We’re going to keep the tech level low here because we’d rather take the time to explain how to use them and make you familiar enough that you are comfortable with them. However, we highly recommend that you do some background research on your own. Radio and transmission technology is truly fascinating stuff and is the backbone of virtually any gadget you pick up today
First and most obvious, you have your pickup, or microphone. They come in all sizes and types, just like regular mics. Indeed, in many circumstances you could take an adapter and plug a standard microphone into a wireless system and it would work just fine. You might find they have different jacks than those you are used to seeing, or come with a fancy head bracelet, but the technology is the same as any other standard pickup.
Normally, at this point you’d plug in a cable and run it from the mic to the mixer or camera. In this case, we’ll remove the cable and put a transmitter at one end and a receiver at the other. There are essentially two types of transmission/reception technologies that we’ll want to look at.
The first, and probably least likely you’re going to come across or have a need for is the infrared system. Just like your television remote, you point the transmitter at the receiver and it sends invisible, encoded light waves from the source to the destination. These systems require a direct and uninterrupted path from one end to the other. As such they are very secure and incur almost no interference. They are very limited in function however as they are all but useless outdoors (that big fiery ball in the sky gives off Infrared light too) and you can’t move them around. Still, in a stable and controlled environment where you need to get a quality signal from one end of the room to the other without wires, they can be ideal.
The second system is radio transmission. The same types of signals used by your radio, television and cell phone are used to send audio from your talent to your recorder. Within this, there are three sub-groups.
The first group is the VHF (very high frequency) group. Remember in the old days television stations used to broadcast channels two through 13 on the VHF spectrum. All this means is that the powers that be got together and set aside a certain range of signals to broadcast on. Indeed, if you’ve ever looked at an old television and wondered why there was no channel one, it’s because they set aside that range for broadcast radio and communications systems like walkie talkies and wireless microphones. Like channels two through 13 on your old television, the VHF range is the most popular for wireless mics and is generally the cheapest to gain access to.
The second group sends signals on frequencies similar to that other set of old tv stations, the UHF (Ultra high frequency) range. This is a more exclusive range to work with and handles certain types of interference better than VHF. Traditionally wireless systems operating in this range are considered more for the professional recording industry and are thus more expensive, though the prices have narrowed greatly.
The third is a digital transmission system. Think of this as your modern television system. Instead of sending analog audio, it communicates only with zeros and ones.
Now logic might imply that you should always jump for the latest and greatest technology and go straight for digital, right? The truth is that all of these systems have instances where they are optimal and uses where something else could do a better job. Which one you should choose will naturally depend on your operational circumstances.
Again, avoiding the technical details, VHF is great if you are on a budget, only have a need for two or three microphones operating simultaneously and are in a location where interference is low. A crowded city may not be the best situation here. VHF does have a good range however and tends to penetrate through solid objects better than others. UHF will be best suited for shorter range transmissions and situations where you have more than a couple systems working at the same time. UHF requires more power and is not as good at penetrating walls. It wins out over VHF when it comes to cutting through static and interference, especially when there is a line of sight to the receiver. Digital systems and digital hybrid systems are, for all intents and purposes immune to interference. If you are getting a signal it will be clear. They are vulnerable to data loss however, which will result in dropouts. Clipping will likewise result in information loss, not just distortion. Ultimately this could result in an all or nothing situation. Use them when transmission distance will always be relatively short, clarity is key and you have no problems with funding.
All things being equal, the playing field would be easily defined at this point. However things are not all equal here. Within each category you will find a variety of quality and cost, but generally you will indeed get what you pay for. Less expensive systems will have fixed frequencies. A transmitter/receiver system will only work with one frequency that cannot be changed. Better “frequency agile” systems will let you select the channel you desire within a certain range. Some systems will include two antenna (diversity) or indeed two receivers (true diversity), both picking up the same signal. You might look at them and think it’s a gimmick at first. After all, how could one antenna pick up a good signal when another not 8 inches apart cannot? It’s all physics, but in truth though these systems do wonders to mitigate a special type of interference caused when a transmission actually interferes with itself. Other systems will feature “companding” technology, which is a method of signal compression and reconstruction resulting in noise reduction. Technologies like these can greatly improve the outcome.
In practice though many will find that once they have chosen the proper type of system, what will really drive the quality and make life easier are the feature sets found on the better systems. Receivers might contain a squelch function which sets a minimum threshold for audio interference, thus helping to eliminate noise. Some transmitters will contain visual meters, while others will only have a peak indicator light. There are auto scanning receivers that will find a clear frequency and sync transmitters that will dial in for you. Mute buttons and battery meters are other options to look for. Secure channel systems use a code to block eavesdroppers. Let’s not forget build quality and battery life. Is the antenna flexible or rigid? Is it swappable? Rigid may give better range, but it will stick out like a pencil under your talent’s shirt. Can the mic be changed or replaced? These are the things that will really make your life easier, and all of them will probably drive the price up just a little bit.
Am I on?
So now that you have your system, how does it work? While the details will vary slightly, setup for each system is generally the same. Set up your receiver first. If you have the option, set the output of the receiver(s) to the same level (mic or line) as the input on your mixer/recorder and power on.
Next, Install fresh batteries in the transmitter, attach the mic and antennae if necessary and set the transmitter and receiver to the same operating frequency. Again, if you have the option, choose one that is clear of all interference. Walk the transmitter around the outer boundary of your location while listening. If you encounter any areas where a fuzz or hiss creeps in, you’re probably drifting into a space where you’re losing signal. Realigning your receiver antenna or moving it closer or into line of sight will help, as may fresh batteries. As with all audio, keep your equipment away from large electrical sources whenever possible. If you’re hearing strange noises cutting in and out, you probably need to change frequencies.
Transmitter and receiver set to the same channel or frequency
Next you’re going to want to set both the transmission and reception gain. On your transmitter, set the gain so that there is no peaking when your source is at its loudest, but not so low as to introduce hiss. Use the meters if you have them. Do the same for the receivers.
Though wireless mics will quickly become a cherished utility, you’ll quickly learn that it’s best to avoid them if possible. Though they can be a life saver, they can also at times require more attention. Still it’s a long way from two cups and a string and you’ll be happy you’ve invested the time, expense and effort involved in having them in your production arsenal.
Sidebar: Hiding Lavaliers
Lavalier placement on talent is an art, one that is very hard to perfect while making the mechanism invisible. Lavaliers are very sensitive to rubbing of the mic and transmitter wire. Traditional positions for hiding lavalier mics are behind a tie, under the lapel, the brim of a hat (a great parabolic reflector) or center of the chest. Place them where rubbing against skin or clothing is minimized. The mic can be surrounded by moleskin (local drug store) to help minimize friction. You’ll also want to leave a little slack wherever there will be bending or stretching, and then tape the rest of the wire down. The [literal] painful truth is that taping the wire to the body often yields better results than taping to clothing (sweat will be your enemy, consider medical tape). If you find yourself uncomfortable with positioning a mic on talent, prepare your tape and baffling beforehand, then ask them to feed the line and position the wire, then you need only make the final tweaks. Hide the transmitter in pockets, in the small of the back or inside the back of the waistband. Whenever possible, place the mic so that no matter what it is always the same distance from the mouth. If the mic is off one shoulder and the talent turns their head the other way, your audio will suffer.
Sidebar: Practical Usage
On a busy production you may find yourself changing batteries about once a day to be safe. A voltmeter will help you test battery power much more accurately than the meters on the mics. Know that it’s always easier to access your receiver than the transmitter that’s buried in your talent’s clothing. If you’re unsure how loud a scene will get, it’s best to err the transmitter gain on the low side. You can boost and filter at the receiver, but you’ll have to interrupt recording to turn down a transmitter that’s distorting. Make it a point to turn off transmitters between long takes or scene changes and teach the talent where the mute button is. This will save you power and probably save them some embarrassing moments when off set. Also be sure to get your mics back right away, it’s surprising how often talent will leave for home and forget they’re still wearing their mic.
Sidebar: Beware of Old Wireless Mics
With the transition to digital television in June of 2009, the FCC reallocated the frequency range in which wireless mics are allowed to operate. As of June 2010, it is prohibited to use any wireless devices transmitting between the 698 to 806MHz range. If you are using an older system, or are thinking of purchasing one second hand, be sure it can operate outside this range. Transmitting within this range could interfere with emergency services and may result in fines or imprisonment. Note however that if you have a microphone that has variable frequencies of which the 700MHz range is a part, you’re okay as long as you’re not using that range.
To add insult upon injury, the 600MHz range may become an issue in the near future. For more details on either of these issues, check out the FCC website concerning wireless mics, https://www.fcc.gov/encyclopedia/wireless-microphones
Peter Zunitch is an award-winning editor in New York.