is the looming loss of RF spectrum as the FCC-controlled bandwidth auctions, scheduled for mid to late 2016, creep closer. Once the auctions have been completed and a 39-month infrastructure rebuilding period is through, bodypack manufacturers and users will be looking at significantly truncated usable spectrum, with much of the prized 600 MHz band — if not all of it — no longer routinely available.

Karl Winkler, VP of sales, Lectrosonics, whose bodypacks are used by the NFL and NHL, points to the company’s newest bodypack product, the Super Slim Mini, which has two-thirds the weight of its lightest existing unit, as a reaction to the physical demands on bodypacks now. But spectrum loss, he adds, was behind development of a new IFB system, which uses the VHF (174 MHz-216 MHz) part of the spectrum to free up UHF bandwidth for audio to be used on the air.

“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,” he explains. “Spectrum loss is making us make better use of what will be left.”

Encryption has also taken on new levels of importance. As on-field communications have increased, so has what seems to be opposing teams’ desire to listen in. Allegations of eavesdropping against the New England Patriots and the New Orleans Saints in the last dozen years have underscored the pursuit of ever higher levels of protection for wireless communications.

Encryption strength is constantly improving, Winkler says, with 256-bit AES encryption now the gold standard for the industry. “Key length and key management are the main points when it comes to encryption,” he says, referring to the encryption algorithm established by the U.S. National Institute of Standards and Technology (NIST) in 2001.

Such features as enhanced spectral efficiency and higher-resolution digital audio will also be migrating onto the playing field, opines Stephen Kohler, senior director of marketing, Shure, whose wireless microphone systems are widely used by on-air talent at sports events. “It’s all about improving the consumer experience, and that leads back to the bodypack or the transmitter in the helmet.”

More Sports
Despite the challenges of spectrum constriction, compact bodypacks will only grow in demand as new sports add athlete audio to their broadcasts. Quantum5X, whose PlayerMics have been on NBA players for years, has been working with rugby teams in the UK and Australia, as well as with at least one MLS team in the U.S., the Philadelphia Union, according to CEO Paul Johnson. Rugby, he notes, is using a variant of the PlayerMic worn between the player’s shoulder blades and kept in place with a compression vest. NBA players wear them in pockets on the side of their jerseys.

“The thing with sports that don’t use padding is that the transmitter has to be very small but also has to be designed to avoid injuring the player if he falls on it or is tackled near it,” Johnson explains. “Player safety is the big issue.”

He notes that the bodypack’s strain-release connectors and flexible housing are designed to achieve that goal but stresses that the flexible-housing design is intended to keep the device transmitting.

The housings for bodypacks used by rugby and soccer are slightly larger than those for basketball, to accommodate a larger battery with longer running time. The MLS versions are also the first to use transmitters that operate in the 500 MHz range, the leading edge of Quantum5X’s long-range strategy to move its entire product line into that frequency range, in anticipation of the loss of the 600 MHz band. These bodypacks house an antenna whose length has increased by about 1 in., needed to accommodate the lower frequency range.

“We’re relaunching the entire product line around that now,” Johnson says.

A Local Issue, for Now
Accommodating reallocated RF spectrum will be a U.S. problem for the foreseeable future, according to Joe Ciaudelli, director of spectrum affairs, Sennheiser. He was recently a member of the U.S. Department of State’s delegation to the World Radio Conference in Geneva. There, European and national broadcast agencies rejected the U.S. initiative to reallocate UHF spectrum to mobile devices. The quadrennial conclave won’t take the matter up again until 2023, he says, and, even if it did, implementation would keep the 600 MHz band there safe at least until 2027.

In the upcoming, reallocated U.S. RF landscape, Ciaudelli says, wireless users will be working in the 500 MHz range, along with some of the carved-out remainders of 600 MHz, in that range’s guard bands and duplex gap. However, he adds, wireless will also be moving upwards, into the 900 MHZ and 1.4 GHz ranges, which the FCC has cleared for professional use. There, he says, users will have to learn a few new tricks.

“As you go up in frequency, not only does propagation diminish, but body absorption of radio waves really increases,” he explains, further reducing RF reach. Best practices to counter that include ensuring that no part of the antenna comes into contact with the body or with sweat-dampened clothing — not an easy task in sports.

Bodypacks’ importance in broadcast-sports audio will increase at the same time that the technical challenges are also growing. Break out the popcorn: this will be an interesting narrative to follow.

Click here for Tech Focus: Bodypacks, Part 2.