Wireless Mics, part 1 of 2
Should you go wireless?
A huge chunk of my daily professional life if spent understanding, and maximizing the performance of, wireless entertainment equipment (mics, two-way radios, theatre communications, and in-ear monitors), and still, my first choice is always to use a hard-wired (non-RF) alternate. I’m not sayin’ wireless is evil, but I am saying it’s less reliable than its hard-wired brother. There are, however, obvious arguments for using wireless mics: Mobility is the most common. If you’re wandering around a stage, producing doves or executing elaborately choreographed musical transitions, you can’t be draggin’ a mic cable around with you!
Here in Part 1 of this guide, we’ll look at some differences between the three main wireless frequency options: UHF, 2.4GHz, and VHF. In Part 2, we’ll look at how to make any wireless system perform its best.
First, though, let’s debunk some ‘urban myths” around wireless mic systems.
- Urban Legend # 1 – “What wireless system does Copperfield use? His never drops out!”
The possibility of RF dropouts is a pure & simple fact of life. Even the most expensive RF system, operated by world-class RF techs, is susceptible to dropouts and other interference. The good news is that this guide will help you to minimize them.
- Urban Legend # 2 – “What wireless system does Copperfield use? His sounds GREAT and never feeds back!”
Assuming we’re comparing systems of professional quality, anywhere from “entry level” pro to “Broadway” pro, the wireless system has almost nothing to do with sound quality or feedback. Basically, sound quality & feedback are functions of microphone selection and PA operation. The quality of the wireless system affects dop-outs, interference, and other non-sound-quality-related issues.
- Urban Legend # 3 – “The big theatre pros just tuck their beltpacks into special pockets.”
While this is true, keep in mind that the beltpack’s antenna must be allowed to extend to its proper length for maximum efficiency, and must not be touching anything conductive, including skin. Sweaty skin is even worse.
- Urban Legend # 4 – “As long as two RF systems aren’t on the same frequency, they won’t interfere with each other.”
Not true. The math behind finding simultaneously compatible RF systems is pretty involved. Even if no one else is using a wireless system, you might encounter problems. If you plan on buying or renting more than one system, make sure that the vendor has ensured compatibility between them. The manufacturer is an even better source of info on this. Remember, as well, that the interference you encounter will change from city to city and from venue to venue, and can even affect a portion of your performance area as small as 7.5cm x 7.5cm (3” x 3”)!
In the US & Canada, all of the RF systems that the law allows us to use is in the same frequency range as VHF & UHF TV, so especially if you work in a major centre, be sure to check with the manufacturer about “broadcast TV compatibility”.
Digital audio signal processors, digital recording and playback devices, hard drive recorders, digital electronic musical instruments, MIDI-controlled instruments, and stage lighting controllers can all cause buzzing in your RF system, so do your best to avoid having your transmitter or receiver within a few feet of them. Close proximity to stage lighting dimmers and neon or fluorescent lights can also be a big problem.
- Urban Legend # 5 – “The store said my RF would work up to 300 feet!”
Due to the countless variables one might encounter (obstructions, reflections, RF interference), it is impossible to predict the useable distance of an RF system, so don’t believe what the store or even the manufacturer tells you. Besides, a cardinal rule in the use of RF is to maintain the shortest possible unimpeded line-of-sight between the transmitter’s antenna and the receiver’s antennae. Don’t make distance an issue!
- Urban Legend # 6 – “You can save a bundle by using rechargeable batteries in your RF transmitter!”
Use the batteries that are recommended by the system’s manufacturer. These will usually be alkaline batteries because alkalines are more reliable, have a much greater useable life and a greater shelf life than other types. If a manufacturer sells a rechargeable system specifically for their wireless mics, consider it, but they simply do not last as long PER USE as alkalines.
Turn the transmitter off between performances to extend battery life, but do not turn it off during the performance, because you’ll occasionally forget to turn it back on.
- Urban Legend # 7 – “It’s best to keep the receiver at FOH!”
One of the most unknown and/or deliberately unobserved rules of RF usage is that sound people choose to put the receiver at FOH (the “front-of-house” mixer position) so that they can see the RF level (RF signal strength) meters. Unfortunately, this also means that since the RF is having to travel a greater distance, and since there are more human obstructions along the way, the signal strength will be compromised! So, basically, the choice is as follows:
- Keep the receivers at the stage where you’re not able to see them, and know that they’re performing better, or,
- Keep the receivers at FOH where you are able to see them, and know that they’re performing worse
Comparing UHF, 2.4GHz & VHF
UHF is what everyone’s been using for the past 15 years. The problem is that governments have been selling big chunks of the UHF frequency range, making those ranges illegal for use in wireless mics, wireless in-ear monitors, wireless two-way theatrical communication, etc. Both Canada and the US did big auctions of these UHF frequencies in 2010 & 2016, making a great many entertainment wireless systems illegal, and very susceptible to interference.
VHF wireless mics pretty-well stopped existing a bunch of years ago, due to the advantages of UHF. Well, with governments taking away more & more usable UHF bandwidth, VHF is finding its way back into the market with improved features. This also is why 2.4 GHz systems have emerged.
About 2,4-2,5 GHz
Line of Sight
Of the three, UHF is mid-capable in terms of its ability to go around physical obstacles.
Of the three, 2.4 GHz is least capable of going around obstacles. In other words, it is very important to have an unimpeded line-of-of-sight between the transmitter’s antenna and the receiver’s antennae.
Of the three, VHF is most capable of going around physical obstacles.
Considering good quality systems, all three bands easily should be able to operate up to 45m/150′. Ignore any claim that a vendor or manufacturer might make. Remember, you’ll get better performance by keeping the receiver at the stage rather than at a mixing position out on the audience.
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Modern & credible UHF & VHF wireless mic systems in all three bands have the on-board ability to choose from a number of operating frequencies. So, if you are experiencing interference on one frequency, you can try other frequencies.
2.4 GHz wireless mic systems have the ability to find interference and avoid it.
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Given systems of similar quality, all three bands will provide very similar sound quality. In other words, mic selection and usage will make much more difference than which frequency band your wireless components use.
As noted I’m talking about SYSTEMS OF SIMILAR QUALITY. A $200 wireless system found on AliExpress, DHGate, etc is not of similar quality to a wireless system from Shure, Sennheiser, Audio-Technica, AKG, Sony, or Line6.
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Maximum Number of Systems at a Time
Modern UHF & VHF systems both can have many systems operating at one time. Coordinating these systems to operate together in the ever-shrinking spectrum gets more difficult as you add more wireless, and is more difficult in urban areas where there are lots of TV channels.
Usually, you can use no more than eight 2.4 GHz systems at a time, and that is under ideal conditions with little-to-no WiFi router activity in close proximity, and in urban areas, WiFi is pretty-well everywhere.
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Well, that’s the end of Part 1, concerning some urban myths and basic comparisons of UHF, VHF & 2.4 GHz wireless mics. Tune in next time for “Wireless Mics, part 2 of 2“, with proven advice on how to make ANY wireless system to its full potential.