Technology Showcase: Wireless Mics
Jun 1, 2005 12:00 PM, By Gary Eskow
UHF systems provide users with more available frequency for less interference.
It's easy to understand why wireless microphones are so popular. Why would you want to be tethered by wires when you could fly free, showing off your flow charts in all directions or belting out a song-and-dance number without wondering if you'll accidentally choke yourself?
VHF VS. UHF
Although VHF wireless microphone systems are still offered, the popularity of UHF systems has grown appreciably. What are the differences between the two protocols?
Tim Vear, a senior applications engineer at Shure, categorizes the differences between the VHF and UHF spectra as regulatory differences established by the FCC and physical differences having to do with the wavelengths of the signals.
According to Vear, “The wavelength of a typical UHF signal is about 15in. to 20in. VHF wavelengths are about 5ft. The difference directly determines how the signals behave as they are transmitted through the ether or through wire or cable. Antenna size also comes into play: VHF signals require longer antennas than UHF signals. On the other hand … longer wavelengths penetrate [non-metallic] objects better than shorter ones.”
Tom Stotler, product manager for wireless microphones at AKG, emphasizes the importance of taking into consideration changes in wireless technology. “When UHF came to fruition, most of the VHF spectrum was [and still is] very populated from local TV stations. Because wireless at this time was not frequency-selectable, many wireless users who traveled, such as touring companies and musicians, requested and eventually moved to UHF because it was less inhabited.
“As UHF television stations became more popular in this country, the need for selectable-[frequency] systems, both UHF and VHF, became obvious. While VHF is still viable in many applications, most manufacturers are now no longer investing in this technology. It's all about avoiding interference. The UHF spectrum is now becoming very crowded, and the technology we see today, with frequency scanning systems, is addressing this issue. As the RF environment continues to change along with the demands of the users, so will the manufacturers.”
Audio-Technica's Steve Savanyu believes the days of the wide-open frontier may be drawing to a close. “The VHF area of the spectrum became crowded very quickly, but there was lots of space up in the 60s, and manufacturers of UHF systems took advantage of it. A lot of money was poured into the development of UHF wireless microphone systems. But the FCC is looking to auction off parts of the spectrum. The high 60s are just about gone.
“The growth of digital television is another factor that must be considered. Back when analog TV was the only game in town, you could sneak wireless channels around the analog signals and not affect anything. There can be problems if you stay close to the DTV signal these days, and so we're expanding our bands up into the 500[MHz] and even 600MHz range.”
Still, VHF does have its selling points. “If you're running coaxial cable for a remote antenna location, the losses are much greater in the UHF range,” says Vear. “You have to use low-loss cable, antenna amplifiers, or both, if you plan on using UHF under these conditions.
He adds that UHF systems are subject to more multipath dropouts than VHF. “With wireless microphones, the problems caused by delayed signals [reflected by metallic objects] can be severe enough to render the signal unusable.”
Wait, it sounds like VHF is preferable, right? “No, for one overriding reason: available bandwidth,” Vear explains. “The VHF spectrum covers about 40MHz of bandwidth [from 174MHz to 216MHz, specifically], while the UHF range goes from 470MHz to 806MHz. That's almost 10 times more available frequency, which translates into many more channels. In the VHF range, you're limited to running about 10 to 12 channels at one time. The UHF bandwidth can potentially accommodate up to 100 channels running simultaneously, if there is coordination among the various users.
“Finally, many applications require traveling from city to city, and in those cases, the operator must be able to retune the wireless system to avoid interference from local television channels … if you're staying in one place and you don't think the longer wavelengths will cause phase problems, VHF systems are perfectly fine. In all other cases, the user has to give serious thought to a UHF wireless microphone system.”
We'll scan the wireless field and show you a sampling of what's available.
Shure manufactures a wide range of wireless UHF products — from entry-level systems to top-of-the-line. Recently introduced is the PGX series. Tunable over an 18MHz range, the PGX series makes frequency-agile UHF systems available on a budget. With a list price of less than $700 for a complete system, the series offers eight packages with microphone/transmitter options including handheld, lavalier, head-worn, and instrument.
Shure is currently developing a high-end UHF system that will tune over a 60MHz-plus range. Expected to be released by the end of 2005, this system will have computer networking capability and integrate up to 100 channels in a single location.
AKG's WMS 4000 system operates in four 30MHz UHF bands, with 1,200 frequencies in each band, permitting simultaneous operation of at least 50 systems. The PT 4000 bodypack transmitter features a backlit display for setup and status monitoring that indicates remaining battery life in hours, frequency, channel or preset groups, gain setting, and mute status. The HT 4000 handheld transmitter is available with six different microphone options. Integrated charging contacts allow charging of the optional BP 4000 battery pack, which requires one hour of charge time for 12 hours of continuous use.
Accessories include the PS 4000 multi-coupler for antenna signal and power for four SR 4000 receivers. Additional outputs allow signal cascading to other PS 4000s. The PSU 4000 central power supply powers up to 12 SR 4000 receivers, as well as the CU 4000, HPA 4000, and HUB 4000. The HUB 4000 PC network integrator an MCS 4000 software allow connection of up to eight SR 4000 receivers to an Ethernet network. The system can be expanded using standard PC components such as Ethernet hubs or wireless LAN interfaces. The software allows remote control and monitoring of a complete multichannel system on a single screen. The program includes a graphic spectrum analyzer and frequency management database.
Sennheiser offers systems for a wide range of applications — from vocal performance, to lecture and presentation, to theater systems. Sennheiser's Evolution wireless G2 systems offer three separate 36MHz tuning bandwidths covering 1,440 selectable channels each. The Autoscan feature allows users to find an open, intermodulation-free frequency for use with multiple G2 systems. G2 offers rackmountable, dual (EM550G2), and portable receiver options, coupled with multiple transmitter options featuring Sennheiser lavalier and microphone capsules. Sennheiser's 3000 series and 5000 series can be tuned anywhere in the UHF bandwidth (450MHz to 820MHz). Sennheiser has also teamed with Neumann to create the SKM5000-N performance handheld wireless microphones.
The compact Lectrosonics SM transmitter measures only 2.3"×1.8"".64". It features a 100mW RF output and is programmable via front-panel membrane switches. Digital Hybrid Wireless technology provides compandor-free audio in native 400 mode and several analog transmitter compandor-emulation modes. A newly designed input circuit allows for connection to an array of microphone types via the SM's standard TA5M connector.
The MM400B is an update to the Lectrosonics water-resistant Digital Hybrid Wireless transmitter line, with a programmable, completely waterproof switch for muting or power. The MM400B provides 100mW of RF output and is frequency-agile, with 256 frequencies available in each of the nine standard Lectrosonics frequency blocks.
Nady Systems' U-1000 series features a choice of 1RU single (U-1000) or dual (U-2000) receiver configurations, both with true-diversity operation; maximum frequency agility, with 1,000 channels per 25MHz group within the 600MHz to 900MHz range; AutoSearch scanning for available clear channels; and dual-band companding. LCD displays with step-through menus are available on all receivers and transmitters. An AutoTransfer function allows automatic download of setup information data from the receivers to the transmitters via a supplied USB cord. Digital Tone Squelch eliminates spurious interference from other RF sources, and two AA batteries provide convenient, economical operation for extended transmitter life. Single-use alkaline batteries or repeated-use NiMH batteries can be recharged internally via an external USB cord from the receiver. The handheld transmitter also provides QuickChange snap-in capsule module replacement.
Sabine's Smart Spectrum SWM7000 wireless microphone system allows the use of up to 70 channels simultaneously in the 2.4GHz frequency range. Features include built-in DSP processing, and FBX feedback exterminator and parametric filters. Each receiver provides 10 filters per channel, individually selectable as either parametric or FBX filters. The system also provides a library of “virtual” capsules that model the sounds of popular microphones. Compressor/limiter, adaptive de-esser, handheld, and beltpack transmitters feature LCDs that indicate battery strength and hours of use, information the system also transmits to the receiver. SWM features full front-panel control and SWM remote software allows control of up to 70 channels. The Sabine Audio Control Snake provides serial control down a mic snake line, allowing FOH control of stage-mounted receivers.
The TOA Electronics WT-4820 accepts one or two WTU-4800 diversity modules, with simultaneous operation of up to 16 user-selectable channels in the UHF band (692MHz to 722MHz).
Features include individual channel outputs, mix output, and antenna cascade for sharing antennas between two units. A mix-in jack allows connection to the audio output of a second WT-4820 or other source. Handheld transmitters include the WM-4210 dynamic for vocals and the WM-4220 condenser for speech. Bodypack transmitters are available, including the WM-4310 lapel, WM-4310A aerobics/fitness headset, and the WM-4310H speech headset. All transmitters offer 10 hours of operation from one 9V battery, with low-battery indication.
Anchor Audio's UHF 6400 systems — the WH-6400 handheld transmitter or the WB-6400 bodypack transmitter — feature 64 user-selectable channels and a headphone output with separate volume control. The transmitters can be recharged from the base unit. A rackmount kit is included for installation of one or two units. The bodypack transmitter features a mic/line switch to wireless transmission of line-level devices (CD player, etc.).
The Pro Comm PCX U1002, a 100-channel UHF system from Peavey Electronics, employs AutoScan technology to automatically search for non-interfering channels. The transmitter also features CCS (Channel Control System), which sets the channel on the transmitter. An LCD displays channel and battery status and group information. The ½RU PCX U1002 receiver includes XLR and ¼in. outputs. Pro Comm PCX U1002 systems are available for less than $900. Peavey also manufactures the PCX U12 and PCX U302 systems.
The Gemini UZ-9128 true-diversity system ($489 MSRP) offers 128 selectable UHF synthesizer-controlled frequencies, LCD displays on the transmitters and receiver, and a 400ft. range. It also provides RF and AF LED meters and a ½in. headphone output for independent monitoring of each system. The system is available in handheld dynamic, as well as lavalier and headset condenser configurations, and comes with rackmounting hardware. Also included is an antenna breakout kit that allows the antennas to be remotely mounted when the unit is installed in a rack.
Sony's UWP-C3 wireless microphone package includes a plug-on microphone transmitter, a portable tuner, and component accessories. The UWP-C3's plug-on transmitter effortlessly converts a wired microphone into a wireless.
The microphone package achieves stable transmission and reception by incorporating a UHF PLL (phase locked loop) frequency-synthesized system and dual antenna inputs/reception circuits that automatically select the strongest available RF signal for output. Up to 16 wireless microphones may be used at one time. A portable tuner features angle-adjustable antennas designed to eliminate signal dropout.
The turnkey wireless microphone system will be available in September 2005 at a suggested list price of $699.95.
Audio-Technica's 5000 and 4000 wireless systems feature IntelliScan, which electrically links multiple receivers. When the IntelliScan feature is activated, the total number of receivers in the system is counted. The first becomes the master, and a coordinated frequency plan for all linked receivers is built.
The Artist Elite 5000 system features dual independent receivers and includes a pair of transmitters in a single 1RU, rackmountable chassis. The transmitters share antennas and a built-in network card. The Artist Elite 4000 series is a single-channel, ½RU system that features one transmitter and one receiver. It can be configured with a beltpack (for lavalier, head-worn, or instrument input options) or a handheld microphone (four mic capsule options).
In 1962, Beyerdynamic launched the Transistophone, which the manufacturer claims was the first wireless microphone in production. Currently, Beyerdynamic's Opus series offers three levels of wireless UHF systems. Opus 300 includes a handheld or bodypack transmitter and a receiver. The Opus 300 offers frequency scanning with 16 tunable frequencies. The system can run up to 10 receivers simultaneously. The Opus 500 Mk II wireless system features 100 pre-programmed frequencies. A color LCD display indicates frequency, group and channel, squelch, battery status, user's name, and RF and AF levels. The Opus 800 uses a 1U-high main frame with four slots for connection to four modular NE 800 receivers (which have the same electronics as the Opus 500). The Opus 800 software can be adjusted, monitored, and controlled via PC for use with a multichannel system on tour or in permanent installations. The software features realtime control of up to 64 channels or NE 800 receiver modules; manual frequency selection or selection via integrated spectrum analyzer; setup and monitoring of AF/RF level, diversity status, battery status, channel, frequency, etc.; and a memory function for system settings.
The 7100DX Quad-Rak dual-diversity UHF wireless microphone system from Lightspeed Technologies features four independent UHF 100-channel, frequency-agile wireless receivers in 1RU. The Clear Channel Scan feature automatically selects the best channel to use. The mic can be configured with up to four receivers, mixed balanced/unbalanced outputs, five macro frequency groups, a low-battery indicator at the receiver, individual balanced outputs, TS Tone Squelch, integrated antenna distribution network, and 3/4 wave antennas. Microphone options include lapel, handheld, headset, and earset.
EV offers the RE 1 and RE 2 wireless microphone systems. The RE 2, its latest product, offers Auto-ClearScan to locate the clearest channel/group and a unique “guitar” setting optimized for a wireless guitar system. Frequency selection is programmable in 25kHz steps across 28MHz bandwidth for a possible 1,112 frequencies. Complete packages are available with handheld and bodypack microphone options.
Clockaudio's CW9000 features 192 PLL-selectable channels per UHF band. The true-diversity system includes tuned antennas and two independent receivers for optimal reception in poor conditions. Receivers are made of rugged metal and come in a compact ¼RU size with easy controls, LCD display including battery status, and balanced XLR and unbalanced ½in. jack outputs. Internal squelch and mute are provided to minimize noise. The CW9000 is available in handheld, beltpack, or combination versions to accommodate different applications. The handheld version can come with a dynamic or condenser capsule, while the beltpack can include either a cardioid or omni lavalier microphone. Antenna extension, splitters, and boosters are also available when multiple systems are required.
Telex produces the SAFE-1000 encrypted UHF system for environments that require secure wireless communications, including courtrooms, boardrooms, and conference centers. The system features digitally encrypted transmission of more than 950 possible channels. Up to 16 systems can operate simultaneously from preset channels. Other features include advanced ClearScan, automatic group and channel selections, a backlit LCD display that shows the group/channel, diversity operation, RF and audio level meters, and space for a custom label. Telex also manufactures the FMR-500 and FMR-1000 systems.
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