… one roadie’s opinion on the important stuff in wireless technology
It was all there, summed up on the back of the blister pack.
“Rock on, and feel the power of wireless freedom !”
That’s what it is. It is freedom to wander about, impinged only by my ability to successfully walk and chew gum at the same time. It is freedom to spin in an eternal clockwise motion whilst emoting. In this case it is the freedom to click on the boom-box and play my fave Gibson sans cables wherever I am.
It is a good example of what wireless doo-dads are to a musician – taking off the leash. My first wireless was an old low-band system, something like 49hz. It sounded like crap. I couldn’t get more than fifty feet from the receiver. It picked up a religious AM station or the airport control tower, depending on the day of the week. But it was a wireless.
This one is NADY’s FM transmitter for guitars, the AX-1000. I’ve forgotten what it cost, but it was too cool to haggle over price. It does exactly what it should, and it has echo too. It was just right for my coffee-break/jam-sessions.
I see wirelesses in live performances of all types these days, from football stadiums, to Broadway, to Mom’s garage. Some of the new units cost way more than my car… then again so does a nice bicycle, which is sort of the point. The demands of audio fidelity vary tremendously from use to use, and when you get picky about fidelity you’re going to need deep pockets.
Wireless microphones, for example, can be nearly transparent. The expensive systems are almost better than a hardwire. Cheap units could make Pavoratti sound like an asthmatic at a smoker’s convention. The reasons behind this disparity are classified. All of us who seek to learn the mystic ways of the radio wave are sworn to secrecy. Only those who will maintain the vow should read further.
A wireless system is designed around a few circuits, the transmitter/receiver(TX/RX) itself, the compander section, and the diversity section. TX/RX circuits are fairly simple unto themselves, and essentially they are all the same. One important tech spec to look for is signal-to-noise-ratio or s-to-n. This describes the electrical difference between the loudest signal a transmitter can send without distortion, and the point where wireless/electrical noise is audible, measured in dB (larger s-to-n ratio is better).
Pay particular attention to the physical construction of the system, especially the beltpack/handheld transmitters. The component used for a system’s tuning, usually a quartz crystal oscillator, is secured in the TX/RX circuits, but the road is hard on people and machines. If your budget allows, stick with rack-mounted receivers, and learn to care for extremely delicate equipment. I send every wireless I expect to use back to the manufacturer to be tuned at least once a year, whether it seems to work okay or not. You can use a scanner or a frequency counter to check transmitters, but receivers need professional mojo.
Most wirelesses are built with a compander circuit hidden away from our prying little fingers. Com- for compressor, and -pander, as in expander. The idea is to compress the input so as not to distort the transmitter, then to expand the signal to its original, pristine, fresh-from-the-artist state at the receiver. Success in this area is often limited. For some applications it isn’t so important, but on a vocal microphone excessive action from the compander can be quite annoying. Some transmitters will have an input trim on the transmitter (to allow for a whispering singer or a screamer who sings), and that’s a good thing, but make sure it is recessed in the unit. It should only be adjusted once – after that you can generally forget it until you move the transmitter to a different use.
Most manufacturers today sell diversity systems. Diversity isn’t really accurate, “this-or-that” is a more apt description of how they perform. (If it were truly diverse, it would be a wireless system and an espresso maker….) A diversity system uses more than one receiver on the same frequency, usually exactly one more, and simply uses the best signal. There are a few ways to build diversity systems, depending on the particulars of how it selects the receiver it will use, and on how it switches between them. I never noticed much difference between the styles, and personally I’d advise not to sweat it. You’re better off trying to maximize signal strength.
Which brings us to the next major part of your system – its antennae. Antenna technique is overlooked more often than any other part of the wireless set-up. A little attention to detail goes a long way when using wireless systems, especially in heavy-radio-traffic areas. Signal quality depends on the amount of background radio noise in your environment and on the efficiency of your antennae. Background noise is a tough one. Some systems will let you choose the quietest of two or more frequencies (I have 160 frequencies on one system) and that’s the best solution, i.e. find the clearest frequency available to you.
There are many different types of aerials, and most systems allow you to remove the antenna and replace it if you wish. Antennae are based on wavelength, which is a function of frequency, so antennae are ‘tuned’ to the general bandwidth of the system. Most of the time, changing the aerials isn’t nearly as helpful as we’d like, but every little bit helps. Shure Bros. sells a series of half-wave antennae for the VHF bands which are cost effective, for example. For UHF systems, the little rubber antennae that come with the system are usually enough.
Therefore two parallel antennae will (or won’t) “see” the same wave at approximately the same strength, especially if they are less than one wavelength apart. This is often noticeable with VHF rack mount rigs where the aerials are 18 inches or so each other. [Double-secret bonus antenna tweak: point both antenna straight up, then pull one antenna toward yourself 45 degrees, then turn it clockwise (or counter-clockwise) 45 degrees. In this position the antennae share no planes, therefore maximizing the possibility of one antenna being able to dredge up a usable signal.]
Antennae can be changed and moved, but there are two big rules to follow. (1) Always try to maintain line of sight to the transmitter. Steel beams, scaffolding, air conditioner ducts, poles, people, Polish people… anything between antennae and transmitter can cause trouble. Radio waves may also “phase” due to reflection, like sound waves, but a good line of sight policy will usually allow the direct signal to be received clearly. (2) The less cable and the fewer connections between receiver and antenna, the stronger your signal will be. Adapters, 1-meter extension cables, and those pretty rack-mount panel jacks cost signal strength. A few of these little problems in the same room can cause unpredictable behavior, including distortion, drop-outs, and smashed transmitters.
The most important part of a wireless system usually comes in the box from the manufacturer, but it always wears out. Every-freaking-day, sometimes twice-a-day, these things have to be replaced. That’s right. I mean the battery. Wirelesses pretty much suck without them. Do yourself a favor by buying the good ones. Cheap batteries are cheap because they don’t measure up. There is no sense in screwing up any gig that pays for want of a two dollar battery.
Now I’m sure some of you are wondering about wireless personal monitors. Should you get them? Are they cool? Who makes the best? No, yes, and I can’t tell you. What’s best is different for everyone. The facts are hard-wired personal monitors can sound great, and even the best wireless systems sound pretty darn good at best. Wireless should only be considered by those who absolutely must run amuck, or by those with enough money to buy one of everything. That notwithstanding, body-worn receivers need to be insulated from the artist’s skin, receiver antenna go outside the costume, and you should at least use ground-plane antennae for transmitting. Wireless PM’s require a careful touch to squeeze a good mix into a limited s-to-n range. Compression at the monitor desk is your friend. Try to drink lots of water. Besides that, treat like all other wirelesses.
If you decide to buy a new wireless system, decide what your budget is before you start shopping, do some research, then shop around. Good, functional, inexpensive wirelesses can be found. Being informed can only do you good. You can build a FM transmitter kit from a hobby store for ten bucks and use it with a boom-box. The top of the line systems start around five-grand.
Freedom has its price and, hey, it’s your money.