For AV professionals in the broadcast industry, the qualitative advantages of digital wireless audio technology are clear. But in some situations, the drawbacks — like lower power, bandwidth, and interference resistance — are just as pronounced. When Jon Alpert is shooting a documentary about the Iraq war from a military hospital on location, the Downtown Community TV co-founder knows DCTV’s technology choices are as critical as its missions.

Advantages of a hybrid system

    16 Emmy awards suggest DCTV makes good choices. In 2006, Baghdad ER won a Primetime Emmy Award for Outstanding Sound Editing for Nonfiction Programming. DCTV employs four Lectrosonics UM450 beltpack transmitters and UCR411a compact receivers to capture the sound quality that has become a DCTV trademark. Lectrosonics systems have the advantage of Digital Hybrid Wireless Technology (DHWT), which harnesses the advantages of both digital and analog systems to capture digital-quality audio, and cut out the setbacks of digital transmission.    

Wireless audio system users with interference and bandwidth concerns once settled for conventional analog systems, which come with built-in compandor technology - and unwanted sonic artifacts - for the sake of increased dynamic range. Without sacrificing dynamic range performance, DHWT has ousted compandor technology, and the artifacts that come with it.

Using the company’s algorithm, a DHWT transmitter, like the UM450, digitally encodes 24-bit audio information, sans compression and with minimal distortion, and reformats audio data to send over an analog FM link. Lectrosonics’ frequency synthesized UHF receivers like the UCR411a use smart filters; RF amplifiers; mixers; and a sensitive detector to capture the encoded signal. A Digital Signal Processor decodes the audio data from the analog FM link, so the system retains digital quality audio with analog quality ease. Users retain the long-lasting power; sophisticated interference resistance; long operating range; and the efficient, simultaneous channel operation capabilities of a small spectral FM wireless system.  

Guaranteed performance

    In the war zones where DCTV has operated — including Afghanistan and Iraq — the necessity of using wireless audio equipment is a no-brainer. Choosing the most suitable wireless system requires some thought. Says Alpert, “The gear I use needs to be intuitive and, at the same time, meet very high production standards... Many of our documentaries are created in some of the most hostile environments on Earth.”

Production professionals perform under treacherous conditions, and it is essential that their AV equipment does, too. Ultra-stable RF performance is non-negotiable.  In a violent atmosphere, AV equipment mobility is almost as important as its operators’. Where there is noise turbulence, the signal to noise ratio is as important as the content it has captured. A product’s build quality has to be as sturdy as its operator; AV equipment has to handle everything that professional AV users do. According to Alpert, Lectrosonics systems are designed to meet the challenge.
  
DCTV’s technical considerations included competing radio frequencies, the presence of diverse electronics in medical evacuation helicopters,  and, of course, the sound of the chopper. “Even in this type of setting ... we have got remarkably clear audio quality,” Alpert explains. “You can’t ask for more than that.” Considering the hurdles, the quality of DCTV’s audio footage is simply amazing, Alpert says. And for tech professionals, the concept behind the DHWT is amazingly simple. The DSP minimizes DCTV’s risk of multi-path interference on the compact receiver with SMART Diversity technology. By engaging the phase diversity network and PIN diode RD switch antennas simultaneously, the microprocessor supports effective diversity reception as it recovers the original, digital audio data from the analog wireless link.

Alpert’s UM450 transmitter and UCR411a are going strong after four years, but the self-titled “fanatics” at Lectrosonics are onto the next step.

Lectrosonics discontinued the UM450 transmitter and developed the new, functionally identical UM400a. The UM400a has lower RF output than its predecessor (100 mW versus 250 mW), and, with the same deviation of +/- 75 kHz wide as the UM450.
 
Virginia Rubey is a New Orleans-based writer.